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IContextMenu (Interfaces)
 
.
Summary
This interface is called by the Shell to either create or merge a shortcut menu associated with a Shell object.

C# Signature:

    [ComImport(),
    InterfaceType(ComInterfaceType.InterfaceIsIUnknown),
    GuidAttribute("000214e4-0000-0000-c000-000000000046")]
    public interface IContextMenu
    {
        [PreserveSig()]
        int QueryContextMenu(
            uint hMenu,
            uint indexMenu,
            int idCmdFirst,
            int idCmdLast,
            uint uFlags);

        [PreserveSig()]
        void InvokeCommand(IntPtr pici);

        [PreserveSig()]
        void GetCommandString(
            int idcmd,
            uint uflags,
            int reserved,
            StringBuilder commandstring,
            int cch);
    }

VB Signature:

<ComImport()> _
<InterfaceType(ComInterfaceType.InterfaceIsIUnknown)> _
<GuidAttribute("000214e4-0000-0000-c000-000000000046")> _
Public Interface IContextMenu
     <PreserveSig()> _
     Function QueryContextMenu( _
     ByVal hMenu As Integer, _
     ByVal indexMenu As Integer, _
     ByVal idCmdFirst As Integer, _
     ByVal idCmdLast As Integer, _
     ByVal uFlags As Integer) As Integer

     <PreserveSig()> _
     Sub InvokeCommand(ByVal pici As IntPtr)

     <PreserveSig()> _
     Sub GetCommandString( _
     ByVal idcmd As Integer, _
     ByVal uflags As Integer, _
     ByVal reserved As Integer, _
     ByVal commandstring As StringBuilder, _
     ByVal cch As Integer)
End Interface

Notes

In process shell extensions should never be written in managed code. There is no way for this to work correctly in all cases. Managed code may call shell extensions but cannot be used to implement them.

I found that GetCommandString gave me problems when defining the variable commandstring as a StringBuilder. (It had an unexplainable limit of 16 characters.) I found that by changing my definition to IntPtr, and then copying a

string into this pointer by using lstrcpy works for the true buffer size designated by cch.

Hint:

You may have to explicitly call lstrcpynW or lstrcpynA based uFlags

Sample Code:

  void IContextMenu.GetCommandString(int idCmd, uint uFlags, int reserved,  IntPtr commandString, int cchMax)
  {
    string commandStr = "" ;
    if ((uFlags & (uint)GCS.VERB) != 0)
    {
        //obviously you could insert some cases here
        switch (idCmd)
        {
            default:
                commandStr = "...";
                break;
        }
    }
    if((uFlags  & (uint)GCS.HELPTEXT) != 0)
    {
        switch (idCmd)
        {
            case 0:
                commandStr = "Menu Item 1. And a brief description of what it does.";
                break;
            case 1:
                commandStr = "Menu Item 2. And a brief description of what it does." ;
                break;
            case 2:
                commandStr = "Menu Item 3. And a brief description of what it does.";
                break;
            case 3:
                commandStr = "Menu Item 4. And a brief description of what it does.";
                break;
            default:
                commandStr = "...";
                break;
        }
    }

    // must limit the return string to cchMax
    if (commandStr.Length >= cchMax) commandStr = commandStr.Substring(0, cchMax-1) ;

    // now return unicode or ansi based on uFlags
    if((uFlags  & (uint)GCS.UNICODE) != 0 )
    {
        str = Marshal.StringToHGlobalUni(commandStr);
        Helpers.lstrcpynW(commandString, str, cchMax);
        Marshal.FreeHGlobal(str);
    }
    else
    {
        str = Marshal.StringToHGlobalAnsi(commandStr);
        Helpers.lstrcpynA(commandString, str, cchMax);
        Marshal.FreeHGlobal(str);
    }
  }

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