DeploymentDownloadException Class

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);
            }
        }
    }
}