WPF Databinding CheckBox.IsChecked

Question

How would I bind the IsChecked member of a CheckBox to a member variable in my form?

(I realize I can access it directly, but I am trying to learn about databinding and WPF)

Below is my failed attempt to get this working.

XAML:

<Window x:Class="MyProject.Form1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Title" Height="386" Width="563" WindowStyle="SingleBorderWindow">
<Grid>
    <CheckBox Name="checkBoxShowPending" 
              TabIndex="2" Margin="0,12,30,0" 
              Checked="checkBoxShowPending_CheckedChanged" 
              Height="17" Width="92" 
              VerticalAlignment="Top" HorizontalAlignment="Right" 
              Content="Show Pending" IsChecked="{Binding ShowPending}">
    </CheckBox>
</Grid>
</Window>

Code:

namespace MyProject
{
    public partial class Form1 : Window
    {
        private ListViewColumnSorter lvwColumnSorter;

        public bool? ShowPending
        {
            get { return this.showPending; }
            set { this.showPending = value; }
        }

        private bool showPending = false;

        private void checkBoxShowPending_CheckedChanged(object sender, EventArgs e)
        {
            //checking showPending.Value here.  It's always false
        }
    }
}

Solution 1

<Window ... Name="MyWindow">
  <Grid>
    <CheckBox ... IsChecked="{Binding ElementName=MyWindow, Path=ShowPending}"/>
  </Grid>
</Window>

Note i added a name to <Window>, and changed the binding in your CheckBox. You will need to implement ShowPending as a DependencyProperty as well if you want it to be able to update when changed.

Solution 2

Addendum to @Will's answer: this is what your DependencyProperty might look like (created using Dr. WPF's snippets):

#region ShowPending

/// <summary>
/// ShowPending Dependency Property
/// </summary>
public static readonly DependencyProperty ShowPendingProperty =
    DependencyProperty.Register("ShowPending", typeof(bool), typeof(MainViewModel),
        new FrameworkPropertyMetadata((bool)false));

/// <summary>
/// Gets or sets the ShowPending property. This dependency property 
/// indicates ....
/// </summary>
public bool ShowPending
{
    get { return (bool)GetValue(ShowPendingProperty); }
    set { SetValue(ShowPendingProperty, value); }
}

#endregion

Comments

[Pat]

If the property is in a ViewModel rather than the View itself, how would you do the binding?

[Will Eddins]

If using a ViewModel, you would typically set your DataContext within your View (or in the XAML) to your ViewModel, and simply do IsChecked="{Binding ShowPending}"

[Rob]

Although OneWay is the default for many properties, the IsChecked property is TwoWay by default. See Binding Overview