AccessibleChildren returning null

Question

I am converting some VBA code that uses the AccessibleChildren method to C# but I am having some issues. The declaration looks like this:

[DllImport("oleacc.dll")]
    private static extern uint AccessibleChildren(IAccessible paccContainer, int iChildStart, int cChildren, [Out] object[] rgvarChildren, out int pcObtained);

The code that I am running looks like this:

private static object[] GetChildren(IAccessible element)
{
    const int firstchild = 2;
    int numChildren;
    int numReturned;

    numChildren = element.accChildCount;
    object[] childrenArray = null;

    if (numChildren > 0)
    {
        childrenArray = new object[numChildren];
        AccessibleChildren(element, firstchild, numChildren, childrenArray, out numReturned);
    }

    return childrenArray;
}

The problem is that when I call this method on a valid IAccessible (like the Ribbon in Word) childrenArray[0] is equal to null. Anyone have any ideas? One thought I had (or at least something that doesn't make sense to me) is that the VBA code passes the first element of the array:

Private Function GetChildren _
                 (Element As IAccessible) _
             As Variant()
    Const FirstChild        As Long = 0&
    Dim NumChildren         As Long
    Dim NumReturned         As Long
    Dim ChildrenArray()

    NumChildren = Element.accChildCount

    If NumChildren > 0 Then
    AccessibleChildren Element, FirstChild, NumChildren, _
                           ChildrenArray(0), NumReturned
    End If
    GetChildren = ChildrenArray
End Function

Thanks!

score 0 · Accepted Answer · answered Sep 30 '13 at 19:07

0

Apparently 0& is a way of representing a 32 bit long of the number 0. I'm not sure why I thought this was 2 but switching it to 0 seemed to fix it!

answered Sep 30 '13 at 19:07

Tom

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AccessibleChildren returning null

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