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I have a asp.net 4.5 webforms app with a SQL Server 2014 backend<br />
<br />
Customer(s) wants to access his data via an API<br />
We currently don't have an API so need to create one<br />
<br />
The web app uses 3 tier's:<br />
1 Web <br />
2 Business Logic<br />
3 Data Access Layer<br />
<br />
<br />
Would I use the business logic layer for the API or just deal direct with DB?<br />
Can someone give me an idiots guide on how to get started using .net, and rough outline of architecture <br />
I also have no idea about securing it?<br />
Any advice appreciated on how to get started speccing it out
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I have a asp.net 4.5 webforms app with a SQL Server 2014 backend

Customer(s) wants to access his data via an API
We currently don't have an API so need to create one

The web app uses 3 tier's:
1 Web 
2 Business Logic
3 Data Access Layer


Would I use the business logic layer for the API or just deal direct with DB?
Can someone give me an idiots guide on how to get started using .net, and rough outline of architecture 
I also have no idea about securing it?
Any advice appreciated on how to get started speccing it out

Existing Web App - create an API for customers - how?

The successor to Active Server Pages, ASP.NET websites utilize the .NET framework to produce dynamic, data and content-driven web applications and services. ASP.NET code can be written using any .NET supported language. As of 2009, ASP.NET can also apply the Model-View-Controller (MVC) pattern to web applications

ASP.NET

C# is an object-oriented programming language created in conjunction with Microsoft’s .NET framework. Compilation is usually done into the Microsoft Intermediate Language (MSIL), which is then JIT-compiled to native code (and cached) during execution in the Common Language Runtime (CLR).

A Web service is a method of communication between two electronic devices over a network. It is a software function provided at a network address over the Web with the service always on as in the concept of utility computing. A web service has an interface described in Web Services Description Language (WSDL). Other systems interact with the Web service in a manner prescribed by its description using SOAP (Simple Object Access Protocol) messages. There are two major classes of Web services: REST-compliant web services, and Arbitrary web services.