C#

<br />
	[StructLayout(LayoutKind.Sequential,CharSet=CharSet.Unicode)]<br />
	public struct OLECMDTEXT<br />
	{<br />
		public uint cmdtextf;<br />
		public uint cwActual;<br />
		public uint cwBuf;<br />
		[MarshalAs(UnmanagedType.ByValTStr,SizeConst=100)]public char rgwz;<br />
	}<br />
	[StructLayout(LayoutKind.Sequential)]<br />
	public struct OLECMD<br />
	{<br />
		public uint cmdID;<br />
		public uint cmdf;<br />
	}<br />
	[ComImport,<br />
	InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]<br />
	public interface IOleCommandTarget<br />
	{<br />
		void QueryStatus(ref Guid pguidCmdGroup, UInt32 cCmds,<br />
			[MarshalAs(UnmanagedType.LPArray, SizeParamIndex=1)] <br />
			OLECMD[] prgCmds, ref OLECMDTEXT CmdText);<br />
		void Exec(ref Guid pguidCmdGroup, uint nCmdId, uint nCmdExecOpt, <br />
			ref object pvaIn, ref object pvaOut);<br />
	}<br />
	[ClassInterface(ClassInterfaceType.None),<br />
	ComSourceInterfaces(typeof(COM_Events))]<br />
	public class COMAddin: IOleCommandTarget<br />
	{<br />
		// ....<br />
		public void QueryStatus(ref Guid pguidCmdGroup, <br />
				UInt32 cCmds, OLECMD[] prgCmds, ref OLECMDTEXT CmdText)<br />
		{<br />
			// ....<br />
		}<br />
		public void Exec(ref Guid pguidCmdGroup, uint nCmdId, <br />
				uint nCmdExecOpt, ref object pvaIn, ref object pvaOut)<br />
		{<br />
			// .... I would add here OnClick actions<br />
		}<br />
	}

TraceListener Listener=new EventLogTraceListener("myApp");
Trace.Listeners.Add(Listener);

...

void doSometing()
{
  try
  {
    //... do something 
  }
  catch(Exception e)
  {
    //... handle exception and write message to eventlog...
    Trace.WriteLine(e.Message,"Error");
  }
}