Eager to know Differences between .NET 4.0 and .NET 4.5 in High level in .NET and also differences in ASP.NET, C# also in these frameworks
What is new in .NET Framework 4.5 & What's new and expected in .NET Framework 4.5:
differences in ASP.NET in these frameworks
Compare What's New in ASP.NET 4 and Visual Web Developer and What's New in ASP.NET 4.5 and Visual Studio 11 Beta:
Asp.net 4.0
Web.config
File Refactoring And for Asp.net 4.5 there is also a long list of improvements:
HttpRequest
handling differences in C# also in these frameworks
Go Through C# 4.0 - New C# Features in the .NET Framework and What's New for Visual C# in Visual Studio 11 Beta.
Edit:
The languages documentation for C# and VB breaking changes:
VB: Visual Basic Breaking Changes in Visual Studio 2012
C#: Visual C# Breaking Changes in Visual Studio 2012
Hope this help you get what are you looking for..