Info You can have more parameters on an extension method. The first one is always the instance the method is called upon.
Important The System.Runtime.CompilerServices namespace must be imported. This provides access to the Extension attribute.
' Test extension on a string.
Dim v As String = "ABC"
' Test nothing value.
v = Nothing
' Test empty string.
v = ""
Public Function LastChar(ByVal value As String) As Char
' If string is not nothing, and has at least one char,
' ... return last char.
' Otherwise return a question mark.
If Not value = Nothing Then
If value.Length >= 1 Then
Return value(value.Length - 1)
Discussion. When should you use extension methods in VB.NET programs? If a small and useful method is used often, it may be helpful to turn it into an extension method.
And I often use extension methods to test characters and strings. For example, I use a "IsUpperOrDigit" extension method.
Info No such method exists in the .NET Framework, but the implementation is obvious.
Warning I usually end up with too many extension methods. It is preferable to limit the number, and have strict requirements.
Summary. An extension method changes the syntax for calling a method. It makes a non-Class method look like a Class method. This sometimes can yield simpler programs that are easier to read.