C#•2y ago

❔ WPF - Use command of viewmodel instead of item on click

Hi, I have a list of strings and display them as buttons. The list is held by a viewmodel and the viewmodel has a Command for the button click. Now, instead of creating an object for strings and add the Command to the items, I would like to have the Command at the viewmodel level.

  <Grid x:Name="LayoutRoot" Margin="5">
        <ItemsControl ItemsSource="{Binding Options}" Grid.Row="1">
            <ItemsControl.ItemsPanel>
                <ItemsPanelTemplate>
                    <StackPanel Orientation="Horizontal" HorizontalAlignment="Right" Margin="0,10,0,0" />
                </ItemsPanelTemplate>
            </ItemsControl.ItemsPanel>
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <Button Command="{Binding CloseDialogCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type vm:NotificationDialogViewModel}}}" CommandParameter="true" Content="{Binding }" MinWidth="75" Height="25" Margin="10,5,10,5" />
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </Grid>

  <Grid x:Name="LayoutRoot" Margin="5">
        <ItemsControl ItemsSource="{Binding Options}" Grid.Row="1">
            <ItemsControl.ItemsPanel>
                <ItemsPanelTemplate>
                    <StackPanel Orientation="Horizontal" HorizontalAlignment="Right" Margin="0,10,0,0" />
                </ItemsPanelTemplate>
            </ItemsControl.ItemsPanel>
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <Button Command="{Binding CloseDialogCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type vm:NotificationDialogViewModel}}}" CommandParameter="true" Content="{Binding }" MinWidth="75" Height="25" Margin="10,5,10,5" />
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </Grid>

  public class NotificationDialogViewModel : BindableBase, IDialogAware
  {
        private DelegateCommand<string> _closeDialogCommand;
        public DelegateCommand<string> CloseDialogCommand =>
            _closeDialogCommand ?? (_closeDialogCommand = new DelegateCommand<string>(CloseDialog));

        protected virtual void CloseDialog(string parameter)
        {
            ButtonResult result = ButtonResult.None;

            if (parameter?.ToLower() == "true")
                result = ButtonResult.OK;
            else if (parameter?.ToLower() == "false")
                result = ButtonResult.Cancel;

            RaiseRequestClose(new DialogResult(result, new DialogParameters($"parameter={parameter}")));
        }

  }

  public class NotificationDialogViewModel : BindableBase, IDialogAware
  {
        private DelegateCommand<string> _closeDialogCommand;
        public DelegateCommand<string> CloseDialogCommand =>
            _closeDialogCommand ?? (_closeDialogCommand = new DelegateCommand<string>(CloseDialog));

        protected virtual void CloseDialog(string parameter)
        {
            ButtonResult result = ButtonResult.None;

            if (parameter?.ToLower() == "true")
                result = ButtonResult.OK;
            else if (parameter?.ToLower() == "false")
                result = ButtonResult.Cancel;

            RaiseRequestClose(new DialogResult(result, new DialogParameters($"parameter={parameter}")));
        }

  }

6 Replies

DavaaronOP•2y ago

The error is:

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='Davaaron.BankOverview.ViewModels.Dialogs.NotificationDialogViewModel', AncestorLevel='1''. BindingExpression:Path=CloseDialogCommand; DataItem=null; target element is 'Button' (Name=''); target property is 'Command' (type 'ICommand')

HimmDawg•2y ago

Your AncestorType is a ViewModel. It's must always be a control tho

DavaaronOP•2y ago

Oh okay.. so I have to add some kind of event to the items (buttons) and then listen in the NotificationDialogViewModel.. alright

Klarth•2y ago

Your VM method is a bit weird given it basically has the result twice: RaiseRequestClose(new DialogResult(result, new DialogParameters($"parameter={parameter}"))); But besides that, your binding isn't correct. Indirect bindings go through controls first. I prefer ElementName bindings here because they're simpler to write.

<Grid x:Name="LayoutRoot" Margin="5">
    <ItemsControl x:Name="options" ItemsSource="{Binding Options}" Grid.Row="1">
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <StackPanel Orientation="Horizontal" HorizontalAlignment="Right" Margin="0,10,0,0" />
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>
        <ItemsControl.ItemTemplate>
            <DataTemplate>
                <Button Command="{Binding DataContext.CloseDialogCommand, ElementName=options}" CommandParameter="true" Content="{Binding}" MinWidth="75" Height="25" Margin="10,5,10,5" />
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>
</Grid>

<Grid x:Name="LayoutRoot" Margin="5">
    <ItemsControl x:Name="options" ItemsSource="{Binding Options}" Grid.Row="1">
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <StackPanel Orientation="Horizontal" HorizontalAlignment="Right" Margin="0,10,0,0" />
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>
        <ItemsControl.ItemTemplate>
            <DataTemplate>
                <Button Command="{Binding DataContext.CloseDialogCommand, ElementName=options}" CommandParameter="true" Content="{Binding}" MinWidth="75" Height="25" Margin="10,5,10,5" />
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>
</Grid>

So the Command binds to the ItemsControl, then into its DataContext (your VM...which I assume is the one you want?).

DavaaronOP•2y ago

Thank you very much, that worked!! 🙂

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ WPF - Use command of viewmodel instead of item on click