C# - Remove A Trailing Part Of String In .NET?

For removing trailing part is I use the code

str.substring(0,str.length -2)

Is there a better way? I especially dislike using str.length.

Edit I wanted the question to be as short and simple as possible and I supposed that I just overlooked some String method. I try to be more precise.

I need to remove given number of characters from the end of a string. I don't want to care what the characters are and I don't want to introduce a risk of removing more characters.

If the number is larger then string length let's there is an exception (the string should be validated earlier).

I don't have the problem especially with length, but with referencing a variable twice (imagine a function instead of a variable). I also don't like necessity of subtraction but it is only a personal preference.

The question is taged vb.net so there is vb.net code (should be in a module):

<System.Runtime.CompilerServices.Extension> _
Public Shared Function RemoveFromEnd(stringValue As String, removedCharacters As Integer) As String
Return stringValue.Substring(0, stringValue.Length - removedCharacters)
End Function