为了解决这个问题,我们构建了一个原型应用程序,它具有以下两个功能。
-
一台PC上的多个实例被禁用。通过ClickOnce部署单个实例应用程序。当用户试图启动应用程序的第二个实例时,将弹出一条消息,指示“另一个实例已在运行”。
-
异步检查更新,如果存在更新,则安装更新。如果用户运行新实例时有可用的更新,将弹出消息:“更新可用”。
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
在此之前,我们应该禁用自动的ClickOnce更新检查(在publish——updates……对话)。
然后我们创建两个表单:updateprogress和mainform,其中updateprogress表示下载进度,mainform表示主应用程序。
当用户运行应用程序时,将首先启动UpdateProgress以检查更新。更新完成后,将启动主窗体并隐藏更新进度。
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.BytesCompleted / 1024, 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();
}
}
}
}
这个应用程序运行良好,我们希望它是解决这个问题的好方法。
特别感谢
Timothy Walters
用于提供源代码
