Problem Creating A Function From An Assembly

I have compiled a dll with the following code:

Imports System
Imports System.Data
Imports System.Data.SqlClient
Imports Microsoft.SqlServer.Server
Imports System.Data.SqlTypes

Public Class SICTrans

Public Shared Function TransSIC(ByVal inpSIC As String) As String
'Dim conn As SqlConnection = New SqlConnection("context connection=true")
Dim NewSIC, TempSIC, tempFSIC As String

If Len(NZ(inpSIC)) > 0 Then
TempSIC = NZ(inpSIC)

If Len(TempSIC) < 5 Then TempSIC = Left("00000", 5 - Len(TempSIC))

tempFSIC = Left(TempSIC, 2) + "." + Mid(TempSIC, 3, 2)

If Val(Right(TempSIC, 1)) > 0 Then

tempFSIC = tempFSIC + "/" + Right(TempSIC, 1)
End If
End If

NewSIC = tempFSIC

TransSIC = NewSIC

End Function
Public Shared Function NZ(ByVal input As String) As String
If Not (input Is Nothing) Then
Return input
Exit Function
End If
Return String.Empty

End Function
End Class

Which compiles fine...

i then use the following code to create the assembly in SQL which is fine:

USE NARD
GO
CREATE ASSEMBLY SICCodeTrans
FROM 'c:SICCodeTrans.dll'
WITH PERMISSION_SET = SAFE
GO

but when i goto create the function with the following code it wont have it!

CREATE FUNCTION TransSICCode(@inpSIC varchar)
RETURNS varchar
AS EXTERNAL NAME
SICCodeTrans.SICTrans.TransSIC
GO

It gives me the following error message

Msg 6505, Level 16, State 1, Procedure TransSICCode, Line 1
Could not find Type 'SICTrans' in assembly 'SICCodeTrans'.

Any ideas??????????

Thanks

Marek Kluczynski