WCF Interview Questions And Answers

WCF Interview Questions

Received notification from your dream company, or aspiring to be a WCF engineer in a software firm, interviews are a vital part of your selection process. How to prepare for a WCF interview is a highlighted question asked by hundreds of newbies. To help you crack the approaching interview here’s a list of 15 WCF Interview Questions with short answers to provide an edge to answer those questions.

Window Communication Foundation

WCF is a framework available free of cost to build service-oriented applications. The framework was introduced by Microsoft fifteen years ago on November 21, 2006. The program was previously known as Indigo. WCF is an open-source runtime tool preferably built by principles derived from Service Oriented Architecture. The services produced have a WDSL (Web Services Description Language)  interface and supports interoperability. The data transfer is managed through endpoints.

 Top 10 interview questions for WCF 

  1. Name three different units of WCF

Window Communication Foundation has three prime components

  • Assistance/Service group
  • Host
  • Endpoint
  1. Who is a client?

Client in a WCF is a link of communication between between applications. WCF obey “Software and Service Model” here, all important components are defined as services and the services are used by client program. 

  1. WCF is known for the security it offers. Can you name a few security features offered by WCF?

WCF provides four supreme security features. They are:-

  • Strong Authentication 
  • Complete Confidentiality 
  • Secured Authorization
  • Integrity
  1. What are the benefits of using Service Oriented Architecture?

SOA or Service Oriented Architecture is the principle behind the structure and working of Windows Communication Services. Every component or unit in an SOA is a service.

The benefits of using Service Oriented Architecture or SOA are:-

  • The services are loosely-coupled to allow fixing and culturing other units without hampering the working of one module.
  • All the services are independent of each other
  • Maintaining an SOA module is not very difficult or time taking.
  • Interoperability to work in different languages without a hassle
  • Location and workplace are never an issue when working with SOA
  • Capacity to provide services on varied scales.
  1. Why is the WCF framework efficient than its other counterparts?

WCF framework provides a free environment to build communicative applications. A WCF interface can be considered easy and feasible to use in many ways. Security is never comprised in the WCF framework. The WCF is compatible with various existing .NET technologies like MSMQ, WSE, ASMX, and other web services. 

Interoperability is yet another advantage the WCF framework has over other methodologies. Medium level changes in the module are never troublesome as they are loosely bound and allow correction without disturbing the algorithm of other units/modules.

Interaction is very active while working with WCF for business development. MSMQ services in WCF allow partners to send and receive messages in real-time and share other important data.

  1. Why are AJAX and REST support important in the WCF framework?

AJAX and REST support the WCF interface and unlock many more possibilities to outperform other interfaces.WCF interface allows and provides plain XML data. The best part being the plain XML data’s information is never encoded in SOAP. Whereas REST is a web technology, specifically advanced with web 2.0 technology. WCF supports formats other than XML too, the first example is ATOM. Non-XML formats are also subjected to WCF.

  1. Explain the types of contracts available in the WCF interface.

Contracts define the structure of the WCF interface. The contract contains clear elements that refine the service. It allows the client to choose an action for the service required. The contract contains information about WCF services since they are a part of WCF endpoints.

The contracts available in the WCF interface are:-

  • Service Contract: defines the interface of the service initiated
  • Operation Contract: deliberates the link between client and server
  • Data Contract: This illustrates the data required to exchange. This also conveys an agreement between the client and service describing the service to be exchanged. 
  • Message Contract: This enables interaction between services and allows communication between SOAP headers. 
  1. Name different types of binding available in the WCF interface.

Binding helps in better communication and ensures proper protocol to handle a client and their needs. Binding is a wholesome path to harness proper endpoint communication. It helps the system to exchange, transport, and encode. These binding element helps maintain a secure network to allow a security mechanism to catch details without trouble. 

Different types of binding available in the WCF interface are:-

  • NetTCP Binding
  • MSMQ integration Binding 
  • NetPeerTcp Binding
  • BasicHTTP binding
  • NetNamedPipe Binding
  • WSFederationHttp Binding
  • WSDualHttp Binding
  1. Explain service proxy in WCF.

Service proxy in WCF is important for managing proxy life-cycle and helps in communication with the client and their server. It is a CLR class proxy that exposes the connection to initiate communication. Here, the communication takes place through requests and responses.

  1. Describe the different modes of communication in the WCF.

There are three ways of communication in the WCF.

  • Request/Response: This is a default program for message exchange. Here, the client sends a message to the server to receive a response
  • One Way: useful to receive messages, but replies are never guaranteed. Also called ‘fire and acknowledge’ one-way communication redirects the client that their message has been looked on to, but the response is never awaited
  • Duplex: helps generate an independent exchange of messages between client and server. Duplex or two-way communication in the WCF is useful when discussing issues and clients events.  
  1. Define data contract in the WCF

A data contract is a simple formal agreement between client and service. It structures the external format of the service. A data contract is necessary for shaping the records and defining the data that needs to be exchanged. It contains all necessary data to refine the service operation. Data contract lists out the type of data required to be exchanged. The two most important components of data contract are serialization and deserialization. 

Serializations contribute to exchanging data that can be easily transmitted through the network, whereas in deserialization the sequence is allowed to shape itself back into the object. Changes are an inevitable part of the data contract. 

  1. What is SOA?

SOA or Service Oriented Architecture is a style of operation. SOA uses communication steps to build an application without a mess. SOA helps to connect to networks faster. Services and their results are the main fundamentals in an SOA architectural style. SOA is linked with API or Application Programming Interface, this enables smooth maintenance. An important point that needs to be acknowledged is, Web services and SOA are different but the latter is used predominantly to achieve necessary standards.

  1.  Explain the difference between classic web services (ASMX) and WCF.

ASMX: uses SOAP (Simple Object Access Protocol) to send and receive messages. Here, language and platform are not a barrier. ASMX can construct web services that require no knowledge about languages or platforms but allow registering messages through the SOAP interface.

WCF: open-source foundation using .NET interface. WCF uses endpoints, service class, and hosting environment as its main component. Creating communication channels is easy through MSMQ, Remoting, etc. The primary idea behind creating a Window Communication Foundation is to ease interprocess communication. Communication service in WCF can be transported to any protocol. 

  1. What are the endpoints in the WCF?

The endpoint in WCF is a combination of ABC i.e. Address, Binding, and Contract. Endpoints help to fix communication channels between application and service. 

Address: defines the location of the service. The address is circumscribed at the property level.

Binding: is a part of the endpoint. Binding is defined as a service-level property. It decides the protocol, encodings, and transport factor. Binding is also used to revive all the factors that parties have decided to communicate on.

Contract: is a property of endpoint used primarily for communication. It is an interface helping client and server communicate efficiently over the operation. 

  1. Name the types of contracts available in WCF.

There are in total 4 different types of contracts available in WCF.

  • Data Contracts
  • Service Contracts
  • Message Contracts
  • Fault Contracts


Windows Communication Foundation is a .NET framework. WCF is mainly used in building service-oriented applications. The biggest deal here is, WCF is an open-source interface. WCF interface requires highly qualified individuals to cater needs of clients. Therefore, interviews tend to be an important aspect before selecting the right employee. The field requires intensive knowledge about every module. You can expect questions regarding WCF therefore, brush your concepts, and all the very best for your interview.

Frequently asked question

  1. Will the interviewer ask questions related to the .NET framework?

Yes, the .NET framework is a part of the WCF interface therefore you can expect questions underlining .NET

  1. Are Indigo and WCF the same?

Previously, WCF was known as Indigo. Yes, they are the same.

  1. What is interoperability in WCF?

Interoperability is the primary function of the WCF. This allows applications to run not just on Windows OS but any platform. WCF is an open-source interface by Microsoft that readily allows compatibility with other operating systems.

WCF Interview Questions And Answers

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