Simple logging dockable window with a custom context menu
ClearLoggingCommand.cs
// Copyright 2012 ESRI
// 
// All rights reserved under the copyright laws of the United States
// and applicable international laws, treaties, and conventions.
// 
// You may freely redistribute and use this sample code, with or
// without modification, provided you include the original copyright
// notice and use restrictions.
// 
// See the use restrictions.
// 

using System;
using System.Drawing;
using System.Runtime.InteropServices;
using ESRI.ArcGIS.ADF.BaseClasses;
using ESRI.ArcGIS.ADF.CATIDs;
using ESRI.ArcGIS.Framework;
using ESRI.ArcGIS.ArcMapUI;
using ESRI.ArcGIS.esriSystem;

namespace SimpleLogWindowCS
{
    /// <summary>
    /// Summary description for ClearLoggingCommand.
    /// </summary>
    [Guid("b5820a63-e3d4-42a1-91c5-d90eacc3985b")]
    [ClassInterface(ClassInterfaceType.None)]
    [ProgId("SimpleLogWindowCS.ClearLoggingCommand")]
    public sealed class ClearLoggingCommand : BaseCommand
    {
        #region COM Registration Function(s)
        [ComRegisterFunction()]
        [ComVisible(false)]
        static void RegisterFunction(Type registerType)
        {
            // Required for ArcGIS Component Category Registrar support
            ArcGISCategoryRegistration(registerType);

            //
            // TODO: Add any COM registration code here
            //
        }

        [ComUnregisterFunction()]
        [ComVisible(false)]
        static void UnregisterFunction(Type registerType)
        {
            // Required for ArcGIS Component Category Registrar support
            ArcGISCategoryUnregistration(registerType);

            //
            // TODO: Add any COM unregistration code here
            //
        }

        #region ArcGIS Component Category Registrar generated code
        /// <summary>
        /// Required method for ArcGIS Component Category registration -
        /// Do not modify the contents of this method with the code editor.
        /// </summary>
        private static void ArcGISCategoryRegistration(Type registerType)
        {
            string regKey = string.Format("HKEY_CLASSES_ROOT\\CLSID\\{{{0}}}", registerType.GUID);
            MxCommands.Register(regKey);
            GxCommands.Register(regKey);
            GMxCommands.Register(regKey);
            SxCommands.Register(regKey);

        }
        /// <summary>
        /// Required method for ArcGIS Component Category unregistration -
        /// Do not modify the contents of this method with the code editor.
        /// </summary>
        private static void ArcGISCategoryUnregistration(Type registerType)
        {
            string regKey = string.Format("HKEY_CLASSES_ROOT\\CLSID\\{{{0}}}", registerType.GUID);
            MxCommands.Unregister(regKey);
            GxCommands.Unregister(regKey);
            GMxCommands.Unregister(regKey);
            SxCommands.Unregister(regKey);

        }

        #endregion
        #endregion

        private IApplication m_application;
        public ClearLoggingCommand()
        {
            base.m_category = ".NET Samples";
            base.m_caption = "Clear Log (C#)";
            base.m_message = "Clear items in logging dockable window";
            base.m_toolTip = "Clear log";
            base.m_name = "CSNETSamples_ClearLogCommand";
        }

        #region Overriden Class Methods

        /// <summary>
        /// Occurs when this command is created
        /// </summary>
        /// <param name="hook">Instance of the application</param>
        public override void OnCreate(object hook)
        {
            if (hook == null)
                return;

            m_application = hook as IApplication;
        }

        /// <summary>
        /// Occurs when this command is clicked
        /// </summary>
        public override void OnClick()
        {
            //This command is designed to be on a context menu displayed when the 
            //logging window is right-clicked. Get the context item of the application
            IDocument doc = m_application.Document;
            object contextItem = null;
            if (doc is IBasicDocument)
            {
                contextItem = ((IBasicDocument)doc).ContextItem;
            }

            IDockableWindow dockWin = null;
            UID logWindowID = new UIDClass();
            logWindowID.Value = "{600cb3c8-e9d8-4c20-b2c7-f97082b10f92}";

            if (contextItem != null && contextItem is IDockableWindow)
            {
                dockWin = (IDockableWindow)contextItem;
            }
            else //In the case of ArcCatalog or the command has been placed outside the designated context menu
            {
                //Get the dockable window directly
                IDockableWindowManager dockWindowManager = (IDockableWindowManager)m_application;
                dockWin = dockWindowManager.GetDockableWindow(logWindowID);
            }

            //Clear list items in the dockable window
            if (dockWin != null && dockWin.ID.Compare(logWindowID))
            {
                System.Windows.Forms.ListBox containedBox = dockWin.UserData as System.Windows.Forms.ListBox;
                containedBox.Items.Clear();
            }

        }

        #endregion
    }
}