How to Prevent Opening Popups for Read-only Popup Editors

Starting with version 1.2, you can use a popup editor's ShowPopupIfReadOnly property to prevent popups from being opened for read-only popup editors.

In earlier versions, you can control this behavior using the PopupEditor.PopupOpening event. The current topic provides more information on using this event.

When bound to read-only columns, in-place popup editors (DateEditor, ComboBoxEditor, MemoEditor, and so on) still allow their popups to be displayed. The PopupEditor.PopupOpening event fires just before a popup appears, allowing you to conditionally disable it — for example, when the editor is bound to a read-only column. You can handle this event for a specific in-place editor, or globally (to apply the logic to all popup editors in the application).

Disable Popups for a Specific Read-only Column

1. Associate an in-place editor with a grid column using the GridColumn.CellTemplate property.
2. Handle the editor's PopupEditor.PopupOpening event to perform actions when a popup is displayed for this editor.

In the following example, a grid column is associated with a DateEditor in-place editor. The DateEditor.PopupOpening event handler disables the editor's popup when the grid column is read-only.

<mxdg:GridColumn FieldName="BirthDate" Width="*" MinWidth="80">
    <mxdg:GridColumn.CellTemplate>
        <DataTemplate>
            <mxe:DateEditor x:Name="PART_Editor" PopupOpening="DateEditor_PopupOpening"/>
        </DataTemplate>
    </mxdg:GridColumn.CellTemplate>
</mxdg:GridColumn>

private void DateEditor_PopupOpening(object sender, OpeningPopupEventArgs e)
{
    e.Cancel = (sender as PopupEditor).ReadOnly;
}

Disable Popups for all Popup Editors Bound to Read-only Columns

You can use Class Handlers or the Behavior mechanism to process editors' events globally.

Use a Class Handler to Disable Popups for Read-only Editors Globally

Class Handlers in Avalonia enable event processing at the class level rather than the instance level. They allow you to attach event handlers to all instances of a control type without manually subscribing to each one.

The following example adds a class handler for the PopupEditor.PopupOpening event. This code affects all PopupEditor descendants.

public partial class MainWindow : MxWindow
{
    public MainWindow()
    {
        InitializeComponent();
        PopupEditor.PopupOpeningEvent.AddClassHandler<PopupEditor>(PopupEditor_PopupOpening);
    }

    private void PopupEditor_PopupOpening(object sender, OpeningPopupEventArgs e)
    {
        e.Cancel = (sender as PopupEditor).ReadOnly;
    }
}

Use the Behavior Mechanism to Disable Popups for Read-only Editors Globally

This approach requires the use of the Avalonia.Xaml.Interactivity package, which provides the Behavior pattern implementation for Avalonia UI. Behavior objects allow you to customize properties and subscribe to events for all instances of a given control type.

The following code creates a global Behavior object for all PopupEditor class instances. The Behavior object handles the PopupEditor.PopupOpening event to disable popups in read-only columns.

xmlns:mxe="https://schemas.eremexcontrols.net/avalonia/editors"
xmlns:behaviors="using:DemoCenter.Behaviors"

<UserControl.Styles>
    <Style Selector=":is(mxe|PopupEditor)">
        <Setter Property="Interaction.Behaviors">
            <Setter.Value>
                <BehaviorCollectionTemplate>
                    <BehaviorCollection>
                        <behaviors:PopupEditorReadOnlyPopupBehavior/>
                    </BehaviorCollection>
                </BehaviorCollectionTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</UserControl.Styles>

using Avalonia.Xaml.Interactivity;
using Eremex.AvaloniaUI.Controls.Editors;

namespace DemoCenter.Behaviors
{
    public class PopupEditorReadOnlyPopupBehavior : Behavior<PopupEditor>
    {
        protected override void OnAttached()
        {
            base.OnAttached();
            AssociatedObject.PopupOpening += AssociatedObject_PopupOpening;
        }

        protected override void OnDetachedFromVisualTree()
        {
            base.OnDetachedFromVisualTree();
            AssociatedObject.PopupOpening -= AssociatedObject_PopupOpening;
        }

        void AssociatedObject_PopupOpening(object sender, OpeningPopupEventArgs e)
        {
            e.Cancel = AssociatedObject.ReadOnly;
        }
    }
}