How do I know if a WPF window is opened

Question

In a WPF window, how do I know if it is opened?

My goal to open only 1 instance of the window at the time.

So, my pseudo code in the parent window is:

<

Answer 1

In WPF there is a collection of the open Windows in the Application class, you could make a helper method to check if the window is open.

Here is an example that will check if any Window of a certain Type or if a Window with a certain name is open, or both.

public static bool IsWindowOpen(string name = "") where T : Window
{
    return string.IsNullOrEmpty(name)
       ? Application.Current.Windows.OfType().Any()
       : Application.Current.Windows.OfType().Any(w => w.Name.Equals(name));
}

Usage:

if (Helpers.IsWindowOpen("MyWindowName"))
{
   // MyWindowName is open
}

if (Helpers.IsWindowOpen())
{
    // There is a MyCustomWindowType window open
}

if (Helpers.IsWindowOpen("CustomWindowName"))
{
    // There is a MyCustomWindowType window named CustomWindowName open
}