Key Value pair in C#.net

Question

I want the source code in c# .net regarding with key value pair in such a way that If the client enters the Key of string data type & output should be printed as an Integer value consisting of 8 numbers ie integer data type as chosen in such a way that these Key & Value are in the text file (.txt) in which it should read the key in the text file & should print the appropriate integer value as entered in the text file as the output.

I want the solution for this as soon as possible in c# 4.0 framework or Visual Studio 2010 coding design.