.NET - How to Refresh Avalonia MenuFlyout ItemsSource When DataContext Changes in DataGrid Rows

Below is one workaround: instead of binding directly to MyUrlList from the MenuFlyout’s DataContext (which doesn’t update when the row’s DataContext changes), bind “up” to the SplitButton’s DataContext. For example, change

AXAMLCopied
<MenuFlyout ItemsSource="{Binding MyUrlList}">

to use a RelativeSource that finds the SplitButton and accesses its DataContext:

AXAMLCopied
<MenuFlyout ItemsSource="{Binding DataContext.MyUrlList, RelativeSource={RelativeSource AncestorType=SplitButton}}">

Because the SplitButton’s DataContext is refreshed with each new row, this binding ensures that the correct MyUrlList is used even if the row changes. This binding “hops” out of the MenuFlyout’s fixed DataContext into the parent (SplitButton) scope so that you always pick up the latest data.

Complete Example

Here’s your adjusted DataTemplate snippet:

AXAMLCopied
<DataTemplate DataType="model:MyModel">
  <SplitButton Content="My Url List" Command="{Binding OpenMyMainUrl}">
    <SplitButton.Flyout>
      <MenuFlyout ItemsSource="{Binding DataContext.MyUrlList, RelativeSource={RelativeSource AncestorType=SplitButton}}">
        <MenuFlyout.ItemContainerTheme>
          <ControlTheme TargetType="MenuItem" BasedOn="{StaticResource {x:Type MenuItem}}" x:DataType="model:Link">
            <Setter Property="Header" Value="{Binding MyText}"/>
            <Setter Property="Command" Value="{Binding OpenUrl}"/>
          </ControlTheme>
        </MenuFlyout.ItemContainerTheme>
      </MenuFlyout>
    </SplitButton.Flyout>
  </SplitButton>
</DataTemplate>

Explanation

• RelativeSource Binding: Using RelativeSource AncestorType=SplitButton lets the MenuFlyout bind to the SplitButton’s DataContext rather than its own.
• DataContext Refresh: Because the SplitButton resides in the DataGrid’s row and its DataContext is reset each time the row is updated or changed, MyUrlList will be refreshed.
• Use Case: This workaround circumvents the problem where the MenuFlyout “caches” its ItemsSource from the first loaded DataContext.

While this issue might indicate a bug in Avalonia, the above binding change is a practical workaround for your scenario.