Basically you need to clear all concepts on object orientation. it includes all features like inheritance, polymorphism, encapsulations, recursion, classes, methods, abstractions etc.
prepare for some .NET techniques like Threading, assemblies, use of garbage collector, use of GAC.
use of .NET basic controls like dropdwonlist, gridview, textbox, button. some AJAXtoolkit controls like update panel, auto complete extender. some database concept like storedprocedure, cursors, triggers. ado.net concept like dataset, datareader, dataadapter
prepare on windows based as well as webbased technologies
Editor, DotNetSpider MVM
Microsoft MVP 2014 [ASP.NET/IIS]