WPF DataGridTemplateColumn. Am I missing something

Question

     <data:DataGridTemplateColumn Header="Name">
        <data:DataGridTemplateColumn.CellTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Name}">
            </DataTemplate>
        </data:DataGridTemplateColumn.CellTemplate> 
        <data:DataGridTemplateColumn.CellEditingTemplate>
            <DataTemplate>
                <TextBox Text="{Binding Name}">
            </DataTemplate>
        </data:DataGridTemplateColumn.CellEditingTemplate> 
    </data:DataGridTemplateColumn>              

It's clear example of Template column, right? What could be wrong with that? So, here is the thing - when a user navigates through DataGrid with hitting TAB-key, it needs to hit the TAB twice(!) to be able to edit text in TextBox. How could I make it editable as soon as the user gets the column focus, I mean even if he just starts typing?

Ok. I found a way - into Grid.KeyUp() I put the code below:

 if (Grid.CurrentColumn.Header.ToString() == "UserName")
        {
            if (e.Key != Key.Escape) 
            {
                Grid.BeginEdit();

                // Simply send another TAB press
                if (Keyboard.FocusedElement is Microsoft.Windows.Controls.DataGridCell)
                {
                    var keyEvt = new KeyEventArgs(Keyboard.PrimaryDevice, Keyboard.PrimaryDevice.ActiveSource, 0, Key.Tab) { RoutedEvent = Keyboard.KeyDownEvent };
                    InputManager.Current.ProcessInput(keyEvt);
                }
            }
        } 

Answer 1

your issue stems from the fact that each cell puts its editor in a content control which first receives focus, then you have to tab once again to the editor. If you have a look at the code for DataGridTemplateColumn in the GenerateEditingElement method it calls a method LoadTemplateContent which does this:

private FrameworkElement LoadTemplateContent(bool isEditing, object dataItem, DataGridCell cell)
{
    DataTemplate template = ChooseCellTemplate(isEditing);
    DataTemplateSelector templateSelector = ChooseCellTemplateSelector(isEditing);
    if (template != null || templateSelector != null)
    {
        ContentPresenter contentPresenter = new ContentPresenter();
        BindingOperations.SetBinding(contentPresenter, ContentPresenter.ContentProperty, new Binding());
        contentPresenter.ContentTemplate = template;
        contentPresenter.ContentTemplateSelector = templateSelector;
        return contentPresenter;
    }

    return null;
}

see how it creates a new content presenter to put the template in. Other people have dealt with this problem in a variety of ways, I derive my own column type to deal with this stuff. (so i dont create an extra element or set the content presenter to not receive focus) In this example they are using focus manager to deal with the same issue (i havent tested this code)

<tk:DataGridTemplateColumn.CellEditingTemplate>
   <DataTemplate>
      <Grid FocusManager.FocusedElement="{Binding ElementName=txt1}">
         <TextBox Name="txt1" Text="{Binding XPath=@ISBN}" 
                  BorderThickness="0" GotFocus="TextBox_GotFocus"/>
      </Grid>
   </DataTemplate>
</tk:DataGridTemplateColumn.CellEditingTemplate>

If you have a user control as your editor then you can use the pattern with the focus manager or use an event handler for the OnLoaded event.

Answer 2

Here is my approach. Its very close to @Nalin Jayasuriya answer, but I didn't want to create a style. Also this solution selects the text in the TextBox. Anyway - the XAML for the hole DataGrid looks like this.

<DataGrid Name="TextBlockDataGrid" ItemsSource="{Binding Path=Rows}" Style="{StaticResource DefaultSettingsDataGrid}">
<DataGrid.Columns>
    <DataGridTextColumn Binding="{Binding Text}" IsReadOnly="True"/>
    <DataGridTemplateColumn Width="*">
        <DataGridTemplateColumn.CellStyle>
            <Style TargetType="{x:Type DataGridCell}">
                <Setter Property="KeyboardNavigation.IsTabStop" Value="False"/>
            </Style>
        </DataGridTemplateColumn.CellStyle>
        <DataGridTemplateColumn.CellTemplate>
            <DataTemplate>
                <Border BorderThickness="{Binding ErrorBorderThickness}" BorderBrush="{Binding ErrorBorderBrush}">
                    <TextBox Text="{Binding UserText, Mode=TwoWay, UpdateSourceTrigger=LostFocus}"
                             HorizontalAlignment="Right"
                             GotKeyboardFocus="TextBox_GotKeyboardFocus"
                             PreviewMouseDown="TextBox_PreviewMouseDown"
                             Style="{StaticResource DefaultTextBox}"/>
                </Border>
            </DataTemplate>
        </DataGridTemplateColumn.CellTemplate>
    </DataGridTemplateColumn>
</DataGrid.Columns>

And the code-behind.

private void TextBox_GotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
    try
    {
        ((TextBox)sender).SelectAll();
    }
    catch (Exception ex) { GlobalDebug.debugForm.WriteText(ex); }
}

private void TextBox_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
    try
    {
        // If its a triple click, select all text for the user.
        if (e.ClickCount == 3)
        {
            ((TextBox)sender).SelectAll();
            return;
        }

        // Find the TextBox
        DependencyObject parent = e.OriginalSource as UIElement;
        while (parent != null && !(parent is TextBox))
        {
            parent = System.Windows.Media.VisualTreeHelper.GetParent(parent);
        }

        if (parent != null)
        {
            if (parent is TextBox)
            {
                var textBox = (TextBox)parent;
                if (!textBox.IsKeyboardFocusWithin)
                {
                    // If the text box is not yet focussed, give it the focus and
                    // stop further processing of this click event.
                    textBox.Focus();
                    e.Handled = true;
                }
            }
        }
    }
    catch (Exception ex) { GlobalDebug.debugForm.WriteText(ex); }
}

For a more info, have a look at my blog: http://blog.baltz.dk/post/2014/11/28/WPF-DataGrid-set-focus-and-mark-text

Answer 3

The issue that you faced is that the control (e.g. TextBox) within the DataGridTemplateColumn is contained within a DataGridCell. By default the DataGridCell has tab-stop functionality. Thus the reason for having to hit TAB twice to get focus to your TextBox control. The solution is to disable the tab-stop functionality for the DataGridCell. This can be done via a style for the DataGridCell.

Here's the solution:

<Style TargetType="{x:Type DataGridCell}">
     <Setter Property="KeyboardNavigation.IsTabStop" Value="False" />
</Style>

Answer 4

My approach is to use a TriggerAction which sets the focus to the template element you want when it loads.

The trigger is very simple:

public class TakeFocusAndSelectTextOnVisibleBehavior : TriggerAction<TextBox>
{
    protected override void Invoke(object parameter)
    {
        Dispatcher.BeginInvoke(
            DispatcherPriority.Loaded,
            new Action(() =>
            {
                AssociatedObject.Focus();
                AssociatedObject.SelectAll();
            }));
    }
}

The DataTemplate looks like this:

<DataTemplate>
    <TextBox Text="{Binding Path=Price, Mode=TwoWay}"
                MinHeight="0"
                Padding="1,0"
                Height="20">
        <Interactivity:Interaction.Triggers>
            <Interactivity:EventTrigger EventName="Loaded">
                <Behaviors:TakeFocusAndSelectTextOnVisibleBehavior />
            </Interactivity:EventTrigger>
        </Interactivity:Interaction.Triggers>
    </TextBox>
</DataTemplate>

You can write other triggers for other element types.