IContextMenu::GetCommandString Not showing help text in Windows Explorer

Question

Hi, i am implementing a shell context menu for windows explorer and have successfully created the menu's. What i am having trouble with is the IContextMenu::GetCommandString method that displays the help text in the status bar when you hover over the selected menu item.

When i do hover over each item nothing is displayed, but whats weird is that some of the other items that i didnt create, eg - open, or print have had their help text turned into garbage..

Here is a code sample of IContextMenu::QueryContextMenu & IContextMenu::GetCommandString..

int ShellExtLib.IContextMenu.QueryContextMenu(IntPtr hMenu, uint indexMenu, uint idCmdFirst, uint idCmdLast, uint uFlags)
{
    uint idCmd = idCmdFirst;
    StringBuilder sb = new StringBuilder(1024);

    try
    {
        if ((uFlags & 0xf) == 0 || (uFlags & (uint)ShellExtLib.CMF.CMF_EXPLORE) != 0)
        {
            uint selectedFileCount = Helpers.DragQueryFile(m_hDrop, 0xffffffff, null, 0);

            if (selectedFileCount == 1)
            {
                Helpers.DragQueryFile(m_hDrop, 0, sb, sb.Capacity + 1);
                Documents.Add(sb.ToString());
            }
            else
            {
                // MULTIPLE FILES SELECTED.
                for (uint i = 0; i < selectedFileCount; i++)
                {
                    Helpers.DragQueryFile(m_hDrop, i, sb, sb.Capacity + 1);
                    Documents.Add(sb.ToString());
                }
            }

            Helpers.InsertMenu(hMenu, indexMenu++, ShellExtLib.UFLAGS.MF_SEPARATOR | ShellExtLib.UFLAGS.MF_BYPOSITION, 0, null);

            IntPtr hSubMenu = Helpers.CreateMenu();
            if (hSubMenu != IntPtr.Zero)
            {
                Helpers.InsertMenu(hSubMenu, 0, ShellExtLib.UFLAGS.MF_STRING | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, "Item 1");
                Helpers.InsertMenu(hSubMenu, 1, ShellExtLib.UFLAGS.MF_STRING | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, "Item 2");
                Helpers.InsertMenu(hSubMenu, 2, ShellExtLib.UFLAGS.MF_SEPARATOR | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, null);
                Helpers.InsertMenu(hSubMenu, 3, ShellExtLib.UFLAGS.MF_STRING | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, "Item 3");
                Helpers.InsertMenu(hSubMenu, 4, ShellExtLib.UFLAGS.MF_SEPARATOR | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, null);
                Helpers.InsertMenu(hSubMenu, 5, ShellExtLib.UFLAGS.MF_STRING | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, "Item 4");
                Helpers.InsertMenu(hSubMenu, 6, ShellExtLib.UFLAGS.MF_STRING | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, "Item 5");
            }

            Helpers.InsertMenu(hMenu, indexMenu++, ShellExtLib.UFLAGS.MF_STRING | ShellExtLib.UFLAGS.MF_BYPOSITION | ShellExtLib.UFLAGS.MF_POPUP, (uint)hSubMenu, "Main Menu");

            Helpers.InsertMenu(hMenu, indexMenu++, ShellExtLib.UFLAGS.MF_SEPARATOR | ShellExtLib.UFLAGS.MF_BYPOSITION, 0, null);

            return (int)(idCmd - idCmdFirst);
        }
    }
    catch { }

    return 0;
}



void ShellExtLib.IContextMenu.GetCommandString(int idCmd, uint uFlags, int pwReserved, StringBuilder commandString, int cchMax)
    {
        switch (uFlags)
        {
            case (uint)ShellExtLib.GCS.VERB:
                commandString = new StringBuilder("x");
                break;

            case (uint)ShellExtLib.GCS.HELPTEXTA:
                commandString = new StringBuilder("y");
                break;
        }
    }

Does anyone have any suggestions? I have read a number of articles on how to build shell extensions and have also been reading MSDN as well..

Thanks.

Answer 1

Your declaration of GetCommandString is incorrect - GetCommandString passes its own buffer where you are supposed to copy the string. I don't think you can declare it as StringBuilder in this case. Declare it as IntPtr and then use Encoding.Unicode.GetBytes and Marshal.Copy to copy your string to the buffer - be sure to add the null terminator.