.NET equivalent of the old vb left(string, length) function

Question

As a non-.NET programmer I\'m looking for the .NET equivalent of the old Visual Basic function left(string, length). It was lazy in that it worked for any lengt

Answer 1

Add a reference to the Microsoft.VisualBasic library and you can use the Strings.Left which is exactly the same method.

Answer 2

Another one line option would be something like the following:

myString.Substring(0, Math.Min(length, myString.Length))

Where myString is the string you are trying to work with.

Answer 3

Here's an extension method that will do the job.

<System.Runtime.CompilerServices.Extension()> _
Public Function Left(ByVal str As String, ByVal length As Integer) As String
    Return str.Substring(0, Math.Min(str.Length, length))
End Function

This means you can use it just like the old VB Left function (i.e. Left("foobar", 3) ) or using the newer VB.NET syntax, i.e.

Dim foo = "f".Left(3) ' foo = "f"
Dim bar = "bar123".Left(3) ' bar = "bar"

Answer 4

Another technique is to extend the string object by adding a Left() method.

Here is the source article on this technique:

http://msdn.microsoft.com/en-us/library/bb384936.aspx

Here is my implementation (in VB):

Module StringExtensions

    <Extension()>
    Public Function Left(ByVal aString As String, Length As Integer)
        Return aString.Substring(0, Math.Min(aString.Length, Length))
    End Function

End Module

Then put this at the top of any file in which you want to use the extension:

Imports MyProjectName.StringExtensions

Use it like this:

MyVar = MyString.Left(30)

Answer 5

You can either wrap the call to substring in a new function that tests the length of it as suggested in other answers (the right way) or use the Microsoft.VisualBasic namespace and use left directly (generally considered the wrong way!)