Use Int32 as DataMemberBinding of RadColorPickerColumn instead of Color

[Quang Khải]

In order to create a Custom editor with RadGridView by following a guide at: Create Custom Editor with RadGridView

It looks OK, but I would change the DataMemberBinding to Int32 instead of System.Windows.Media.Color, because System.Windows.Media.Color belongs to View class I don't really want to use it in my ViewModel. The converter looks like:

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
      int num= System.Convert.ToInt32(value);
      Color color;
      byte[] bytes = BitConverter.GetBytes(num);
      color = Color.FromArgb(bytes[3], bytes[2], bytes[1], bytes[0]);
      return new SolidColorBrush(color);
 }

[Quang Khải]

To be clear, the exception thrown by the picker control internally.

System.Windows.Data Error: 8 : Cannot save value from target back to source. BindingExpression:Path=Color; DataItem='MyVM' (HashCode=7290323); target element is 'CustomColorPicker' (Name=''); target property is 'SelectedColor' (type 'Color') ArgumentException:'System.ArgumentException: Object of type 'System.Windows.Media.Color' cannot be converted to type 'System.Int32'.
   at System.RuntimeType.TryChangeType(Object value, Binder binder, CultureInfo culture, Boolean needsSpecialCast)
   at System.Reflection.MethodBase.CheckArguments(Object[] parameters, Binder binder, BindingFlags invokeAttr, CultureInfo culture, Signature sig)
   at System.Reflection.RuntimeMethodInfo.InvokeArgumentsCheck(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.RuntimePropertyInfo.SetValue(Object obj, Object value, Object[] index)
   at MS.Internal.Data.PropertyPathWorker.SetValue(Object item, Object value)
   at System.Windows.Data.BindingExpression.UpdateSource(Object value)'

[Dinko | Tech Support Engineer]

Hello Jacky Phan,

In case you want to change the example in the Create Custom Editor with RadGridView to use int instead of color you can modify the CreateValueBinding() method (from the article). You can set the Converter property of the binding. This way when you are in edit mode and choose a color the ConvertBack() method of the ColorToBrushConverter will be called. To workaround the error you can return int instead of color. Check the following code snippets.

private Binding CreateValueBinding()
{
    Binding valueBinding = new Binding();
    valueBinding.Mode = BindingMode.TwoWay;
    valueBinding.Converter = new ColorToBrushConverter();
    valueBinding.NotifyOnValidationError = true;
    valueBinding.ValidatesOnExceptions = true;
    valueBinding.UpdateSourceTrigger = UpdateSourceTrigger.Explicit;
    valueBinding.Path = new PropertyPath(this.DataMemberBinding.Path.Path);
    return valueBinding;
}

public class ColorToBrushConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {

        int num = System.Convert.ToInt32(value);
        Color color;
        byte[] bytes = BitConverter.GetBytes(num);
        color = Color.FromArgb(bytes[3], bytes[2], bytes[1], bytes[0]);
        return new SolidColorBrush(color);
        //var color = (Color)value;
        //if (color != null)
        //{
        //    return new SolidColorBrush(color);
        //}
        //return value;
    }
    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        string colorcode = value.ToString();
        int argb = Int32.Parse(colorcode.Replace("#", ""), NumberStyles.HexNumber);
        return argb;
    }
}

Give this approach a try and let me know if it works for you.

Regards,
Dinko
Progress Telerik

[Quang Khải]

Thanks for the answer, it works properly.

It seems we have 2 converters, one for cellcontrol, one for value binding.