CREATE AGGREGATE Failed Because Type .. Does Not Conform To UDAGG Specification Due To Method 'Init'

I am trying to get the CLR user-defined aggregate functions sample working (VB version).

I've saved the sample (from Invoking CLR User-Defined Aggregate Functions ) to a .vb file and compiled it like this:



C:dataVStudioprojectsSQLutilsSQLutils>c:WINDOWSMicrosoft.NETFrameworkv2
.0.50727vbc /t:library /out: SQLutils.dll Class1.vb
Microsoft (R) Visual Basic Compiler versie 8.0.50727.42
voor Microsoft (R) .NET Framework versie 2.0.50727.42
Copyright (c) Microsoft Corporation. Alle rechten voorbehouden.



The SQLutils.dll file is created without warnings or errors.



I've created the assembly



create assembly sqlutildll from 'D:SQLdatadllSQLutils.dll'



and then the function:



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

EXTERNAL NAME sqlutildll.Concatenate



and then I got this error:



Msg 6558, Level 16, State 1, Line 1

CREATE AGGREGATE failed because type 'Concatenate' does not conform to UDAGG specification due to method 'Init'.

Msg 6597, Level 16, State 2, Line 1

CREATE AGGREGATE failed.



What is this UDAGG specification ?

How can I make this function working?



The VB code:




Code Snippet

Imports System

Imports System.Data

Imports Microsoft.SqlServer.Server

Imports System.Data.SqlTypes

Imports System.IO

Imports System.Text

<Serializable(), SqlUserDefinedAggregate(Format.UserDefined, IsInvariantToNulls:=True, IsInvariantToDuplicates:=False, IsInvariantToOrder:=False, MaxByteSize:=8000)> <Microsoft.VisualBasic.ComClass()> _

Public Class Concatenate

Implements IBinarySerialize

''' <summary>

''' The variable that holds the intermediate result of the concatenation

''' </summary>

Private intermediateResult As StringBuilder

''' <summary>

''' Initialize the internal data structures

''' </summary>

Public Sub Init()

Me.intermediateResult = New StringBuilder()

End Sub

''' <summary>

''' Accumulate the next value, not if the value is null

''' </summary>

''' <param name="value"></param>

Public Sub Accumulate(ByVal value As SqlString)

If value.IsNull Then

Return

End If

Me.intermediateResult.Append(value.Value).Append(","c)

End Sub

''' <summary>

''' Merge the partially computed aggregate with this aggregate.

''' </summary>

''' <param name="other"></param>

Public Sub Merge(ByVal other As Concatenate)

Me.intermediateResult.Append(other.intermediateResult)

End Sub

''' <summary>

''' Called at the end of aggregation, to return the results of the aggregation.

''' </summary>

''' <returns></returns>

Public Function Terminate() As SqlString

Dim output As String = String.Empty

'delete the trailing comma, if any

If Not (Me.intermediateResult Is Nothing) AndAlso Me.intermediateResult.Length > 0 Then

output = Me.intermediateResult.ToString(0, Me.intermediateResult.Length - 1)

End If

Return New SqlString(output)

End Function

Public Sub Read(ByVal r As BinaryReader) Implements IBinarySerialize.Read

intermediateResult = New StringBuilder(r.ReadString())

End Sub

Public Sub Write(ByVal w As BinaryWriter) Implements IBinarySerialize.Write

w.Write(Me.intermediateResult.ToString())

End Sub

End Class