ASP.NET is a part of Microsoft’s .NET framework and is considered Microsoft’s premier server side programming language. 
There are two approaches to program websites using ASP.NET: Web Forms approach and the MVC approach. Web forms approach is the older approach and is suited more to the programmers who are switching from Windows Form applications to web applications, while MVC is more suited to web developers who follow patterns and like to program in component oriented way. This article contains some of the most useful resources for learning ASP.NET.
The best way to learn a technology is to look resources on its official website or forum. Asp.net is ASP.NET’s official forum and contains hundreds of resources that help beginners as well as professionals learn ASP.NET in a very easy manner.

There is hardly a web developer who hasn’t take help from w3schools.com in his life. The website contains articles that teach ASP.NET from scratch and also touches advanced concepts. This source is highly recommended to those who are just starting their career in ASP.NET.