SQL Server Can't Find Classname In DLL?

I am trying to get the CLR user-defined aggregate functions sample working.



I have made the DLL and I can create the assembly,



create assembly sqlutildll from 'D:SQLdatadllSQLutils.dll'



This went OK. But I can't create the function:



CREATE AGGREGATE Concat (@input nvarchar(200)) RETURNS nvarchar(max)

EXTERNAL NAME sqlutildll.Concatenate



this is the error:



Msg 6556, Level 16, State 1, Line 1

CREATE AGGREGATE failed because it could not find type 'Concatenate' in assembly 'SQLutils'.

Msg 6597, Level 16, State 2, Line 1

CREATE AGGREGATE failed.



This looks like a simple error, but the name Concatenate is spelled correctly (it is a copy from books online see "Invoking CLR User-Defined Aggregate Functions" in BOL)



The error is "could not find type", but it is a class, might this be the problem?