Difference between SOAP and REST Web Services (from generic to .NET)

	SOAP	REST
Acronyme	Simple Object Access Protocol	REpresentational State Transfer
Architecture	SOA based architecture that use middleware interoperability.	Architecture style protocol designed for web based communication assuming only point to point communication.
Message Format	XML inside a SOAP Envelope	XML
In business logic	Uses services interfaces to expose the business logic.	Uses URI to expose business logic.
Standards	Defines standards to be strictly followed.	Does not define too much standards like SOAP.
Communication	Use WSDL for communication between consumer and provider.	Uses XML or JSON to send and receive data.
Transport	Transfer is over HTTP, Also uses other protocols such as SMTP, FTP, MIME, JMS, HHTP, etc.	Transfer is over HTTP only.
JavaScript calls	JavaScript can call SOPA but it is difficult to implement.	Easy to call from Javascript.
Security	SOAP defines its own security.	RESTful web services inherits security measures from the underlying transport.
Payload	Payload must support SOAP schema.	Payload can be of any format.
Error Handling	Doesn't support error handling.	Has built-in error handling.
External Calls	Invokes services by calling RPC method.	Simply calls services via URL path.

What do I choose, SOAP or REST?

It depends!!

Both protocols have their advantages and disadvantages, but you should choose which protocol you are using based on the requirements of the problem. Instructing you on how to accomplish that is beyond the scope of this question and answer.

And in  .NET world, you can find more details to choose  :

https://msdn.microsoft.com/en-us/magazine/dd942839.aspx

https://msdn.microsoft.com/en-us/magazine/dd315413.aspx

And REST is more popular from ASP.NET WEB API.

http://www.asp.net/web-api/overview/older-versions/build-restful-apis-with-aspnet-web-api

And the use of SOAP is here from WebServices :
https://msdn.microsoft.com/en-us/library/ms972326.aspx
http://www.codeproject.com/Articles/1231/ASP-NET-Web-Service
https://msdn.microsoft.com/en-us/library/t745kdsh.aspx

We will add a sample next post using REST ASP.NET WEB API 2.0