[c#] How do I get the current username in .NET using C#?

I totally second the other answers, but I would like to highlight one more method which says

String UserName = Request.LogonUserIdentity.Name;

The above method returned me the username in the format: DomainName\UserName. For example, EUROPE\UserName

Which is different from:

String UserName = Environment.UserName;

Which displayed in the format: UserName

And finally:

String UserName = System.Security.Principal.WindowsIdentity.GetCurrent().Name;

which gave: NT AUTHORITY\IUSR (while running the application on IIS server) and DomainName\UserName (while running the application on a local server).