RadMultiColumnComboBox textbox not cleared when SelectedItem is null (MVVM)

[Roland]

How do I clear the RadMultiColumnComboBox text when the SelectedItem value it is bound to is NULL?  The ComboBox retains the value of the previous selection.

SelectedItem="{Binding SelectedPricedLineItem.ManufacturingGroup, Mode=TwoWay}"
DisplayMemberPath="DisplayValue"

When  SelectedPricedLineItem.ManufacturingGroup is NULL, the value displayed is is from the previous LineItem

Setting SelectedIndex to -1 is not an option since that would break MVVM.

[Dinko | Tech Support Engineer]

Hello Roland,

Thank you for the provided details.

I have tested your scenario, but I wasn't able to reproduce it. Can you confirm that your custom class is implementing the INotifyProperyChanged interface, and the property change method is called in the setter of custom property? If yes, may I ask you to share the set-up of the RadMultiColumnComboBox control? This way, I could try to build a project on my side and reproduce this.

Regards,
Dinko
Progress Telerik

[Roland]

Hi Dinko,

WPF R2 2021

I'm testing with your MultiColumnComboBox sample. Discovered that issue occurs when SelectionBoxesVisibility="Hidden" or when SelectionBoxesVisibility="Collapsed"

I want to dispaly text only; not selection boxes.

Maybe I'm encountering this issue...

https://feedback.telerik.com/wpf/1436800-radmulticolumncombobox-property-selectionboxesvisibility

Here's the Button code.

private void Button_Click(object sender, RoutedEventArgs e)
{
var vm = this.DataContext as ExampleViewModel;
vm.SelectedItem = null;
}

Thanks
Roland

[Dinko | Tech Support Engineer]

It seems that it is related to the behavior described in the mentioned feedback item. I will also include your scenario so that our development team will include it for fixing while working on the main one. As a workaround, you can get the RadWatermarkTextBox control which holds the text, and manually reset its Text property when the selection is cleared.

You can get the control in the loaded event of the MCCB.

RadWatermarkTextBox inputWatermarkTextBox = null;
private void Mccb_Loaded(object sender, RoutedEventArgs e)
{
    inputWatermarkTextBox = this.mccb.ChildrenOfType<RadWatermarkTextBox>().FirstOrDefault(x=>x.Name == "WatermarkTextBox");
}

private void RadButton_Click(object sender, RoutedEventArgs e)
{
    var vm = this.DataContext as MainViewModel;
    vm.VM.SelectedItem = null;
    if(inputWatermarkTextBox != null)
    {
        inputWatermarkTextBox.Text = string.Empty;
    }
}

I hope this approach will work for you.

[Roland]

Thank You Dinko. Your approach will work.