3

I'm learning WPF, and seem to have found something a little odd, which I can't find the reason to anywhere I've searched.

I have a window with one checkbox on it called "chkTest". I have it set to be true by default.

The following code is what I don't understand. Basically I'm trying to set the "chkTest" control to a control I create on the fly. The message box displays the value I set in code, but the control on the window is still set to be true.

Can someone explain the process behind this?

public partial class Window1 : Window
{
    public Window1()
    {
        InitializeComponent();

        CheckBox chk = new CheckBox();
        chk.IsChecked = false;

        this.chkTest = chk;

        MessageBox.Show(chk.IsChecked.Value.ToString());
    }
}

Thanks

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2 Answers 2

Reset to default
3

This is because you're fooling the DependencyProperty system by doing this - remember, getters/setters of DP properties work differently than regular properties. The UI has a trigger on the IsChecked property, but you replace the whole object. Since you didn't actually change IsChecked on the visible checkbox, the trigger doesn't fire and the UI isn't updated.

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3

Here's one way to go about it. First, you give a name to your main Grid - say, LayoutRoot:

<Grid x:Name="LayoutRoot">
    <CheckBox x:Name="chkTest" IsChecked="True"></CheckBox>
</Grid>

Then, you say:

public partial class Window1 : Window
{
    public Window1()
    {
        InitializeComponent();

        CheckBox chk = new CheckBox();
        chk.IsChecked = false;

        LayoutRoot.Children.Remove(chkTest);
        LayoutRoot.Children.Add(chk);
    }
}

And you're done.

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