Retrieving an array of objects from COM object.
Hi all,
I'm trying to pass an array of objects from a COM dll written in VB.Net, to a VB6 app. The point of this excersize is that's it's analogous to the behaviour of a web service client I'm writing to make web services available to a vb6 app.
This snippet illustrates the problem I'm having. Full code below.
Code:
Dim Tester As New DotNetCOMTest.Class2
Dim TesterObjectArray() As TestClass
' Attempt to get an array of objects
TesterObjectArray = Tester.GetTestClasses ' Type Mismatch
Set TesterObjectArray = Tester.GetTestClasses ' Can't assign to array
Set TesterObjectArray() = Tester.GetTestClasses ' Can't assign to array
Is what I'm trying to do possible and I'm simply doing it wrong? If not I'll fall back to holding the array in the COM object and pulling out the items one at a time (which works ok).
VB.Net COM Class definition:
PHP Code:
Imports System
Imports System.Runtime.InteropServices
Namespace Tester
<Guid("89439AD1-756F-4f9c-BFB4-18236F63251E"), InterfaceType(ComInterfaceType.InterfaceIsIDispatch)> _
Public Interface _Class2
<DispId(5)> Function LoopBack(ByRef b() As Integer) As Integer()
<DispId(3)> Function GetTestClass() As TestClass
<DispId(4)> Function GetTestClasses() As TestClass()
End Interface
<Guid("1376DE24-CC2D-46cb-8BF0-887A9CAF3014"), _
ClassInterface(ClassInterfaceType.None), _
ProgId("Tester.Test1")> Public Class Class2
Implements _Class2
Public Function GetTestClass() As TestClass Implements _Class2.GetTestClass
Return New TestClass
End Function
Public Function GetTestClasses() As TestClass() Implements _Class2.GetTestClasses
Dim Classes(2) As TestClass
Classes(1) = New TestClass
Classes(2) = New TestClass
Return Classes
End Function
Public Function LoopBack(ByRef b() As Integer) As Integer() Implements _Class2.LoopBack
Return b
End Function
End Class
<Guid("89439AD1-756F-4f9c-BFB4-18236F63251F"), _
InterfaceType(ComInterfaceType.InterfaceIsIDispatch)> _
Public Interface _TestClass
<DispId(1)> Property TestInt() As Integer
<DispId(2)> Property TestString() As String
<DispId(3)> Property TestDouble() As Double
<DispId(4)> Sub DumpVars()
End Interface
<Guid("1376DE24-CC2D-46cb-8BF0-887A9CAF3015"), _
ClassInterface(ClassInterfaceType.None), _
ProgId("Tester.TestClass")> Public Class TestClass
Implements _TestClass
Dim lString As String
Dim lInt As Integer
Dim lDouble As Double
Public Property TestInt() As Integer Implements _TestClass.TestInt
Get
Return lInt
End Get
Set(ByVal value As Integer)
lInt = value
End Set
End Property
Public Property TestString() As String Implements _TestClass.TestString
Get
Return lString
End Get
Set(ByVal value As String)
lString = value
End Set
End Property
Public Property TestDouble() As Double Implements _TestClass.TestDouble
Get
Return lDouble
End Get
Set(ByVal value As Double)
lDouble = value
End Set
End Property
Public Sub DumpVars() Implements _TestClass.DumpVars
MsgBox("String = " + lString + " Int = " + lInt.ToString + " Double = " + lDouble.ToString)
End Sub
End Class
End Namespace
VB6 Client form:
Code:
Private Sub Form_Load()
Dim TesterObject As TestClass
Dim y() As Long
Dim z() As Long
Dim i As Integer
ReDim y(5) As Long
y(0) = 123
y(1) = 222
y(2) = 333
' Receiving a primative array from a COM object.
z = Tester.LoopBack(y)
' See if our values have been preserved
For i = 0 To UBound(z) - 1
Debug.Print "Z" & i & " = " & z(i)
Next i
' Get an instance of a UDT
Set TesterObject = Tester.GetTestClass
TesterObject.DumpVars
Dim Tester As New DotNetCOMTest.Class2
Dim TesterObjectArray() As TestClass
' Attempt to get an array of objects
TesterObjectArray = Tester.GetTestClasses ' Type Mismatch
Set TesterObjectArray = Tester.GetTestClasses ' Can't assign to array
Set TesterObjectArray() = Tester.GetTestClasses ' Can't assign to array
For i = 0 To UBound(d) - 1
d(i).DumpVars
Next i
End Sub
Re: Retrieving an array of objects from COM object.
2 ways spring to mind from memory/without being able to test them from this end, but what about
Code:
Dim Tester As New DotNetCOMTest.Class2
Dim TesterObjectArray() As DotNetCOMTest.TestClass
TesterObjectArray = Tester.GetTestClasses
' Or
Dim Tester As New DotNetCOMTest.Class2
Dim TesterObjectArray() As Object
TesterObjectArray = Tester.GetTestClasses
Alternatively, exporting this as a collection as opposed to an array perhaps?
Re: Retrieving an array of objects from COM object.
Thanks for the response Alex,
Your first suggestion still throws a "Type Mismatch" error, and the second throws a "Can't assign to array"
I tried briefly to export a collection, namely an instance of
System.Collections.ObjectModel.Collection<TestClass>
and received a compiler warning
Quote:
Warning 1 Type library exporter warning processing 'Tester._TestCollectionClass.GetCol(#0), Tester'. Warning: Type library exporter encountered a generic type instance in a signature. Generic code may not be exported to COM.
In the meantime I'm working around the issue with a trivial kludge fix in the form of a class called ArrayWrapper which is passed an array on instantiation (they're instantiated within the .Net library) and implements .Item() and .Count so I can fetch the wrapped objects one at a time.
