using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;using Autodesk;
using Autodesk.Revit;
using Autodesk.Revit.DB;
using Autodesk.Revit.UI;
using Autodesk.Revit.ApplicationServices;namespace APIAppStartup
{[Autodesk.Revit.Attributes.Transaction(Autodesk.Revit.Attributes.TransactionMode.Manual)][Autodesk.Revit.Attributes.Regeneration(Autodesk.Revit.Attributes.RegenerationOption.Manual)][Autodesk.Revit.Attributes.Journaling(Autodesk.Revit.Attributes.JournalingMode.NoCommandData)]public class AppSample:IExternalApplication{#region IExternalApplication Memberspublic Result OnShutdown(UIControlledApplication application){TaskDialog.Show("Revit", "Quit External Application!");return Result.Succeeded;}public Result OnStartup(UIControlledApplication application){string version = application.ControlledApplication.VersionName;//display splash window for 10 seconds
            SplashWindow.StartSplash();SplashWindow.ShowVersion(version);System.Threading.Thread.Sleep(10000);SplashWindow.StopSplash();return Result.Succeeded;}#endregion}
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;namespace APIAppStartup
{public delegate void DelegateCloseSplash();public partial class SplashWindow : Form{public SplashWindow(){InitializeComponent();m_delegateClose = new DelegateCloseSplash(InternalCloseSplash);}private DelegateCloseSplash m_delegateClose;private static SplashWindow m_instance;private static Thread InstanceCaller;//start a new thread to display splash windowpublic static void StartSplash(){m_instance = new SplashWindow();m_instance.TopMost = true;InstanceCaller = new Thread(new ThreadStart(MySplashThreadFunc));InstanceCaller.Start();}//kill the threadpublic static void StopSplash(){if (m_instance != null){m_instance.Invoke(m_instance.m_delegateClose);}}//show Revit version infopublic static void ShowVersion(string version){m_instance.Version.Text = version;}void InternalCloseSplash(){this.Close();this.Dispose();}//this is called by the new thread to show the splash screenprivate static void MySplashThreadFunc(){if (m_instance != null){m_instance.TopMost = true;m_instance.ShowDialog();}}}
}

<?xml version="1.0" encoding="utf-8"?>
<RevitAddIns><AddIn Type="Application"><Name>APIAppStartup</Name><Assembly>C:\Users\Administrator\documents\visual studio 2012\Projects\APIAppStartup\APIAppStartup\bin\Release\APIAppStartup.dll</Assembly><AddInId>502fe383-2648-4e98-adf8-5e6047f9dc34</AddInId><FullClassName>APIAppStartup.AppSample</FullClassName><VendorId>ADSK</VendorId><VendorDescription>http://xpvincent.cnblogs.com</VendorDescription></AddIn>
</RevitAddIns>