CODEWITHSUNDEEP
c#wpf
Andrew
Andrew

Reputation: 173

Accessing owner window methods in WPF

I basically want to access methods of owner window, but I get a Null Reference Exception

How does it look like now: I have my MainWindow with public WriteLine method

public partial class MainWindow : Window
{
    public void WriteLine(string text, params object[] args)
    {
        text = String.Format(text, args);
        outputBox.AppendText(text + "\r\n");
    }

    private void ShowPlot()
    {
        PlotWindow plotWindow = new PlotWindow();
        plotWindow.writeline += WriteLine;
        plotWindow.Owner = this;
        plotWindow.Show();
    }
}

Then in PlotWindow class I am trying to call WriteLine with these lines:

writeline("Drawing plot");
(Owner as MainWindow).WriteLine("Drawing plot");

As you can see, I'm calling it through Owner property and through using the delegate writeline in PlotWindow. Any of these approaches gives me a System.NullReferenceException

What am I missing?

Upvotes: 0

Views: 689

Answers (1)

Titian Cernicova-Dragomir
Titian Cernicova-Dragomir

Reputation: 250106

As you state in the comments, you invoke the Owner property from a method invoked by the constructor. This means you try to access values you have not set yet.

    PlotWindow plotWindow = new PlotWindow(); // This is where you try to access the Owner, this is where the constructor is invoked
    plotWindow.writeline += WriteLine;
    plotWindow.Owner = this; // This is where you set the owner
    plotWindow.Show();

Consider using an event that occurs after the window is shown, such as the Loaded event

Upvotes: 1

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