String to Enum

The following extension converts a string value to a member of a specific member of an Enum unless the string value is not a member of the Enum. I intentionally did not replicate TryParse in Framework 4 and case of member must match that of a member in the Enum passed.

I am interested if anyone can see room for improvement

Usage

Code:

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    Public Enum UserType
        None
        Administrator
        Manager
        Developer
        Consultant
    End Enum
    Private Sub Demo()
        Dim UserType As String = "Developer"
        Dim UserName As String = "Kevin Gallagher"
        Try
            Dim UserPositionType As UserType = UserType.ToEnum(Of UserType)()
            Console.WriteLine("{0} is a {1}", UserName, UserPositionType)
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Sub

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Extension

Code:

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    ''' <summary>
    ''' Converts string value to a member of an Enum
    ''' </summary>
    ''' <typeparam name="T"></typeparam>
    ''' <param name="sender"></param>
    ''' <returns></returns>
    ''' <remarks>
    ''' An exception is thrown if member is not in Enum members
    ''' </remarks>
    <System.Diagnostics.DebuggerStepThrough()> _
    <System.Runtime.CompilerServices.Extension()> _
    Public Function ToEnum(Of T)(ByVal sender As String) As T

        Dim TheType As Type = GetType(T)

        If [Enum].IsDefined(GetType(T), sender) Then
            Return CType(System.Enum.Parse(TheType, sender, True), T)
        Else
            Dim BaseType As String = TheType.ToString
            Dim Pos As Integer = BaseType.IndexOf("+")
            Dim ErrorMsg As String = ""
            If Pos > -1 Then
                Dim EnumName As String = BaseType.Substring(Pos + 1)
                ErrorMsg = String.Format("'{0}' not a member of '{1}'", sender, EnumName)
            Else
                ErrorMsg = String.Format("{0} not a member of {1}", sender, TheType)
            End If
            Throw New Exception(ErrorMsg)
        End If

    End Function

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