assets/samples/Samples/ModelessDialog/ModelessForm_ExternalEvent/CS/Application.cs

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using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.IO;

using Autodesk;
using Autodesk.Revit;
using Autodesk.Revit.DB;
using Autodesk.Revit.UI;
using Autodesk.Revit.ApplicationServices;

namespace Revit.SDK.Samples.ModelessForm_ExternalEvent.CS
{
    /// <summary>
    /// Implements the Revit add-in interface IExternalApplication
    /// </summary>
    public class Application : IExternalApplication
    {
        // class instance
        internal static Application thisApp = null;
        // ModelessForm instance
        private ModelessForm m_MyForm;

        #region IExternalApplication Members
        /// <summary>
        /// Implements the OnShutdown event
        /// </summary>
        /// <param name="application"></param>
        /// <returns></returns>
        public Result OnShutdown(UIControlledApplication application)
        {
            if (m_MyForm != null && m_MyForm.Visible)
            {
                m_MyForm.Close();
            }

            return Result.Succeeded;
        }

        /// <summary>
        /// Implements the OnStartup event
        /// </summary>
        /// <param name="application"></param>
        /// <returns></returns>
        public Result OnStartup(UIControlledApplication application)
        {
            m_MyForm = null;   // no dialog needed yet; the command will bring it
            thisApp = this;  // static access to this application instance

            return Result.Succeeded;
        }

        /// <summary>
        ///   This method creates and shows a modeless dialog, unless it already exists.
        /// </summary>
        /// <remarks>
        ///   The external command invokes this on the end-user's request
        /// </remarks>
        /// 
        public void ShowForm(UIApplication uiapp)
        {
            // If we do not have a dialog yet, create and show it
            if (m_MyForm == null || m_MyForm.IsDisposed)
            {
                // A new handler to handle request posting by the dialog
                RequestHandler handler = new RequestHandler();

                // External Event for the dialog to use (to post requests)
                ExternalEvent exEvent = ExternalEvent.Create(handler);

                // We give the objects to the new dialog;
                // The dialog becomes the owner responsible fore disposing them, eventually.
                m_MyForm = new ModelessForm(exEvent, handler);
                m_MyForm.Show();
            }
        }


        /// <summary>
        ///   Waking up the dialog from its waiting state.
        /// </summary>
        /// 
        public void WakeFormUp()
        {
            if (m_MyForm != null)
            {
                m_MyForm.WakeUp();
            }
        }
        #endregion
    }
}