Profiling gathers information about an executing application, allowing you to determine those improvements that are required in your application.
Ten reasons why you should bother profiling your .NET code
1) Focus on portions of your .NET code that really require attention
2) Identify code blocks with performance issues
3) Compare alternative approaches
4) Get accurate code execution response times
5) Avoid guessing performance issues
6) Visualize performance and memory usage
7) Track the lifecycle of your .NET objects
8) Avoid unnecessary loading or initialization of your program
9) Optimize your looping constructs in .NET
10) Identify memory leaks in your application

How to profile your .NET code?

• CLR Profiler
• Using PerfMon