Hi i have an application hosting webbrowser control in design mode. I also
wrote a custom OleUndoManger. My problem is if I move or resize a html
element the application crashes. With NullPointerException.

Can anybody check if the definition is correct?

TIA dom

Please respond on
d-dot-mohl-at-hico-dot-com

Here is my definition of the ole interfaces:

[ComVisible(true), Guid("B3E7C340-EF97-11CE-9BC9-00AA00608E01"),
InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IEnumOleUndoUnits {
[return: MarshalAs(UnmanagedType.I4)]
[PreserveSig]
int Next(
[In, MarshalAs(UnmanagedType.U4)]
int numDesired,
[Out, MarshalAs(UnmanagedType.Interface)]
out IOleUndoUnit unit,
[Out, MarshalAs(UnmanagedType.U4)]
out int numReceived);

[PreserveSig]
int Skip(
[In, MarshalAs(UnmanagedType.I4)]
int numToSkip);

[PreserveSig]
int Reset();

[PreserveSig]
int Clone(
[Out, MarshalAs(UnmanagedType.Interface)]
out IEnumOleUndoUnits enumerator);
};

[ComVisible(true), Guid("A1FAF330-EF97-11CE-9BC9-00AA00608E01"),
InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
public interface IOleParentUndoUnit : IOleUndoUnit {
[return: MarshalAs(UnmanagedType.I4)]
[PreserveSig]
int Open(
[In, MarshalAs(UnmanagedType.Interface)]
IOleParentUndoUnit parentUnit);
[return: MarshalAs(UnmanagedType.I4)]
[PreserveSig]
int Close(
[In, MarshalAs(UnmanagedType.Interface)]
IOleParentUndoUnit parentUnit,
[In, MarshalAs(UnmanagedType.Bool)]
bool fCommit);
[return: MarshalAs(UnmanagedType.I4)]
[PreserveSig]
int Add(
[In, MarshalAs(UnmanagedType.Interface)]
IOleUndoUnit undoUnit);
[return: MarshalAs(UnmanagedType.I4)]
[PreserveSig]
int FindUnit(
[In, MarshalAs(UnmanagedType.Interface)]
IOleUndoUnit undoUnit);
[return: MarshalAs(UnmanagedType.I4)]
[PreserveSig]
int GetParentState(
[Out, MarshalAs(UnmanagedType.I4)]
out int state
);
}
[ComVisible(true), ComImport(),
Guid("6D5140C1-7436-11CE-8034-00AA006009FA"),
InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
public interface IOleServiceProvider {
[return: MarshalAs(UnmanagedType.I4)]
[PreserveSig]
int QueryService(
[In] ref Guid guidService,
[In] ref Guid riid,
out IntPtr ppvObject);
}
[ComVisible(true), Guid("D001F200-EF97-11CE-9BC9-00AA00608E01"),
InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
public interface IOleUndoManager {
[PreserveSig]
int Open(
[In, MarshalAs(UnmanagedType.Interface)]
IOleParentUndoUnit parentUndo);
[PreserveSig]
int Close(
[In, MarshalAs(UnmanagedType.Interface)]
IOleParentUndoUnit parentUndo,
[In, MarshalAs(UnmanagedType.Bool)]
bool fCommit);
[PreserveSig]
int Add(
[In, MarshalAs(UnmanagedType.Interface)]
IOleUndoUnit undoUnit);
[return: MarshalAs(UnmanagedType.I4)]
int GetOpenParentState();
[PreserveSig]
int DiscardFrom(
[In, MarshalAs(UnmanagedType.Interface)]
IOleUndoUnit undoUnit);
void UndoTo(
[In, MarshalAs(UnmanagedType.Interface)]
IOleUndoUnit undoUnit);
void RedoTo(
[In, MarshalAs(UnmanagedType.Interface)]
IOleUndoUnit undoUnit);
[return: MarshalAs(UnmanagedType.Interface)]
IEnumOleUndoUnits EnumUndoable();
[return: MarshalAs(UnmanagedType.Interface)]
IEnumOleUndoUnits EnumRedoable();
[return: MarshalAs(UnmanagedType.BStr)]
string GetLastUndoDescription();
[return: MarshalAs(UnmanagedType.BStr)]
string GetLastRedoDescription();
void Enable(
[In, MarshalAs(UnmanagedType.Bool)]
bool fEnable);
}
[ComVisible(true), Guid("894AD3B0-EF97-11CE-9BC9-00AA00608E01"),
InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
public interface IOleUndoUnit {
[return: MarshalAs(UnmanagedType.I4)]
[PreserveSig]
int Do(
[In, MarshalAs(UnmanagedType.Interface)]
IOleUndoManager undoManager);
[return: MarshalAs(UnmanagedType.I4)]
[PreserveSig]
int GetDescription(
[Out, MarshalAs(UnmanagedType.BStr)]
out string bStr);
[return: MarshalAs(UnmanagedType.I4)]
[PreserveSig]
int GetUnitType(
[Out]
out Guid clsid,
[Out, MarshalAs(UnmanagedType.I4)]
out int plID);
[return: MarshalAs(UnmanagedType.I4)]
[PreserveSig]
int OnNextAdd();
}

[quoted text, click to view]

Since it's legal to pass a NULL pointer for numRecieved, you should
declare the last parameter as an IntPtr passed by value. You can then
write the number of returned elements with Marshal.WriteInt32().


[quoted text, click to view]

Interface inheritance doesn't work as you expect with COM interop.
IOleParentUndoUnit must redeclare all methods from the IOleUndoUnit
interface.


And finally, you ought to mark these interfaces with the ComImport
attribute.



Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com