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Microsoft 70-513 (TS: Windows Communication Foundation Development with Microsoft .NET Framework 4) exam dumps vce, practice test questions, study guide & video training course to study and pass quickly and easily. Microsoft 70-513 TS: Windows Communication Foundation Development with Microsoft .NET Framework 4 exam dumps & practice test questions and answers. You need avanset vce exam simulator in order to study the Microsoft 70-513 certification exam dumps & Microsoft 70-513 practice test questions in vce format.

An Introduction to the Microsoft 70-513 Exam

The Microsoft 70-513 Exam, officially titled "Windows Communication Foundation Development with Microsoft .NET Framework 4," was a key certification for developers specializing in building service-oriented applications. This exam was designed to validate a developer's ability to design, build, configure, and consume WCF services using the .NET Framework. Passing this exam demonstrated a profound understanding of creating robust, scalable, and interoperable communication systems. It was a testament to a professional's skills in a technology that forms the backbone of many distributed enterprise systems. The curriculum focused on the essential aspects of WCF development, ensuring certified individuals were well-equipped for real-world challenges.

The 70-513 Exam was part of the Microsoft Certified Professional Developer (MCPD) certification track for web and Windows development. It targeted developers with a solid foundation in C# or Visual Basic and experience with Visual Studio. The exam measured proficiency in a wide range of WCF concepts, from the basics of service contracts and endpoints to advanced topics like security, transaction management, and instance management. It was a rigorous test that required both theoretical knowledge and practical application skills. Candidates were expected to know how to not only write the code but also how to configure services using both declarative and programmatic approaches for optimal performance.

While the 70-513 Exam has been retired, the concepts it covered remain highly relevant in the modern development landscape. The principles of service-oriented architecture, message-based communication, and distributed systems are more important than ever. Technologies like Web API and gRPC have evolved from the foundations laid by WCF. Therefore, studying the material associated with the 70-513 Exam provides a deep, historical, and technical context for understanding current service development practices. It offers insights into the evolution of Microsoft's communication technologies and the enduring patterns that govern how applications talk to each other across networks.

Preparing for an exam like the 70-513 Exam involves a structured approach. Candidates typically began by thoroughly reviewing the official exam objectives provided by Microsoft. These objectives detailed every skill measured, such as hosting services, defining bindings, and implementing security protocols. This breakdown allowed developers to create a focused study plan, addressing areas where their knowledge might be weaker. Utilizing a combination of official courseware, hands-on labs, and practice exams was the recommended path to success. This comprehensive preparation ensured candidates were not just memorizing facts but were truly internalizing the concepts and could apply them effectively.

Who Should Take the 70-513 Exam?

The primary audience for the 70-513 Exam consisted of professional developers using Microsoft technologies. Specifically, it was aimed at individuals who had at least two to three years of experience developing web-based or desktop applications using the .NET Framework. These developers were typically looking to specialize in building distributed systems and needed to prove their expertise in Windows Communication Foundation. The certification was a clear indicator to employers that the holder possessed the necessary skills to architect and implement complex, service-oriented solutions that are both secure and reliable in an enterprise environment.

Another key group for this exam were solution architects and technical leads. For these roles, a deep understanding of WCF was crucial for designing scalable and maintainable application architectures. The 70-513 Exam provided a structured way to validate this knowledge. Architects needed to understand the different hosting options, binding types, and security models to make informed decisions that would impact the entire system. Passing the exam demonstrated their ability to design WCF services that meet specific business and technical requirements, ensuring the long-term success of a project and its adherence to industry best practices.

Developers aiming for the prestigious Microsoft Certified Professional Developer (MCPD) certification also found the 70-513 Exam to be a mandatory step. It was a specialization exam within the MCPD track for Windows Developer 4 or Web Developer 4. Achieving the MCPD required passing a series of exams that covered different aspects of .NET development, and WCF was considered a core component of that skill set. For these individuals, the exam was not just about learning a single technology but about completing a comprehensive certification path that represented a high level of overall .NET expertise.

Finally, any developer looking to future-proof their skills would have found value in studying for the 70-513 Exam. While WCF is now considered a legacy technology for new projects, many large enterprises still maintain and extend existing systems built upon it. Understanding WCF is therefore a valuable skill for contract work and for roles in organizations with significant investments in .NET. The fundamental principles of contracts, bindings, and behaviors taught in the 70-513 Exam curriculum are also transferable to newer technologies, providing a strong foundation for learning modern service development frameworks.

Core Technologies Covered in the 70-513 Exam

The centerpiece of the 70-513 Exam was, without a doubt, Windows Communication Foundation (WCF). WCF is a unified programming model for building service-oriented applications. The exam covered the entire WCF stack, from the ground up. Candidates were tested on their ability to define service contracts, data contracts, and message contracts. This involved understanding how to use attributes like ServiceContract, OperationContract, and DataContract to create the public interface of a service. A firm grasp of these core concepts was essential, as they form the very foundation of any WCF application.

Another critical technology area was the configuration of WCF services. The 70-513 Exam required deep knowledge of how to set up endpoints, which consist of an address, a binding, and a contract (the "ABC" of WCF). Candidates had to be proficient in configuring these elements in both the app.config or web.config files and programmatically in code. This included understanding the wide array of standard bindings provided by WCF, such as BasicHttpBinding, WSHttpBinding, and NetTcpBinding, and knowing when to use each one based on the specific requirements for interoperability, performance, and security.

Security was a major component of the 70-513 Exam. Developers needed to demonstrate their ability to secure WCF services using various mechanisms. This included understanding the concepts of transport security, message security, and mixed-mode security. Candidates were expected to know how to configure authentication, authorization, and message protection using credentials like Windows accounts, X.509 certificates, and username/password tokens. Implementing robust security is a non-negotiable requirement for enterprise applications, and the exam thoroughly vetted these critical skills to ensure certified professionals could build trustworthy systems.

The exam also delved into more advanced WCF features. These included transaction management, reliable messaging, and instance management. Candidates needed to understand how to ensure that a series of operations either all succeed or all fail together, maintaining data integrity across distributed systems. They also had to know how to configure services to handle different instancing models, such as per-call, per-session, and singleton, and understand the performance and scalability implications of each choice. Mastery of these advanced topics distinguished a proficient WCF developer from a novice and was a key focus of the 70-513 Exam.

Exam Structure and Question Formats

The 70-513 Exam followed a standard format for Microsoft certification tests of its era. It typically consisted of between 40 to 60 questions, and candidates were allotted a specific amount of time, usually around two to three hours, to complete it. The exam was designed to be challenging, requiring a deep and practical understanding of the subject matter rather than simple memorization. The questions were carefully crafted to simulate real-world scenarios that a WCF developer would encounter in their daily work, ensuring that the certification was a true measure of professional competence.

A variety of question formats were used in the 70-513 Exam to test knowledge in different ways. Multiple-choice questions were common, which could have a single correct answer or multiple correct answers. There were also "drag-and-drop" questions, where candidates had to correctly order a sequence of steps or match concepts with their descriptions. This format was particularly effective for testing knowledge of processes, such as the steps involved in configuring a specific WCF binding or security setting. These interactive question types made the exam more engaging and tested practical application skills more effectively.

Case studies were another significant part of the 70-513 Exam. In this format, candidates were presented with a detailed description of a business problem or a technical scenario. This would be followed by a series of questions related to the case study. To answer correctly, one had to carefully analyze the provided information, including business requirements, technical constraints, and code snippets. This format tested a candidate's ability to apply their knowledge to a larger, more complex problem, mirroring the kind of analytical and problem-solving skills required in a senior developer or architect role.

Finally, the exam might include questions that required building or completing code. These questions would present a code snippet with missing sections, and the candidate would have to choose the correct code from a list of options to complete the logic. This was a direct test of a developer's coding proficiency and their familiarity with the WCF class library and syntax. Successfully answering these questions required not just knowing the theory but having hands-on experience writing and debugging WCF applications in Visual Studio, making practical preparation a crucial component of any study plan for the 70-513 Exam.

The Importance of WCF in the 70-513 Exam

Windows Communication Foundation (WCF) was the absolute heart of the 70-513 Exam. The entire certification was built around this single technology, underscoring its importance in the Microsoft development ecosystem at the time. WCF was Microsoft's comprehensive framework for building distributed applications, designed to unify and replace a collection of older communication technologies like ASMX web services, .NET Remoting, and MSMQ. The exam was created to ensure that developers had mastered this unified model, enabling them to build services that were interoperable, secure, and reliable, regardless of the underlying transport protocol.

The exam's focus on WCF was a reflection of the industry's shift towards Service-Oriented Architecture (SOA). WCF provided a powerful and flexible implementation of SOA principles on the .NET platform. The 70-513 Exam tested a developer's ability to think in terms of services, contracts, and messages. It required candidates to understand how to design loosely coupled systems where different components could communicate seamlessly. This skill was highly valued in enterprise environments where applications needed to integrate with a variety of other systems, both internal and external, often built on different technology stacks.

One of the key reasons for WCF's prominence in the 70-513 Exam was its flexibility. WCF was designed to be highly configurable. The same service could be exposed over different endpoints, each with a different address, binding, and contract. This meant a single service could simultaneously communicate with a legacy Java application over SOAP, a modern .NET client over TCP, and a web browser over RESTful HTTP. The exam heavily emphasized a developer's ability to understand and configure these different bindings and behaviors to meet diverse communication requirements, a core strength of the WCF framework.

Furthermore, the 70-513 Exam's deep dive into WCF covered essential non-functional requirements that are critical for enterprise-grade applications. Topics like distributed transactions, reliable messaging, and advanced security configurations were central to the curriculum. These are features that are complex to implement from scratch but are provided out-of-the-box by WCF. The exam ensured that certified professionals knew how to leverage these powerful capabilities correctly, enabling them to build applications that were not just functional but also robust, secure, and scalable enough to meet the demands of modern business.

Navigating Windows Communication Foundation

Navigating the complexities of Windows Communication Foundation was the primary challenge for any candidate preparing for the 70-513 Exam. At its core, WCF is built around the "ABCs": Address, Binding, and Contract. The Address specifies where the service is located. The Binding defines how the service communicates, including the transport protocol (like HTTP or TCP), the encoding (like text or binary), and any security settings. The Contract specifies what the service can do, defining the operations it exposes. A deep and intuitive understanding of how these three components work together was the first and most critical step.

A significant part of navigating WCF involves mastering its configuration. WCF services can be configured either declaratively in XML configuration files (app.config or web.config) or programmatically in code. The 70-513 Exam required proficiency in both methods. Declarative configuration is powerful because it allows administrators to change service settings without recompiling the application. Programmatic configuration, on the other hand, offers more flexibility for dynamic scenarios. Candidates had to know the syntax and structure of the <system.serviceModel> configuration section and the corresponding C# or VB.NET classes for setting up services and clients.

Understanding the WCF channel stack was another key aspect. WCF processes messages through a stack of channels, where each channel is responsible for a specific task, such as encoding, transport, or security. While developers often work with the high-level abstractions of bindings, the 70-513 Exam expected a deeper understanding of this underlying architecture. This knowledge was crucial for troubleshooting communication issues and for creating custom bindings or behaviors to handle unique scenarios. Knowing how messages flow through the channel stack provided the insight needed to diagnose and solve complex WCF problems.

Finally, effective navigation of WCF required a solid grasp of service behaviors and instance management. Behaviors allow developers to modify the runtime behavior of a service without changing the service code itself. This could include adding custom message inspectors, enabling metadata publishing, or controlling throttling to manage server load. Similarly, understanding the difference between per-call, per-session, and singleton instancing modes was vital for designing services that are both scalable and manage state correctly. The 70-513 Exam tested these concepts thoroughly, ensuring developers could build well-architected and efficient WCF applications.

Designing and Defining Contracts: The Blueprint of Your Service

In the world of the 70-513 Exam, contracts are the most fundamental concept in Windows Communication Foundation. They are the formal agreement between a service and a client, defining the rules of engagement. The service contract, marked with the ServiceContract attribute, is the primary blueprint. It specifies the operations that the service exposes to the outside world. Each method within the service contract interface that is intended to be a callable operation must be decorated with the OperationContract attribute. This explicit declaration creates a clear and unambiguous definition of the service's capabilities, which is essential for achieving loose coupling.

Beyond the service contract, the 70-513 Exam placed significant emphasis on data contracts. When complex data types are passed as parameters or return values in service operations, they must be defined as data contracts. This is achieved by applying the DataContract attribute to a class and the DataMember attribute to the properties or fields that should be included in the serialization process. This mechanism allows WCF to translate .NET objects into a standard, interoperable format like XML, which can be understood by clients on any platform. Mastery of data contracts was crucial for building services that could exchange rich data structures.

A less common but equally important type of contract covered in the exam was the message contract. While data contracts control the serialization of the body of a message, message contracts provide direct control over the entire SOAP message structure. By applying the MessageContract attribute to a class, developers can specify which data should go into the SOAP headers and which should go into the body. This level of control is necessary for interoperability with services that expect a specific message format or for implementing custom security headers. The 70-513 Exam tested the ability to use message contracts for these advanced scenarios.

Finally, the concept of fault contracts was a key part of service design. By default, any unhandled exception in a WCF service will cause a generic FaultException to be sent to the client, which can hide important details. Fault contracts, defined using the FaultContract attribute on an operation, allow developers to specify custom, strongly-typed exceptions that can be formally communicated to the client. This enables robust error handling on the client side, as the client can write specific catch blocks for different types of service faults. The 70-513 Exam required developers to know how to implement this structured error-handling mechanism.

A Deep Dive into WCF Bindings

Bindings are a cornerstone of WCF and a major topic in the 70-513 Exam. A binding is a collection of binding elements that define how a client and service communicate with each other. It specifies the transport protocol, the message encoding, and various other communication details like security, reliability, and transaction flow. WCF provides a set of pre-configured, standard bindings that cover the most common communication scenarios. Understanding the purpose and characteristics of each standard binding was essential for success on the exam. For example, BasicHttpBinding is designed for maximum interoperability with older ASMX web services.

For scenarios requiring more advanced features and security, the 70-513 Exam focused on bindings like WSHttpBinding. This binding supports a wide range of WS-* standards, including reliable messaging, transactions, and robust message-level security. It is suitable for building secure and reliable services that communicate over the internet. In contrast, for high-performance communication between .NET applications within a corporate network, NetTcpBinding is the optimal choice. It uses a binary encoding and the TCP protocol, resulting in significantly faster communication than the HTTP-based bindings. Candidates were expected to know when to choose one binding over another.

The exam also covered bindings designed for specific use cases. NetMsmqBinding, for instance, is used for durable, disconnected communication using Microsoft Message Queuing (MSMQ). This is ideal for scenarios where the client and service may not be online at the same time. The message is placed in a queue and processed by the service when it becomes available. Another specialized binding is NetPeerTcpBinding, which enables multi-party peer-to-peer communication directly between clients without a central server, useful for collaborative applications. The 70-513 Exam required knowledge of these specialized bindings and their appropriate applications.

Beyond using the standard bindings, the 70-513 Exam tested the ability to create custom bindings. A custom binding is constructed by manually assembling a set of binding elements in a specific order. This provides the ultimate level of control and flexibility, allowing a developer to create a communication stack tailored to very specific needs that are not met by any of the standard bindings. This could involve adding a custom logging channel, using a non-standard transport, or combining different security and encoding options. Demonstrating the ability to create a custom binding was a sign of true WCF mastery.

Configuring Endpoints: The Gateway to Your Service

Endpoints are where the "ABCs" of WCF—Address, Binding, and Contract—come together. An endpoint is the physical manifestation of a service that clients can connect to. A single WCF service can expose multiple endpoints, and this was a key concept for the 70-513 Exam. This allows the same service logic to be accessible to different types of clients. For example, a service could have one endpoint using BasicHttpBinding for legacy clients and another endpoint using NetTcpBinding for high-performance internal .NET clients. Each endpoint provides a distinct gateway into the service.

The configuration of these endpoints was a critical skill tested by the 70-513 Exam. As mentioned earlier, this can be done either declaratively in a configuration file or programmatically in code. The XML-based configuration in app.config or web.config was a major focus. Candidates needed to be fluent in the syntax of the <system.serviceModel> section. This involved defining <service> elements, and within them, <endpoint> elements. Each endpoint element specifies its address, binding, and contract attributes. Knowing how to correctly structure this configuration was non-negotiable for passing the exam.

Programmatic configuration of endpoints offers greater flexibility, especially in scenarios where the endpoint details are not known at design time. The 70-513 Exam required developers to know how to use the ServiceHost class to add endpoints in code. This involves creating an instance of ServiceHost, and then calling its AddServiceEndpoint method, passing in the contract type, a binding object, and the address string. This approach is common in self-hosted WCF services, where the service is running in a console application or a Windows Service instead of being hosted in IIS.

The exam also covered the concept of default endpoints. In .NET Framework 4 and later, WCF introduced a simplified configuration model. If a service host is created without any endpoints explicitly configured, WCF will automatically add default endpoints for each service contract implemented by the service. It creates one endpoint for each base address specified for the service. While this simplifies development, the 70-513 Exam required a deeper understanding of how these defaults are created and how they can be customized, ensuring developers could control the service's exposure even when relying on convention-based configuration.

Hosting WCF Services

A WCF service is just a class library until it is hosted in a running process. The 70-513 Exam thoroughly tested the different options available for hosting WCF services. The most common hosting environment for HTTP-based services is Internet Information Services (IIS). Hosting in IIS provides numerous benefits, such as process recycling, idle shutdown, and robust management tools. When a service is hosted in IIS, it is activated automatically when the first message arrives. Candidates needed to understand how to create the necessary .svc file and configure the web.config file for IIS hosting.

Another powerful hosting option covered in the exam is Windows Process Activation Service (WAS), often referred to as "IIS without the HTTP." WAS, introduced with Windows Vista and IIS 7, extends the process activation model of IIS to non-HTTP protocols. This means that services using NetTcpBinding or NetMsmqBinding can benefit from the same features as HTTP services, such as on-demand activation and application pooling. The 70-513 Exam required knowledge of how to configure WAS to host services over different protocols, which is a key skill for enterprise-level deployments.

Self-hosting is the third major hosting model. In this scenario, the WCF service is hosted within a developer-managed process, such as a console application, a Windows Forms application, or a Windows Service. This provides maximum control over the lifetime of the host process. The developer is responsible for creating an instance of the ServiceHost class, opening it to start listening for messages, and closing it to shut down the service gracefully. The 70-513 Exam tested the ability to write the code required to self-host a service, including handling the host's lifecycle and configuring its base addresses and endpoints programmatically.

Finally, the exam touched upon hosting within a Windows Service. This is a common choice for self-hosted services that need to run continuously in the background, even when no user is logged in. It combines the control of self-hosting with the reliability and manageability of a Windows Service. Candidates were expected to know how to create a Windows Service project, integrate the ServiceHost logic within the OnStart and OnStop methods of the service, and use command-line tools like installutil.exe to install and manage the service. This represents a robust and production-ready hosting solution for many WCF applications.

Instance Management and Concurrency

Instance management is a critical concept in WCF that determines how service objects are created in response to client requests. The 70-513 Exam tested the three main instancing modes, which are controlled by the InstanceContextMode property of the ServiceBehavior attribute. The default mode is PerCall, where a new service object is created for every single client request. This is a highly scalable and stateless model, as it minimizes memory usage on the server. However, it means that no state can be maintained in the service object between calls.

The second mode, PerSession, creates a new service object for each new client session. This session is maintained for as long as the client proxy is open (and the binding supports sessions, like NetTcpBinding or WSHttpBinding). This mode is useful when a service needs to maintain state specific to a particular client across multiple calls. For example, a shopping cart service would likely use a per-session instance mode. The 70-513 Exam required candidates to understand the lifecycle of these sessionful objects and the binding requirements to enable them.

The third and final mode is Singleton. In this mode, a single service object handles all requests from all clients for the entire lifetime of the application. This is useful for services that need to share global state. However, it introduces significant concurrency challenges. Since a single object is handling multiple requests simultaneously, the developer is responsible for managing thread safety to prevent data corruption. The 70-513 Exam stressed the importance of understanding the scalability and threading implications of choosing the singleton mode.

Closely related to instance management is concurrency control, which is managed by the ConcurrencyMode property. The default is Single, which means only one request is processed by a service instance at a time. WCF locks the instance and queues other requests. Multiple allows multiple requests to be processed concurrently by the same service instance on different threads, which requires the developer to make their code thread-safe. Reentrant is a variation of single-threaded access that allows the service to make outbound calls and have them call back into the same service without causing a deadlock. The 70-513 Exam tested the interplay between these modes and the instance context mode.

Implementing WCF Security

Security is not an optional feature in enterprise applications; it is a fundamental requirement. The 70-513 Exam placed a heavy emphasis on a developer's ability to secure WCF services. The WCF security model is comprehensive and can be complex, covering authentication, authorization, and message integrity and confidentiality. The first layer of this model is the security mode, which can be transport-level, message-level, or a combination of both. Transport security, provided by protocols like HTTPS or SSL over TCP, encrypts the entire communication channel. It is point-to-point and generally easier to configure.

Message security, on the other hand, operates at the SOAP message level. It encrypts and signs parts of the message itself, rather than the entire transport channel. This provides end-to-end security, meaning the message remains secure even if it passes through multiple intermediaries before reaching its final destination. Message security is more flexible but also more computationally intensive. The 70-513 Exam required candidates to understand the trade-offs between transport and message security and how to configure them using the appropriate binding settings, such as the security element in a binding configuration.

Authentication is the process of verifying a client's identity. WCF supports a wide range of client credential types, and the 70-513 Exam tested knowledge of the most common ones. These include Windows credentials (for intranet scenarios), username/password combinations, and X.509 certificates. Candidates had to know how to configure a service to expect a certain type of credential and how to provide that credential on the client side. This involved setting the clientCredentialType attribute in the binding configuration and manipulating the client proxy's ClientCredentials property in code.

Once a client is authenticated, authorization determines what they are allowed to do. The 70-513 Exam covered WCF's role-based authorization capabilities. This often involves using the PrincipalPermission attribute to declaratively restrict access to service operations based on a user's identity or their membership in a specific Windows group or custom role. For more dynamic authorization logic, developers can programmatically check the identity of the caller within the service method by inspecting the ServiceSecurityContext.Current. A thorough understanding of these authorization techniques was crucial for building secure and robust services.

Managing Transactions in a Distributed Environment

Transactions are essential for maintaining data consistency, especially in distributed systems where an operation might involve updating multiple resources. The 70-513 Exam required a deep understanding of how WCF integrates with transaction processing systems to enable distributed transactions. WCF leverages the Microsoft Distributed Transaction Coordinator (MSDTC) to coordinate transactions that span across service boundaries, databases, and message queues. The key to enabling this is to use a binding that supports transaction flow, such as WSHttpBinding or NetTcpBinding.

To participate in a transaction, a service operation must be configured to allow or require it. This is done using the TransactionFlow attribute on the operation contract. The developer can specify whether a transaction is Mandatory, Allowed, or NotAllowed. On the client side, the code that calls the service operation must be wrapped in a TransactionScope. When the transaction scope is created, an ambient transaction is established. If the binding is configured for transaction flow, this transaction is then propagated with the WCF message to the service. The 70-513 Exam tested the ability to configure both the client and service correctly.

Inside the service operation, the implementation logic must enlist in the incoming transaction. This is controlled by the OperationBehavior attribute's TransactionScopeRequired property. If set to true, a new transaction scope will be created for the operation, and if a transaction was flowed from the client, the operation will join that existing transaction. Any work done within this scope, such as database updates, will become part of the distributed transaction. If any part of the operation fails, the entire transaction can be rolled back across all participating resources.

The ServiceBehavior attribute also plays a role in transaction management. Its TransactionIsolationLevel property can be used to specify the isolation level for new transactions created at the service boundary. Furthermore, the ReleaseServiceInstanceOnTransactionComplete property can be used to control the lifetime of the service instance in relation to the transaction. Setting this to true can help to release server resources more quickly. The 70-513 Exam required a comprehensive understanding of these attributes and how they work together to create reliable, transactional services that ensure data integrity across the enterprise.

Ensuring Reliable Messaging

In many business scenarios, it is critical that messages sent from a client are guaranteed to arrive at the service, and in the correct order. Standard network protocols like HTTP and TCP do not provide this guarantee by themselves; a lost network packet can result in a lost message. The 70-513 Exam covered the WS-ReliableMessaging protocol, which WCF implements to solve this problem. When reliable messaging is enabled, a source and destination endpoint establish a reliable session. Messages are sent with sequence numbers, and acknowledgments are used to confirm receipt.

Enabling reliable messaging in WCF is primarily a matter of configuration. It is a property of the binding. Bindings like WSHttpBinding and NetTcpBinding have a reliableSession element in their configuration that can be enabled. Candidates for the 70-513 Exam needed to know how to enable this feature and configure its properties, such as the inactivityTimeout, which determines how long a session can be idle before it is terminated, and the ordered property, which specifies whether messages must be processed in the order they were sent.

The reliable session has a specific lifecycle. It is created when the client proxy is first opened and established through a handshake between the client and the service. Once the session is established, messages can be exchanged reliably. The session is terminated when the client proxy is closed. Understanding this lifecycle was important for the exam, as it has implications for how client proxies are managed. For example, if a client application crashes without closing the proxy properly, the reliable session may time out on the server, releasing resources.

While reliable messaging provides a powerful guarantee, it also introduces overhead. The additional messages for session management and acknowledgments can impact performance. Therefore, it should only be used when the business requirements truly demand it. The 70-513 Exam expected developers to have the judgment to know when to apply reliable messaging. It is ideal for long-running business processes or for communication over unreliable networks where message loss is a real possibility. For simple request-response operations over a stable local network, the overhead might not be justified.

Working with Data: Serialization and Validation

How WCF handles data is a core topic, and the 70-513 Exam delved into the details of serialization. Serialization is the process of converting an in-memory .NET object into a format that can be transmitted over a network, such as XML or binary. WCF's default serializer is the DataContractSerializer. As discussed previously, this serializer works on an opt-in basis, meaning only members explicitly marked with the DataMember attribute are included. The exam required a thorough understanding of how to apply the DataContract and DataMember attributes to control the serialization process.

The DataContractSerializer has several features that were tested in the 70-513 Exam. For example, the Order property of the DataMember attribute can be used to control the order in which elements appear in the serialized XML. The IsRequired property can be used to indicate that a data member must be present when a message is deserialized. The Name property allows a developer to specify a different name for the member in the serialized output than the one used in the .NET class. These features are crucial for versioning data contracts and for interoperating with systems that have specific schema requirements.

While DataContractSerializer is the default, WCF also supports other serializers. The exam expected awareness of the XmlSerializer, which was the serializer used in older ASMX web services. The XmlSerializer provides more control over the resulting XML shape and uses an opt-out model, but it is less performant. Candidates needed to know how to switch to the XmlSerializer by applying the XmlSerializerFormat attribute to the service contract. Another option is the NetDataContractSerializer, which includes .NET type information in the serialized data, but this is generally discouraged as it creates a tight coupling between the client and service.

Data validation is another critical aspect of working with data. While WCF itself does not have a built-in validation framework, the 70-513 Exam expected candidates to know how to implement validation logic. A common approach is to perform validation within the service operation itself before processing the data. If the data is invalid, the service can throw a FaultException to inform the client of the problem. For more complex scenarios, developers can integrate with validation frameworks or use techniques like parameter inspectors to centralize validation logic, ensuring that invalid data is rejected early in the message processing pipeline.

Advanced WCF Service Behaviors

Behaviors are a powerful extensibility mechanism in WCF that allow developers to inspect or modify the runtime execution of a service. The 70-513 Exam required knowledge of how to apply and create various types of behaviors. Service behaviors, applied with the ServiceBehavior attribute, affect the entire service. We have already seen how this attribute is used to control instancing, concurrency, and transactions. It can also be used to configure things like metadata publishing through the HttpGetEnabled property of the ServiceMetadataBehavior, or to control how exceptions are handled via the IncludeExceptionDetailInFaults property for debugging purposes.

Endpoint behaviors affect a specific endpoint. They can be configured in the <endpointBehaviors> section of the configuration file or added to an endpoint's Behaviors collection in code. An example of a built-in endpoint behavior is the clientVia behavior, which is used in routing scenarios to specify the ultimate destination of a message. The 70-513 Exam expected candidates to know how to apply these behaviors to tailor the functionality of individual endpoints without affecting the entire service.

Operation behaviors, applied with the OperationBehavior attribute, modify the execution of a specific service operation. We have already discussed its role in transaction management with the TransactionScopeRequired property. Another key property is Impersonation, which controls whether the service operation executes under the client's identity. This is a critical security feature in intranet applications that use Windows authentication. Understanding how to set the impersonation level correctly was a key skill tested by the 70-513 Exam.

Finally, the exam covered the creation of custom behaviors. This is an advanced topic that demonstrates a deep understanding of the WCF runtime. A custom behavior typically implements an interface like IServiceBehavior or IEndpointBehavior. Within the implementation, the developer can add custom dispatchers or inspectors to the WCF runtime. For example, a custom message inspector could be used to log every incoming and outgoing message, or a custom parameter inspector could be used to implement a centralized validation logic. The ability to write and install these custom extensions was a hallmark of a true WCF expert.

Creating and Configuring WCF Clients

Consuming a WCF service is just as important as creating one, and the 70-513 Exam dedicated a significant portion of its objectives to the client-side of the communication equation. The first step in creating a client is to generate a proxy class. This can be done using the "Add Service Reference" feature in Visual Studio or with the command-line tool, svcutil.exe. This process reads the service's metadata (its WSDL) and generates a .NET class that mirrors the service contract. This proxy class handles the complex work of serializing data, creating messages, and sending them over the network.

Once the proxy is generated, the client application needs to be configured with an endpoint that matches one of the endpoints exposed by the service. This client-side configuration is typically done in the app.config or web.config file of the client application. The configuration file will contain a <client> section within the <system.serviceModel> block. Inside this section, there will be an <endpoint> element for each service the client needs to communicate with. This element specifies the same "ABC"s—address, binding, and contract—as the service endpoint. The 70-513 Exam required proficiency in creating this client configuration.

In code, the client application creates an instance of the generated proxy class. The constructor of this proxy class often takes the name of the endpoint configuration as a parameter. For example, MyServiceClient client = new MyServiceClient("NetTcpBinding_IMyService");. Once the client object is created, calling methods on it is as simple as calling methods on any other local object. The proxy handles the underlying communication transparently. The 70-513 Exam tested the entire lifecycle of the client proxy, including the importance of properly closing it to release resources.

It is crucial to handle the closing of the client proxy correctly. A common mistake is to wrap the client instance in a using block. This is problematic because if a fault occurs during communication, the Dispose method (which calls Close) can throw a second exception, masking the original problem. The recommended practice, and a key point for the 70-513 Exam, is to use a try...catch...finally block. The Close method is called in the try block, and if an exception occurs, the Abort method is called in the catch or finally block to ensure the connection is terminated without causing further errors.

Handling Asynchronous Communication

In many client applications, especially those with a user interface, it is essential to call service operations asynchronously. A synchronous call will block the UI thread while waiting for the service to respond, making the application appear frozen and unresponsive. The 70-513 Exam tested the various patterns for asynchronous programming available in WCF. When generating the proxy using "Add Service Reference," there is an option to generate asynchronous method pairs for each service operation, such as BeginMyOperation and EndMyOperation. This is the Asynchronous Programming Model (APM) pattern.

Using the APM pattern involves calling the Begin method, passing in a callback delegate and a state object. The Begin method returns immediately, freeing up the UI thread. When the service operation completes, WCF invokes the provided callback delegate on a background thread. Inside the callback, the developer calls the corresponding End method to retrieve the return value and handle any exceptions that occurred during the service call. The 70-513 Exam required candidates to be proficient in writing code that followed this pattern, including marshalling results back to the UI thread if necessary.

Another pattern available is the Event-based Asynchronous Pattern (EAP). When the proxy is configured to generate event-based asynchronous operations, it will have methods like MyOperationAsync and an event called MyOperationCompleted. The developer calls the MyOperationAsync method and subscribes to the Completed event. When the operation finishes, the event is raised, and the event handler can access the results or any errors through the event arguments. This pattern is often considered more intuitive and easier to use than the APM pattern, especially in Windows Forms or WPF applications.

With the introduction of .NET Framework 4, the Task-based Asynchronous Pattern (TAP), using the Task and Task<T> classes, became the preferred model for asynchrony. When generating a client proxy, it's possible to generate TAP-based asynchronous methods that return a Task. This allows the client to use the async and await keywords, which dramatically simplifies asynchronous code. The developer can await the result of the service call, and the compiler handles all the complex callback and state management logic. The 70-513 Exam, being focused on .NET 4, placed importance on this modern and simplified approach to asynchronous service consumption.

Routing and Discovery

In large, complex enterprise environments, services are not always called directly. A message might need to pass through intermediaries for logging, load balancing, or protocol bridging. The 70-513 Exam covered the WCF Routing Service, a powerful and configurable component that acts as a generic SOAP intermediary. The Routing Service can be configured to receive messages and forward them to one or more destination services based on the message content or other criteria. This allows for the creation of flexible and dynamic service architectures.

The configuration of the Routing Service is done declaratively in its app.config file. The core of the configuration is the routing table, which is a set of filters. Each filter defines a condition, for example, matching a specific SOAP action or an XPath query on the message body. Each filter is associated with a list of destination client endpoints. When a message arrives, the Routing Service evaluates the filters in the table. If a message matches a filter, it is forwarded to the corresponding destination endpoint(s). The 70-513 Exam tested the ability to create these filter tables to implement various routing scenarios.

Another advanced topic covered was WCF Discovery. In a dynamic environment, the physical location (address) of a service might change. WCF Discovery provides a mechanism for services to announce their presence on the network and for clients to find services dynamically at runtime without needing a hard-coded address. This is based on the WS-Discovery protocol. A service can be made "discoverable" by adding a service discovery behavior to its configuration. It will then broadcast "Hello" messages when it starts and "Bye" messages when it stops.

Clients can find services by sending out a probe message. Any discoverable services that match the probe's criteria (such as the service contract) will respond with their address. This allows for a much more loosely coupled system where clients do not need to be reconfigured if a service moves to a different server. The 70-513 Exam required an understanding of how to configure both services and clients to participate in this discovery process. It also covered the concept of a Discovery Proxy, which can act as a centralized repository of service information to reduce network broadcast traffic.

Message Exchange Patterns

The way a client and service exchange messages is defined by the Message Exchange Pattern (MEP). The 70-513 Exam covered the three primary MEPs supported by WCF. The default and most common pattern is Request-Reply. In this pattern, the client sends a request message and then waits for a reply message from the service. This is a synchronous-style communication, even if called asynchronously from the client's perspective. It is modeled by a service operation that has a return value (even if it's void, a reply message is still sent to acknowledge receipt).

The second MEP is One-Way. In this pattern, the client sends a message to the service but does not expect or wait for any reply. This is a "fire and forget" style of communication. To define a one-way operation in WCF, the IsOneWay property of the OperationContract attribute is set to true. This pattern is useful for notifications or logging events where the sender does not need confirmation of receipt. However, the 70-513 Exam emphasized that a one-way call does not guarantee delivery; if a reliable transport or reliable messaging is not used, the message could be lost.

The third and most complex MEP is Duplex (or Callback). This pattern allows a service to communicate back to the client through a callback channel, independent of any specific operation call. It enables two-way, peer-to-peer style conversations. To implement a duplex service, the ServiceContract attribute must specify a CallbackContract. The client, when it connects, provides an implementation of this callback contract. The service can then call methods on the client's callback contract at any time. This pattern requires a binding that supports duplex communication, such as WSDualHttpBinding or NetTcpBinding. The 70-513 Exam tested the ability to define and implement these callback contracts.

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