>一个PC上的多个实例被禁用.通过clickonce部署单个实例应用程序.当用户尝试启动应用程序的第二个实例时,会弹出一条消息,指示“另一个实例已经在运行”.
>异步检查更新,并安装更新(如果存在).如果用户运行新实例时有可用的更新,则会弹出“可用更新”.

构建演示应用程序的过程如下：

步骤1：使用Mutex类检测活动实例应用程序.

namespace ClickOnceDemo
{
    static class Program
    {
        /// summary>
        /// The main entry point for the application.
        /// /summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault( false );
            bool ok;
            var m = new System.Threading.Mutex( true,"Application",out ok );
            if ( !ok )
            {
                MessageBox.Show( "Another instance is already running.",ApplicationDeployment.CurrentDeployment.CurrentVersion.ToString() );
                return;
            }
           Application.Run( new UpdateProgress() );
        }
    }
}

步骤2：以编程方式处理更新

在我们这样做之前,我们应该禁用自动ClickOnce更新检查(在“发布 – 更新…”对话框中).

然后我们创建两个形式：UpdateProgress和mainForm,其中UpdateProgress指示下载进度,mainForm表示主应用程序.

当用户运行应用程序时,将首先启动updateProgress来检查更新.更新完成后,mainForm将启动,updateProgress将被隐藏.

namespace ClickOnceDemo
{
public partial class UpdateProgress : Form
 {
  public UpdateProgress()
        {
            InitializeComponent();
            Text = "Checking for updates...";

            ApplicationDeployment ad = ApplicationDeployment.CurrentDeployment;
            ad.CheckForUpdateCompleted += OnCheckForUpdateCompleted;
            ad.CheckForUpdateProgressChanged += OnCheckForUpdateProgressChanged;

            ad.CheckForUpdateAsync();
       }

        private void OnCheckForUpdateProgressChanged(object sender,DeploymentProgressChangedEventArgs e)
        {
            lblStatus.Text = String.Format( "Downloading: {0}. {1:D}K of {2:D}K downloaded.",GetProgressString( e.State ),e.BytesCompleted / 1024,e.BytesTotal / 1024 );
            progressBar1.Value = e.ProgressPercentage;
        }

        string GetProgressString( DeploymentProgressState state )
        {
            if ( state == DeploymentProgressState.DownloadingApplicationFiles )
            {
                return "application files";
            }
            if ( state == DeploymentProgressState.DownloadingApplicationInformation )
            {
                return "application manifest";
            }
            return "deployment manifest";
        }

        private void OnCheckForUpdateCompleted(object sender,CheckForUpdateCompletedEventArgs e)
        {
            if ( e.Error != null )
            {
                MessageBox.Show( "ERROR: Could not retrieve new version of the application. Reason: \n" + e.Error.Message + "\nPlease report this error to the system administrator." );
                return;
            }
            if ( e.Cancelled )
            {
                MessageBox.Show( "The update was cancelled." );
            }

            // Ask the user if they would like to update the application now.
            if ( e.UpdateAvailable )
            {
                if ( !e.IsUpdaterequired )
                {
                    long updateSize = e.UpdateSizeBytes;
                    DialogResult dr = MessageBox.Show( string.Format("An update ({0}K) is available. Would you like to update the application now?",updateSize/1024),"Update Available",MessageBoxButtons.OKCancel );
                    if ( DialogResult.OK == dr )
                    {
                        BeginUpdate();
                    }
                }
                else
                {
                    MessageBox.Show( "A mandatory update is available for your application. We will install the update now,after which we will save all of your in-progress data and restart your application." );
                    BeginUpdate();
                }
            }
            else
            {
                ShowMainForm();
            }
        }

        // Show the main application form
        private void ShowMainForm()
        {
            MainForm mainForm = new MainForm ();
            mainForm.Show();
            Hide();
        }

        private void BeginUpdate()
        {
            Text = "Downloading update...";
            ApplicationDeployment ad = ApplicationDeployment.CurrentDeployment;
            ad.UpdateCompleted += ad_UpdateCompleted;
            ad.UpdateProgressChanged += ad_UpdateProgressChanged;

            ad.UpdateAsync();
        }

        void ad_UpdateProgressChanged( object sender,DeploymentProgressChangedEventArgs e )
        {
            String progressText = String.Format( "{0:D}K out of {1:D}K downloaded - {2:D}% complete",e.BytesTotal / 1024,e.ProgressPercentage );
            progressBar1.Value = e.ProgressPercentage;
            lblStatus.Text = progressText;
        }

        void ad_UpdateCompleted( object sender,AsyncCompletedEventArgs e )
        {
            if ( e.Cancelled )
            {
                MessageBox.Show( "The update of the application's latest version was cancelled." );
                return;
            }
            if ( e.Error != null )
            {
                MessageBox.Show( "ERROR: Could not install the latest version of the application. Reason: \n" + e.Error.Message + "\nPlease report this error to the system administrator." );
                return;
            }

            DialogResult dr = MessageBox.Show( "The application has been updated. Restart? (If you do not restart now,the new version will not take effect until after you quit and launch the application again.)","Restart Application",MessageBoxButtons.OKCancel );
            if ( DialogResult.OK == dr )
            {
                Application.Restart();
            }
            else
            {
                ShowMainForm();
            }
        }
    }
}

该应用程序运行良好,我们希望这是一个很好的解决方案.
特别感谢Timothy Walters 提供的源代码