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Different transport schemas supported by WCF include: 

• HTTP
• TCP
• Peer network
• IPC
• MSMQ

WCF is a unified programming model designed by Microsoft to build service-oriented applications. The framework allows developers to DEVELOP secure, reliable, transacted solutions which can be integrated across platforms and interoperated with existing ones. The above-given QUESTIONS are crucial for understanding WCF (Windows communication foundation). You will also find an overview of WCF's important FEATURES, pros, and cons, which will help you prepare better. The goal is to help you get your dream JOB in your next interview.

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Services often use a technique called impersonation to restrict client ACCESS to a service DOMAIN's resources. In WCF, impersonation is disabled by default, and services are accessed via the PROCESS identity of the WCF service. 

For troubleshooting unexpected problems in applications, exception HANDLING is essential. Exception handling is a feature of OBJECT programming languages and it is an ERROR that occurs during execution. In WCF, there are three ways to handle exceptions:  

returnUnknownExceptionsAsFaults: Debugging Mode  
FaultException: Best OPTION  
IErrorHandler: Only when Fault cannot handle the exception 

WCF Data Services is basically a platform for what Microsoft CALLS Data Services. Tabular data can be exposed as a set of REST APIs, allowing standard HTTP VERBS such as GET, POST, PUT, and DELETE to be used. The OData PROTOCOL is used by WCF Data Services for addressing and UPDATING resources. 

In essence, MSMQ (Microsoft Messaging Queue) is a technology used for asynchronous communications. MSMQ is also capable of inter-process communication. MSMQ is very useful when two processes WISH to COMMUNICATE in a "Fire and Forget" MANNER.  MSMQ is basically developed by Microsoft and is deployed in the Windows operating system. It facilitates communication across heterogeneous networks and systems that might be a BIT offline from time to time.

MEP (Message Exchange Pattern) is a way of communicating between clients and SERVERS in WCF. MEP is one of the greatest features of WCF. The three types of MEPs supported by WCF are as follows:  

• Request-Reply: Request-Reply is WCF's default communication pattern. 
• One-way: Using this pattern MEANS you don't expect to receive a response BACK from the SERVICE after it performs a certain operation.  
• Duplex: Duplex is a two-way communication way. The duplex MEP is applicable when the client initiates a long-running process with the service and the service requires notification. 

In WCF, the transport SECURITY mechanisms are dependent on the binding and transport that is USED. It ensures the message passes securely from the client to the service over a transport medium. This point-to-point security is ESTABLISHED USING SSL (Secure Socket Layer). Integrity, privacy, and authentication are the goals of transport-level security.

Images, .pdf FILES, and large documents can all be transferred using WCF.  Streaming is the best and most common method of ACHIEVING this. Streaming allows the recipient of a message (either a client or a service) to begin processing the message before it has completed receiving the entire message. With STREAMED transfers, there's no need to keep large MEMORY buffers in the background, so scalability is IMPROVED. 

Throttling is derived from the keyword throughput, which means work that is PERFORMED at specific intervals of time. We can limit the number of instances or SESSIONS created at the APPLICATION level USING the properties like maxConcurrentCalls, maxConcurrentInstances, and maxConcurrentSessions provided by WCF throttling. Performance is boosted by using it.

Different address FORMAT of WCF INCLUDE: 

• HTTP Address Format: http:// LOCALHOST: 
• TCP Address Format: net.tcp://localhost: 
• MSMQ Address Format: net.msmq://localhost:

WCF USES the DataContractSerializer class as its default serializer. Other serialization PURPOSES can be served by this serializer. Using the DataContractAttribute and DataMemberAttribute attributes, we can also EXPLICITLY CREATE a data contract.

Example: 
DataContractSerializer dataContractSerializer = new  DataContractSerializer(TYPEOF(MyTestClassType)); 

There are several types of BINDING available in WCF, including:

• BASIC HTTP Binding 
• NetTcp Binding 
• WSHttp Binding 
• NetMsmq Binding 
• NetNamedPipeBinding 
• WSDualHttp Binding 
• MsmqIntegration Binding 
• NetMsmq Binding 
• WSFederationHttp Binding 
• NetPeerTcp Binding 

WCF bindings consist of a NUMBER of binding elements, which specify how service and client will communicate. Clients use bindings based on their NEEDS. THEREFORE, binding is BASICALLY a way for clients and services to communicate in accordance with the client's needs. It supports a variety of protocol types that can be used for communication with clients and different types of encodings for transmitting data over the INTERNET.

To access WCF service, “System.ServiceModel” is USED. It provides CLASSES that relate to service models. The namespace contains the types NECESSARY for BUILDING WCF services and CLIENT applications.

WCF provides three ways to control WCF instance creation as follows: 

• Per Call: A NEW instance will be created for each request from the same client or a new one, which means that every request will be a new request. Although this mode is most efficient in terms of MEMORY, a session still needs to be maintained.  
• Per Session: A new instance would be created for each new client session, and the SCOPE of that OBJECT would correspond to the scope of that session.  
• Single Instance: For each SERVICE object, only one instance will be created for all requests, regardless of whether they are coming from the same client or not. This is the least efficient instance mode in terms of memory usage. 

WCF USES an INSTANCE MANAGEMENT approach to bind a set of messages (client requests) to a set of service instances. The need for Instance Management is crucial since the demands of applications vary too much in terms of SCALABILITY, throughput, transactions, queues, and performance. Therefore, ONE solution does not fit all applications.

In WCF, a transaction is a set of operations that follow certain properties, COLLECTIVELY REFERRED to as ACID. In the case of a single failure, the entire system falls apart. A transaction occurs when an order is placed online. Atomic and long-running transactions are two TYPES of transactions.