WPF DataGridCheckBoxColumn的更改行为null否

Question

I have DataGrid and List of objects. DataGrid is only to visualization. Now I want to change behavior of binding to DataGridCheckBoxColumn. I want three states like that:

null = unchecked
false = half checked
true = checked

Right now it looks like that:

null = half checked
false = unchecked
true = checked

I can change the logic inside code and treat null as false and false as null but for me better solution will be just different displaying. Binding looks like that

<DataGridCheckBoxColumn Header="SomeColumn" Binding="{Binding SomeProperty}" x:Name="SomeName" Visibility="Visible"/>

Answer 1

You could simply use a Converter like so:

public class CheckBoxConverter:IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value == null)
            return false;
        if ((bool) value)
            return true;
        return null;   //value is false
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        //Add the convert back if needed
        throw new NotImplementedException();
    }
}

and the Xaml will be :

 <DataGridCheckBoxColumn Header="SomeColumn" Binding="{Binding SomeProperty,Converter={StaticResource CheckBoxConverter}}" x:Name="SomeName" Visibility="Visible"/>

and don't forget to add the Converter to your window (or page) resources :

 <Window.Resources>
    <converters:CheckBoxConverter x:Key="CheckBoxConverter"/>
</Window.Resources>