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ApplicationDeployment.CheckForUpdate Method

Checks UpdateLocation to determine whether a new update is available.

Namespace: System.Deployment.Application
Assembly: System.Deployment (in system.deployment.dll)

public bool CheckForUpdate ()
public boolean CheckForUpdate ()
public function CheckForUpdate () : boolean
Not applicable.

Return Value

true if a new update is available; otherwise, false.

Exception typeCondition

InvalidOperationException

ClickOnce throws this exception immediately if you call the CheckForUpdate method while an update is already in progress.

DeploymentDownloadException

The deployment manifest cannot be downloaded.

InvalidDeploymentException

The deployment manifest is corrupted. You will likely need to redeploy the application to fix this problem.

The CheckForUpdate method compares the version of the currently installed deployment with the version specified in the deployment manifest found at UpdateLocation. If the version on the server is different from the installed version, it returns true.

This method will block until the check has completed. To check for an update asynchronously, use the CheckForUpdateAsync method instead.

NoteNote:

If CheckForUpdate discovers that an update is available, and the user chooses not to install it, ClickOnce will prompt the user that an update is available the next time the application is run. There is no way to disable this prompting. (If the application is a required update, ClickOnce will install it without prompting.)

The following code example checks for an application update; if one is available, it installs it synchronously.

private void InstallUpdateSync()
{
    if (ApplicationDeployment.IsNetworkDeployed)
    {
        Boolean updateAvailable = false;
        ApplicationDeployment ad = ApplicationDeployment.CurrentDeployment;

        try
        {
            updateAvailable = ad.CheckForUpdate();
        }
        catch (DeploymentDownloadException dde)
        {
            // This exception occurs if a network error or disk error occurs
            // when downloading the deployment.
            MessageBox.Show("The application cannt check for the existence of a new version at this time. \n\nPlease check your network connection, or try again later. Error: " + dde);
            return;
        }
        catch (InvalidDeploymentException ide)
        {
            MessageBox.Show("The application cannot check for an update. The ClickOnce deployment is corrupt. Please redeploy the application and try again. Error: " + ide.Message);
            return;
        }
        catch (InvalidOperationException ioe)
        {
            MessageBox.Show("This application cannot check for an update. This most often happens if the application is already in the process of updating. Error: " + ioe.Message);
            return;
        }

        if (updateAvailable)
        {
            try
            {
                ad.Update();
                MessageBox.Show("The application has been upgraded, and will now restart.");
                Application.Restart();
            }
            catch (DeploymentDownloadException dde)
            {
                MessageBox.Show("Cannot install the latest version of the application. Either the deployment server is unavailable, or your network connection is down. \n\nPlease check your network connection, or try again later. Error: " + dde.Message);
            }
            catch (TrustNotGrantedException tnge)
            {
                MessageBox.Show("The application cannot be updated. The system did not grant the application the appropriate level of trust. Please contact your system administrator or help desk for further troubleshooting. Error: " + tnge.Message);
            }
        }
    }
}

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

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