how can i give vesion to my C#.net window application ??

If you right-click on your project in Visual Studio and choose Properties, and then click the Assembly Information... button on the Application tab, you can enter an assembly version and a file version.

The assembly version is used by .Net to distinguish between different versions of the same assembly. The file version is what you see when you right-click a file and look at it's properties; the file version is really just for display and doesn't have much significance to anything.

I usually make the two the same on my applications.

If you want any of the numbers to automatically increment with each build then you can set the value to "*". That way you don;t have to manually change the version number for each build.