Can any one guide me to learn LINQ in C#.net i am new to this concept
The videos at http://www.asp.net/learn/ are great. They have an entire section on Linq that will take you from "new solution" to fully working examples.
LINQ is a pretty big subject.
I would start with Hooked On LINQ
The way I learned Linq was from the book Linq in Action
Get LinqPad!
Its a great way to learn LINQ, supports LINQ to SQL, LINQ to Objects and LINQ to XML, and it comes preloaded with 200+ examples from the book C# 3.0 in a Nutshell.
I'm a long-time SQL developer, and I found that all I needed for the transition to learning LINQ was 101 LINQ Samples off of msdn. All the basics are there, if you understand the generalities of a query-based syntax already. I don't know what your existing expertise is, so thought I'd throw that out there.