Automatic editing of WPF datagrid content when datagrid-cell gets focus

Question

I have a datagrid in WPF with a DataGridTextColum and a DataGridTemplateColum.

<DataGridTextColumn Width="4*" IsReadOnly="True" x:Name="dataGridColumnDescription" 
Header="Description" Binding="{Binding Description}">
</DataGridTextColumn>

<DataGridTemplateColumn CellStyle="{StaticResource CellEditing}" IsReadOnly="False" Width="*" Header="Value" 
CellEditingTemplateSelector="{StaticResource myCellEditingTemplateSelectorValue}" 
CellTemplateSelector="{StaticResource myCellTemplateSelectorValue}">
</DataGridTemplateColumn>

The CellTemplateSelectors return a DataTemplate with a TextBlock for the the Celltemplate resp. a TextBox for CellEditing!

<DataTemplate x:Key="dGridStringValueTemplate">
    <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center" Text="{Binding Path=Value}"/>
</DataTemplate>

<DataTemplate x:Key="dGridStringValueTemplateEditing">
    <TextBox TextAlignment="Center" VerticalAlignment="Center" VerticalContentAlignment="Center" HorizontalContentAlignment="Center" BorderThickness="1" Text="{Binding Path=Value, UpdateSourceTrigger=LostFocus}"/>
</DataTemplate>

Now I want to automatically Focus the TextBox when the DataGridCell gets the focus. The user should be able to edit the TextBox content without doubleclicking the cell.

I found this article:

DataGrid Tips & Tricks: Single-Click Editing where I can get the Current DataGridCell, but how can I access the content to give the Textbox the focus to edit the content?

This is my style:

<Style x:Key="CellEditing" TargetType="{x:Type DataGridCell}">
    <EventSetter Event="PreviewMouseLeftButtonDown" Handler="myDataGridMain_PreviewMouseLeftButtonDown"></EventSetter>
</Style>

This is my event handler:

private void myDataGridMain_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    DataGridCell cell = sender as DataGridCell;     // cell ist not null

    DataGridTemplateColumn col = cell.Column as DataGridTemplateColumn; //col is not null

    DataTemplate template = col.CellTemplate;  //this is null
}

How can I get the textbox with that event handler?

Answer 1

This seems to work :

    <DataGrid ItemsSource="{Binding Items}" AutoGenerateColumns="False">
        <DataGrid.Columns>
            <DataGridTemplateColumn>
                <DataGridTemplateColumn.CellEditingTemplate>
                    <DataTemplate>
                        <TextBox  FocusManager.FocusedElement="{Binding RelativeSource={RelativeSource Self}}"></TextBox>
                    </DataTemplate>
                </DataGridTemplateColumn.CellEditingTemplate>
            </DataGridTemplateColumn>
        </DataGrid.Columns>
    </DataGrid>

Answer 2

This approach works for me. It uses the fact that the DataGrid will always create a new instance of the template when the editing starts:

<DataGridTemplateColumn.CellEditingTemplate>
    <DataTemplate>
        <TextBox Text="{Binding MyProperty}" 
                 Loaded="TextBox_Loaded"></TextBox>
    </DataTemplate>
</DataGridTemplateColumn.CellEditingTemplate>

and in the code behind:

private void TextBox_Loaded(object sender, RoutedEventArgs e)
{
    ((TextBox)sender).Focus();
    ((TextBox)sender).SelectAll();
}

As an added bonus, it also selects all text in the cell. It should work no matter how you enter the editing mode (double click, single click, pressing F2)