AddIfDoesntExist

''' <summary>
''' Adds an object to the list only if it does not already exist in the list.
''' </summary>
''' <param name="ls"></param>
''' <param name="value"></param>
''' <returns></returns>
''' <remarks></remarks>
<Extension()> _
Public Function AddIfDoesntExist(Of T)(ByVal ls As List(Of T), ByVal value As T) As List(Of T)
    If ls.Contains(value) = False Then
        ls.Add(value)
    End If

    Return ls
End Function

Dim ls As New List(Of String)

ls.AddIfDoesntExist("Blake")
ls.AddIfDoesntExist("Blake")
ls.AddIfDoesntExist("Bob")
ls.AddIfDoesntExist("William")
ls.AddIfDoesntExist("Jacob")