无法转换类型＆＃39; DataSourceDefinition＆＃39;的对象输入＆＃39; System.Collections.IEnumerable＆＃39;

Question

Ms 6522，Level 16，State 1，Line 4 执行用户定义的例程或聚合期间发生.NET Framework错误＆＃34; GetDataSourceContents2＆＃34;： System.InvalidCastException：无法转换类型＆＃39; SqlServerProject2.webservice.DataSourceDefinition＆＃39;输入＆＃39; System.Collections.IEnumerable＆＃39;。 System.InvalidCastException：    at SqlServerProject2.UserDefinedFunctions.GetDataSources2（String Datasourcename）

从下面的vb.net程序集运行clr函数时出现上述错误。有人可以帮忙吗？

Imports System
Imports System.Data
Imports System.Data.Sql
Imports System.Data.SqlClient
Imports System.Data.SqlTypes
Imports Microsoft.SqlServer.Server
Imports SqlServerProject2.webservice
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.Runtime.InteropServices

Partial Public Class UserDefinedFunctions

<SqlFunction(FillRowMethodName:="FillRow")> _
Public Shared Function GetDataSources2(ByVal Datasourcename As String) As IEnumerable

    Dim WS = New ReportingService2005
    WS.UseDefaultCredentials = True

    Dim DSContents As DataSourceDefinition = WS.GetDataSourceContents(Datasourcename)

    Return DSContents

End Function

Public Shared Sub FillRow(ByVal obj As Object, <Out()> ByRef ConnectString As SqlString)
    Dim DSContents As DataSourceDefinition = CType(obj, DataSourceDefinition)
    ConnectString = New SqlString(DSContents.ConnectString)
End Sub
End Class