Why did it fail ,idispatch interface which get by AccessibleObjectFromEvent.call the idispatch's member

Question

I get a ms-word's handle，then use AccessibleObjectFromEvent to get is's IDispatch（late bingding）。then I want call it's property or method，it's fail。

but it's ok use c#.

How to use use late binding to get excel instance?

the code like this.

function GetProperty(dispobj: IDispatch; PropertyName: widestring;
    var retvalue: IDispatch): Boolean;
var
    hr: HResult;
    DispId1: Integer;
    value: Variant;
    params: TDispParams;
begin
    Result := false;
    hr := dispobj.GetIDsOfNames(GUID_NULL, @(PropertyName), 1,
        LOCALE_SYSTEM_DEFAULT, @DispId1);
    if (hr >= 0) then begin
        hr := dispobj.Invoke(DispId1, GUID_NULL, LOCALE_SYSTEM_DEFAULT,
            DISPATCH_PROPERTYGET, params, @value, nil, nil);
        if (hr >= 0) then begin
            retvalue := value;
            Result := true;
        end;
    end;
end;

    hWindow := GetWordHandle(Trim(LabeledEdit1.Text));
hWindow := GetChildWndHandle(hWindow, '_WwG');
if `AccessibleObjectFromWindow`(hWindow, 0, IID_IDispatch, WordObject) = S_OK then begin
    //GetProperty(WordObject, 'Application', WordApp);
   // WordObject.GetTypeInfoCount(nCount);
    //Showmessage(IntToStr(nCount));
    //WordApplication1.ConnectTo((WordObject.Application) as _Application);
   // Showmessage(WordObject.Application.Version)
    OleCheck(WordObject.QueryInterface(IID_IDispatch, WordApp));
    WordApplication1.ConnectTo(IDispatch(WordApp) as _Application);
    Showmessage(WordApplication1.Version)
end

Answer 1

@David Heffernan the full code：

procedure TMainForm.Button3Click(Sender: TObject);
var
  WordObject: IDispatch; // IDispatch;
  hWindow: hWnd;
  iWordApp: IDispatch;
  WordApp: _Application;
begin
  hWindow := GetWordHandle(Trim(LabeledEdit1.Text));
  hWindow := GetChildWndHandle(hWindow, '_WwG');
  if AccessibleObjectFromWindow(hWindow, 0, IID_IDispatch, WordObject) = S_OK
  then
  begin
    OleCheck(WordObject.QueryInterface(IID_IDispatch, iWordApp));
    WordApp :=  (iWordApp) as _Application;   // <--- interface not supported
    WordApplication1.ConnectTo(WordApp);
    Showmessage(WordApplication1.Version)
  end
end;

is translated from C# code。

How to use use late binding to get excel instance?