Create and use an extension in vb.net

Question

I've got 2 parts to this question:

1. How to get extension to work in vb.net
2. How to call the lambda expression in vb.net

I want to implement an extension in VB.NET and while I've used them numerous times in C#; I can't see why this won't work for me.

Here is one of extension I need to call in C#

public static class EnumerableExtensions
{
    public static string ToSeparator<T, TU>(this IEnumerable<T> source, 
    Func<T, TU> func, string separator, bool endWithSeparator)
    {
        string separatedString = string.Join(separator, source.Select(x =>
        {
            var value = func(x);
            return value == null ? string.Empty : value.ToString();
        }));

        separatedString += (endWithSeparator ? separator : string.Empty);

        return separatedString;
    }
}

I've converted to vb.net (using DeveloperFusion), so I'm not sure how accurate this is first of all as I had to make a few changes manually:

Imports System.Linq
Imports System.Runtime.CompilerServices

Namespace [Shared].Extensions

  Module IEnumerableExtensions

    <Extension()> _
    Public Function ToSeparator(Of T, TU)(source As IEnumerable(Of T), 
    func As Func(Of T, TU), separator As String, endWithSeparator As Boolean) 
    As String

      Dim separatedString As String = String.Join(separator, source.Select(
      Function(x)
        Return If(x Is Nothing, String.Empty, x.ToString())
      End Function))

      separatedString += (If(endWithSeparator, separator, String.Empty))

      Return separatedString

    End Function

  End Module

End Namespace

This is created in a separate assembly in C# and it works just fine when calling this way:

var list = mylist.ToSeparator(m=>m.LastName, ",", false);

but in vb.net, it just will not show up in intellisense,

2) I'm not sure how to call the part of the function m=>m.Lastname in vb.net

Unfortunately, my share library is also written in vb.net so I cannot justify creating a separate assembly in c# to for these few extensions I need, so I really need this resolved in VB.NET

Am I doing anything wrong? Any ideas why it won't show up in intellisense in vb.net the way it does in c#?

I'm using .NET 4.0 and VS 2013.

Thanks.

UPDATE

Below is the updated extension that's correctly converted to VB.NET. I thought I'd update it as it might be useful to someone else.

<Extension()> _
Public Function ToSeparator(Of T, TU)(source As IEnumerable(Of T), 
func As Func(Of T, TU), separator As String, endWithSeparator As Boolean) As String

  Dim separatedString As String = String.Join(separator, source.[Select](
    Function(x)
      Dim value As TU = func(x)
      Return If(value Is Nothing, String.Empty, value.ToString())
    End Function))

  separatedString += (If(endWithSeparator, separator, String.Empty))

  Return separatedString

End Function

Using this with @DStanley's answer will work as expected.

Answer 1

1)in vb.net, it just will not show up in intellisense,

You probably just need to make your Module public. VB Modules are Friend by default (roughly equivalent to C#'s internal :

Public Module IEnumerableExtensions

2) I'm not sure how to call the part of the function m=>m.Lastname in vb.net

A quick search for "VB Lambda" would have yielded plenty of examples:

list = mylist.ToSeparator(Function(m) m.LastName, ",", False)