Top 30 WCF Interview Questions & Answers For Freshers & Experienced

Introduction

In this blog post for WCF interview questions and answers, we will share a complete list of frequently asked questions that could help you in cracking your next interview and get the dream job right away. You would be able to answer these questions if you have a basic understanding of the technology or worked on the technology before.

These questions are usually asked by big MNCs including Accenture, Snaphunt, HCL, Infosys, and more in a computer programming interview. So, let us move ahead and make your journey interesting with a quick list of questions and answers prepared after deep research only.

Why is Studying WCF Interview Questions Required?

A lot of companies use Windows Communication Foundation (KCF) routinely, like in computer programming, .NET Developer, application programmers, backend architects, etc. So, having a command over KFC and answering questions with confidence will put you in the top seat, and represent you as a well-prepared candidate.

WCF Interview Questions

1. Explain your understanding of the WCF technology.
2. Explain the WCF fundamentals and its architecture in brief.
3. What is the need for WCF services for your business?
4. What are the benefits or advantages of WCF Technology?
5. How will you distinguish the WCF from other web services?
6. What do you mean by SOA? Do web services come under SOA?
7. How will you define the service contract in WCF?
8. What do you mean by contract in WCF? Explain the type of contracts too?
9. How will you explain the data contract in WCF?
10. How will you define the message contract in WCF?
11. What are the endpoints in WCF? Explain its common types too?
12. What is the need for Address when defining service endpoints in WCF?
13. What is binding in WCF? Explain its characteristics too?
14. What are the transactions in WCF? Explain its types too? 
15. What are the hosting requirements for a web service?
16. What is the difference between ASP.NET Web Services and WCF

WCF Interview Questions with Answers for Fresher

Q1). Explain your understanding of the WCF technology.

Ans:- WCF is a platform for building distributed apps or services among multiple endpoints in Windows. The initial name for WCF was Indigo and it was designed for building service-oriented apps and offers interoperability too.

The WCF is abbreviated as Windows Communication Foundation; this is a popular programming model that is suitable for designing service-oriented apps. It can be used to create or deploy services that are easily accessible by multiple clients worldwide.

It provides an environment where a particular service is accessible by Windows or Linux clients both. The features of WCF are just endless when compared to any other web service. WCF technology has been proposed by Microsoft and it could be accessed through multiple protocols like HTTP, TCP, MSMQ, and more.

Q2). Explain the WCF fundamentals and its architecture in brief.

Ans:-The framework is suitable for sending asynchronous messages from one endpoint to another endpoint. The framework is using a set of APIs to exchange messages between the server and the client. It helps in accessing apps over the internet whether it is hosted on the same server or a different server.

Read: What is Microsoft .Net Framework? Complete Architecture Tutorial Guide

WCF Fundamentals

• Interoperability
• Unification
• Service Orientation

WCF Architecture

The WCF architecture is made up of the following layers – Application Layer, Contracts, Service Runtime, Messaging, Activating, and Hosting.

Q3). What is the need for WCF services for your business?

Ans:-

• It is used to exchange messages in XML format with the help of HTTP protocol to maintain interoperability.
• WCF uses remote services to exchange messages in binary format with the help of TCP protocol to maintain performance.
• A service to exchange data securely over the network in real-time.

Q4). What are the benefits or advantages of WCF Technology? 

Ans:-

• The framework can be configured to work independently with SOAP or RSS.
• This a popular communication technology that offers remarkable performance when compared to other Microsoft specifications.
• This framework is suitable for secure communication, data transmission, and even speed can be optimized. It is exchanging data in binary format to decrease the latency.
• This is a distributed management system that is applicable to almost all applications that are developed with WCF.

Q5). How will you distinguish the WCF from other web services?

Ans:-

Features	Web Services	WCF
Hosting	They can be hosted in IIS only.	It can be hosted in IIS, windows service, self-hosting, and more.
Programming	Here, you need to add a attribute to the class.	Here, you should add a attribute to the class.
Operations	The duplex operation is not supported in the case of web services.	The duplex option can be supported freely in the case of WCF.
Protocol	Data can be exchanged using the HTTP protocol only.	Data can be exchanged with HTTP. TCP, MSMQ, and more.
Encoding	XML and Custom Encoding	XML, Custom, Binary, MTOM
Services	Security	Secure, reliable messaging, transactions, etc.

Q6). What do you mean by SOA? Do web services come under SOA?

Ans:-

SOA means a service-oriented architecture that helps to organize apps as Services. This is a group of methods that define the business logic and helps to connect with DB and other services quickly. Take an example of the restaurant where you go and order food. Your order will go from the counter to the kitchen and it is served on your table finally.

The benefits of SOA architecture - Independent, Self-contained, self-explanatory, etc. SOA Architecture – It consists of four key abstractions – an application front end, a service repository, a service bus, a service, etc. Web services are not SOA but preferable standards to achieve the SOA.

Q7). How will you define the service contract in WCF?

Ans:-

The Service Contract is a collective mechanism where the capabilities and requirements of service are specified for its consumers. It will explain the list of operations that will be performed by the service when it is executed. It will define the data types, protocols, and operation locations for the service. Defining a service contract for WCF is not easy but developers should have the right skills and experience to complete this task.

Read: C# Interview Questions and Answers

WCF Interview Questions and Answers For 5 Years Experience

Q8). What do you mean by contract in WCF? Explain the type of contracts too.

Ans:- The main objective of defining contracts is to make agree with both client and server for the same operations, structures, data types, etc. This is important to establish secure communication between the two. This is a formal agreement to define the platform neutrality and standards as well as what is done by the services. Here is given most common types of contracts that are frequently used within WCF technology.

• Service Contract
• Operation Contract
• Data Contract
• Message Contract
• Fault Contract

Q9). How will you explain the data contract in WCF?

Ans:- A data contract is a formal agreement between the server and the client between whom data is exchanged securely. It could be defined either implicitly or explicitly based on the requirement. It will define the format, structure, and type of data to be exchanged between parties. It will define the process of how can data be serialized or deserialized. This is a versioning system that helps to manage changes for structural data. [code] [DataContract] Public class cuboidInfo { } [/code] Here, in the example, we have given the general syntax for the data contract. It will provide complete data abstraction at a new level like never before.

Q10). How will you define the message contract in WCF?

Ans:-The objective of the message contract in WCF is to define the structure for the message and how can you perform the serialization. By default, it will take care of SOAP messages based on service requirements. Here is given the general syntax for message contract in compact form –   [code] [MessageContract] Public Class AutherRequest { Public String AutherId; } [/code]    

Read - https://www.janbasktraining.com/blog/technical-interview-preparation/

Q11). What are the endpoints in WCF? Explain its common types too.

Ans:-Endpoints are responsible to provide the necessary configuration and help1101 in creating the complete WCF application too. It will define the complete piece of information on how can you exchange the data between two points. It consists of three major parts – address, binding, and Contract. The basic structure of endpoints in WCF is shown below in the diagram –

• An address uniquely identifies each endpoint.
• The binding will specify how clients can communicate with endpoints.
• The contract will identify the list of available operations.

All communications in WCF have to pass through service endpoints so that data can be exchanged securely as needed by enterprises.

Q12). What is the need for Addresses when defining service endpoints in WCF?

Ans:-If you are not sure where to send messages then addresses play an important role here. This is a Uniform Resource Locator (URI) that will identify the location of the receiver. It is similar to the network address and highly useful to send or receive messages. It can be divided into four parts – Scheme, Machine, Port, and path. Each address is unique in itself and finds out the location of the receiver accurately without any error. There are plenty of protocols are used to exchange messages in WCF. These are HTTP, TCP, MSMQ, etc.

Read: Microsoft Azure Interview Questions and Answers for Experienced Developer

Q13). What is binding in WCF? Explain its characteristics too.

Ans:-The Binding will explain to you how will you communicate with the service. There are plenty of protocols to facilitate communication in WCF. These are HTTP, TCP, MSMQ, etc. The characteristics of binding are Protocol, Encoding, or Transport, etc.

Q14). What are the transactions in WCF? Explain its types too.

Ans:-A transaction is a logical unit that defines multiple activities in WCF either pass or fails. The two common types of transactions are – Atomic and Long Running. Two phases of transactions are Prepare Phase and the Commit Phase.

Q15). What are the hosting requirements for a web service?

Ans:-The hosting requirements for a web service include – Availability, Reliability, Manageability, Versioning, Deployment, State, etc.

WCF Interview Questions and Answers for Experienced in .Net

Q16).   What are default Endpoints?

Ans:- WCF offers some default endpoints to the service if a service host doesn’t define any endpoints but has at least one base address. For example, WCF uses the basic binding for the HTTP address. This is an important answer to these kinds of wcf interview questions.

Must Read : How To Prepare For A Technical Interview

Q17).  What are standard Endpoints?

Ans:- WCF provides a set of pre-defined endpoints known as Standard Endpoints for metadata exchange, discovery, and web. You can configure the standard endpoints by using a config file and programmatically. Here is the list of standard endpoints :

• MEX endpoint
• webHttpEndpoint
• webScriptEndpoint
• workflowControlEndpoint
• announcement endpoints
• discoveryEndpoint
• udpAnnouncementEndpoint
• udpDiscoveryEndpoint

This is an important answer to these kinds of wcf interview questions.

Q18).  What are the different WCF contracts?

Ans:- WCF contract specifies the service and its operations. WCF has five types of contracts:

• Service contract
• Operation contract
• Data contract
• Message contract
• Fault contract.

This is an important answer to these kinds of wcf interview questions.

Q19).  What are the various ways of hosting a WCF service?

Ans:- There are four ways of hosting a WCF service.

• Self-Hosting
• Windows services hosting
• IIS hosting
• Windows Activation Services hosting (WAS)

Q20). What is Binding?

Ans:- WCF binding specifies how the service and client will communicate with each other in terms of transport protocols and encoding (such as text or binary). WCF binding is a set of binding elements and each element specify, how the service and client will communicate with each other. Each binding must have at least one transport element and one message encoding element. This is an important answer to these kinds of wcf interview questions.

Q21).   What are the different types of bindings in WCF?

Ans:- WCF supports the following types of built-in bindings:

• Basic binding
• Web binding
• Web Service (WS) binding
• WS Dual binding
• TCP binding
• IPC binding
• MSMQ binding
• Federated WS binding
• Peer Network binding
• MSMQ integration binding

Q22).  What are the ways to create a WCF Client?

Ans:- There are two ways to create a WCF Client or calling a WCF Service as:

• WCF Proxy
• Channel factory

Q23). What is Instance Management in WCF?

Ans:-WCF manages the session by creating the instance of the service class. This created instance(s) to handle the incoming service request. In WCF, the session is the way of managing the services instance(s) so that the server can use these instances in an optimized way. At the server-side, the InstanceContext class is used to manage service class instances. There are following instance management ways :

• Per Call
• Per Session
• Single

This is an important answer to these kinds of wcf interview questions.

Q24)  What is Concurrency Management in WCF?

Ans:- Concurrency management is closely related to the Instance management in WCF but both are two different things. Instance management specifies how the service instances are created while Concurrency management specifies how many concurrent requests are handled by the service instances. By using concurrency, you can make your service instance thread-safe. By default, a per-call service instance is thread-safe since each request is served by a new service instance. A per-session service instance is not thread-safe since multiple requests of a client are served by a single service instance. Hence, it’s required concurrency management. A single service instance is not thread-safe since multiple requests of all clients are served by a single service instance. Hence, it’s required concurrency management. 

Q25). What is Impersonation?

Ans:- Impersonation is a way to authorize a caller (client) identity to access the service domain’s resources. The service resources may be local files or database tables and should be on the same machine on which service is hosted. By default, impersonation is disabled and resources are accessed by using the WCF service's process identity.

Q26).  What is service versioning?

Ans:- After the initial deployment of the WCF service, you may need to change the service for a variety of reasons like as changing business needs or fixing others issues. Each change in your existing service introduces a new version of the service. Service versioning is helpful in backward compatibility with your existing clients. 

Q27) What is WCF Data Service?

Ans:- WCF Data Services uses OData (Open Data Protocol) protocol for querying or manipulating the data. WCF Data Services is built on top of WCF REST Services. It is a RESTful service to support CRUD operations on the database using the HTTP protocol. It supports all database operations using URI. DATA protocol can expose data from the relational database, File systems, Web sites, services etc. It supports XML or JSON format for exposing the data. 

Must Read : Microsoft Net Framework

Q28).  What is SOA?

Ans:- SOA stands for Service Oriented Architecture. It is an architectural design pattern which states that every component of a system should be a service (here service means a unit of a program that serves a business process), and the system should be composed of several loosely-coupled services means services should be independent of each other, so that changing one of them should not affect any other services.

Q29). What is the difference between ASP.NET Web Services and WCF

Ans:- 

WCF	ASP.NET Web Services
To define WCF services service contract and operation contract attributes are used	To define ASP.NET Web services, webmethod attributes are used
This is hosted in IIS, WAS, Window service,	Hosted only in IIS
Support protocols like TCP,HTTP,HTTPS,MSMQ	Supports only HTTP, HTTPS
Supports data contract	Supports XML serializer

Conclusion

WCF is still a framework that allows you to design extremely sophisticated solutions and manage all parts of your data flow, and it remains a necessary skill for any senior.NET developer. If you're preparing for a WCF interview, these questions and answers will help you ace the interview and get the job. WCF is a powerful framework for developing web services, and these questions will test your knowledge of the core concepts. Be sure to brush up on your WCF before the interview, so you can impress your interviewer and land the job. Thanks for reading!

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