WPF DataGrid - Creating a new custom Column

data-binding, datagrid, wpf

Solution

OK. Here is the complete code for a custom CheckBox column. It seems that, in order to have a control like a checkbox as a display (not editing) element in a DataGrid you have to make it hit-test-invisible. Or you can simply use a TextBlock to display some character that resembles a checkmark:

public class MyCheckBoxColumn : DataGridBoundColumn
{
    protected override FrameworkElement GenerateElement(DataGridCell cell, object dataItem)
    {
        var cb = new CheckBox() { IsHitTestVisible = false, HorizontalAlignment = HorizontalAlignment.Center, HorizontalContentAlignment = HorizontalAlignment.Center };
        var bb = this.Binding as Binding;
        var b = new Binding { Path = bb.Path, Source = dataItem, Mode = BindingMode.TwoWay };
        cb.SetBinding(ToggleButton.IsCheckedProperty, b);
        return cb;
//          var cb = new TextBlock() { TextAlignment = TextAlignment.Center, HorizontalAlignment = HorizontalAlignment.Center };
//          var bb = this.Binding as Binding;
//          var b = new Binding { Path = bb.Path, Source = dataItem, Mode = BindingMode.TwoWay, Converter = new MyBoolToMarkConverter() };
//          cb.SetBinding(TextBlock.TextProperty, b);
//          return cb;
    }

    protected override FrameworkElement GenerateEditingElement(DataGridCell cell, object dataItem)
    {
        var cb = new CheckBox() { HorizontalAlignment = HorizontalAlignment.Center, HorizontalContentAlignment = HorizontalAlignment.Center };
        var bb = this.Binding as Binding;
        var b = new Binding { Path = bb.Path, Source = dataItem, Mode = BindingMode.TwoWay };
        cb.SetBinding(ToggleButton.IsCheckedProperty, b);
        return cb;
    }

    protected override object PrepareCellForEdit(FrameworkElement editingElement, RoutedEventArgs editingEventArgs)
    {
        var cb = editingElement as CheckBox;
        if (cb != null) return cb.IsChecked;
        return false;
    }

    protected override void CancelCellEdit(FrameworkElement editingElement, object uneditedValue)
    {
        var cb = editingElement as CheckBox;
        if (cb != null) cb.IsChecked = (bool)uneditedValue;
    }

    protected override bool CommitCellEdit(FrameworkElement editingElement)
    {
        // The following 2 lines seem to help when sometimes the commit doesn't happen (for unknown to me reasons).
        //var cb = editingElement as CheckBox;
        //cb.IsChecked = cb.IsChecked;
        BindingExpression binding = editingElement.GetBindingExpression(ToggleButton.IsCheckedProperty);
        if (binding != null) binding.UpdateSource();
        return true;// base.CommitCellEdit(editingElement);
    }
}
//--------------------------------------------------------------------------------------------
public class MyBoolToMarkConverter : IValueConverter
{
    const string cTick = "■";

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value.GetType() != typeof(bool)) return "";
        bool val = (bool)value;
        return val ? cTick : "";
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value.GetType() != typeof(string)) return false;
        string val = (string)value;
        return val == cTick;
    }
}
//--------------------------------------------------------------------------------------------

Problem

Original source