WPF: How to get a custom image ActualWidth value?

Question

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.NET4.5

Goal: To get an ActualWidth value of a custom image.
Problem: The ActualWidth value is always 0.
Question: How to get a right custom image ActualWidth value?
Code:

C#

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        this.Loaded += MainWindow_Loaded;
    }

    void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        MyImage myimage = new MyImage();
        MessageBox.Show(myimage.ActualWidth.ToString()); // 0
    }
}

class MyImage : Image
{
    protected override void OnRender(DrawingContext dc)
    {
        dc.DrawRectangle(Brushes.Red, null, new Rect(0, 0, 100, 100));
    }
}

Posted 29-Aug-15 2:17am

Ziya1995

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Ziya1995 · Accepted Answer · 2015-08-29T03:51:00

The size of the drawing (Rectangle) done by the DrawingContext is not the same thing as the size of the UIElement. There are no properties of the Image class nor the UIElement class that gets you the size of the drawing. You could define your own custom properties to be able to get the Height and Width of the drawn Rectangle:

C#

public class MyImage : Image
    {
        protected override void OnRender(DrawingContext dc)
        {
            dc.DrawRectangle(Brushes.Red, null, new Rect(0, 0, 100, 100));
            this.RectHeight = 100;
            this.RectWidth = 100;
        }

        public double RectHeight { get; private set; }
        public double RectWidth { get; private set; }
    }

Source:
https://social.msdn.microsoft.com/Forums/en-US/2f512dd6-cf81-46a6-ab38-e9f7cc483030/wpf-how-to-get-a-custom-image-actualwidth-value[^]