CODEWITHSUNDEEP
c#wpfsingle-instance
user3342256
user3342256

Reputation: 1290

Checking if a MainWindow already exists

I have a C#/WPF application that consists of a mainwindow and a system tray icon. I have configured App.xaml with ShutdownMode="OnExplicitShutdown" in order to keep the application running in the system tray upon closing the main window.

In the context menu of the system tray icon, I have menu items bound to methods that re-open the main Window:

private void SysTray_Information_Click(object sender, RoutedEventArgs e)
{
    var newWindow = new MainWindow();
    newWindow.Show();
    MainWindow.Focus();
}

I would like to add to these methods a check to see if the mainwindow is already being displayed (hasn't been closed). Otherwise it will be possible to open multiple copies of the mainwindow. How can I achieve this?

Upvotes: 0

Views: 784

Answers (2)

Ross Bush
Ross Bush

Reputation: 15155

A semaphore or a mutex would be appropriate at the application level. This code is for a WinForms app but I am sure it can be modified to suite your needs.

static void Main()
{
    System.Threading.Mutex appMutex = new System.Threading.Mutex(true, "MyApplicationName", out exclusive);
    if (!exclusive)
    {
        MessageBox.Show("Another instance of My Program is already running.","MyApplicationName",MessageBoxButtons.OK,MessageBoxIcon.Exclamation );
        return;
    }
    Application.Run(new frmMyAppMain());
    GC.KeepAlive(appMutex);
}

Upvotes: 2

McGarnagle
McGarnagle

Reputation: 102723

It sounds like you could use a static variable for this: 

public class MainWindow : Window
{
    private static bool _isInstanceDisplayed = false;
    public static bool IsInstanceDisplayed() { return _isInstanceDisplayed; }
}

Set it to true when you load the window. Then you can check as needed using:

if (MainWindow.IsInstanceDisplayed()) { ... }

Upvotes: 1

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