hey all,
here is my question. i created this Oracle function i'd like to call in my VB.NET application, but i get the following error:

 "Specified cast is not valid."

First, here is the code for creating the Oracle function:

CREATE FUNCTION "ORDERITEMS" (ShippableItemID NUMBER) RETURN NUMBER is
inventory_count NUMBER;
enrollment_count NUMBER;

BEGIN
SELECT InventoryCount INTO inventory_count
FROM SHIPPABLEITEM
WHERE SHIPPABLEITEMID = ShippableItemID
AND Rownum = 1;

SELECT DISTINCT COUNT (COURSERECORD.StudentID) INTO enrollment_count
FROM COURSEINSTANCEMATERIALS, COURSERECORD
WHERE COURSEINSTANCEMATERIALS.ShippableItemID = ShippableItemID
AND COURSERECORD.CourseInstanceID = COURSEINSTANCEMATERIALS.CourseInstanceID;

IF (inventory_count < 0.5*enrollment_count) THEN
    RETURN 1;
ELSE
    RETURN 0;
END IF;
END;

I tested it in SQL *Plus and it worked fine. Now then, here is the part of my VB.NET code performing the call to the above function:

 DBCommand = New ADODB.Command
 DBRecords = New ADODB.Recordset
 DBCommand.ActiveConnection = DBLink

 Dim InputParameter As New ADODB.Parameter
 Dim ReturnValue As New ADODB.Parameter

 ItemIDValue = DBRecords.Fields(0).Value

 DBCommand.CommandText = "OrderItems"
 DBCommand.CommandType = ADODB.CommandTypeEnum.adCmdStoredProc

 InputParameter.Name = "ShippableItemID"
 InputParameter.Direction = ADODB.ParameterDirectionEnum.adParamInput
 InputParameter.Type = ADODB.DataTypeEnum.adInteger
 InputParameter.Value = ItemIDValue

 ReturnValue.Name = "myReturnValue"
 ReturnValue.Direction = ADODB.ParameterDirectionEnum.adParamReturnValue
 ReturnValue.Type = ADODB.DataTypeEnum.adInteger

 'Add parameters to ADODB command.
 DBCommand.Parameters.Append(InputParameter) --> ERROR ON THIS LINE
 DBCommand.Parameters.Append(ReturnValue)

 Try
    'Executes the command.
    DBFunctionResult = DBCommand.Execute()
 Catch ex As Exception
    MsgBox("Failed to call Oracle function ORDERITEMS.")
 End Try

 If Not DBFunctionResult.EOF Then
    Do Until DBFunctionResult.EOF
       ReturnFlag = DBFunctionResult.Fields(0).Value
       MsgBox("Function return value: " & ReturnFlag)
    Loop
 End If

I get the error in the line marked (DBCommand.Parameters.Append(InputParameter)). I tried setting the type of parameter InputParameter as adNumeric, but got the same error. Any ideas?

Thanks.