OK - So I’ve got a WPF DataGrid, with a DataGridTemplateColumn. The DataTemplate is a plane TextBox. When I tab through the cells, I want to select the text in the TextBox. And when I click the text in the TextBox, I also want to select it. That proved more difficult than I expected.

But hacking and slashing from this blog

http://andora.us/blog/2011/06/09/wpf-textbox-select-all-on-focus/

and this answer

http://stackoverflow.com/questions/1104164/wpf-datagridtemplatecolumn-am-i-missing-something

I came up with a solution. Although not strictly MVVM, I still think it falls under that design pattern. All View related stuff is still handled in the View.

Anyway - First of all. when you tab through the cells the first tab stop is the border of the cell, and the second is the actual TextBox.

Secondly, In WPF, the default behavior of the TextBox on focus is to put the cursor where it was the last time the TextBox had lost focus or if it hasn’t had focus yet, at the beginning.

The first problem I solved by by using the answer from stackoverflow:

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

The second by following Andora block. So the hole XAML 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>
</DataGrid>

And the code-behind like this:

private void TextBox_GotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
	try
	{
		((TextBox)sender).SelectAll();
	}
	catch { }
}

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 { }
}

As always, feel free to comment, or ask.

 It took me some time to find a solution to this problem, but here is a working solution.

 I wanted to be able to drag 'n drop WPF DataGrid rows in MVVM, and although this solution is not strickly MVVM, I still think that it fits nicely in that design patten. All GUI it handled within the view, and all logic in the ViewModel.

 I found a good starting point for this solution somewhere, but again unfortunately I have forgotten where. I think it was on codeproject. My sincere apologies to the author.

 The follwing goes into the UserControl code behind:

using Baltz.ViewModel;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace Baltz.View
{
    /// <summary>
    /// Interaction logic for DataGridDraggableRowView.xaml
    /// </summary>
    public partial class DataGridDraggableRowView : UserControl
    {
        public DataGridDraggableRowView()
        {
            InitializeComponent();
        }

        #region Static Methods
        private static T FindVisualParent<T>(UIElement element) where T : UIElement
        {
            var parent = element;
            while (parent != null)
            {
                var correctlyTyped = parent as T;
                if (correctlyTyped != null)
                {
                    return correctlyTyped;
                }

                parent = VisualTreeHelper.GetParent(parent) as UIElement;
            }
            return null;
        }
        #endregion

        #region Fields
        private int _originalIndex;
        private DataGridRow _oldRow;
        private DataGridDraggableRowItem _targetItem;
        private DataGridDraggableRowViewModel _viewModel;
        #endregion Fields

        #region Event Handlers
        /// <summary>
        /// Updates the grid as a drag progresses
        /// </summary>
        private void OnMainGridCheckDropTarget(object sender, DragEventArgs e)
        {
            var row = FindVisualParent<DataGridRow>(e.OriginalSource as UIElement);

            // Set the DragDropEffects 
            if ((row == null) || !(row.Item is DataGridDraggableRowItem))
            {
                e.Effects = DragDropEffects.None;
            }
            else
            {
                var currentIndex = row.GetIndex();

                // Erase old drop-line
                if (_oldRow != null)
                    _oldRow.BorderThickness = new Thickness(0);

                // Draw new drop-line
                var direction = (currentIndex - _originalIndex);
                if (direction < 0)
                    row.BorderThickness = new Thickness(0, 2, 0, 0);
                else if (direction > 0)
                    row.BorderThickness = new Thickness(0, 0, 0, 2);
                row.BorderBrush = new SolidColorBrush(Color.FromArgb(0xFF, 0x00, 0x9C, 0xDD));
                // Reset old row
                _oldRow = row;
            }
        }

        /// <summary>
        /// Gets the view model from the data Context and assigns it to a member variable.
        /// </summary>
        private void OnMainGridDataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            _viewModel = (DataGridDraggableRowViewModel)this.DataContext;
        }

        /// <summary>
        /// Process a row drop on the DataGrid.
        /// </summary>
        private void OnMainGridDrop(object sender, DragEventArgs e)
        {
            e.Effects = DragDropEffects.None;
            e.Handled = true;

            // Verify that this is a valid drop and then store the drop target
            var row = FindVisualParent<DataGridRow>(e.OriginalSource as UIElement);
            if (row != null)
            {
                _targetItem = row.Item as DataGridDraggableRowItem;
                if (_targetItem != null)
                {
                    e.Effects = DragDropEffects.Move;
                }
            }

            // Erase last drop-line
            if (_oldRow != null)
                _oldRow.BorderThickness = new Thickness(0, 0, 0, 0);
        }

        /// <summary>
        /// Processes a drag in the main grid.
        /// </summary>
        private void OnMainGridMouseMove(object sender, MouseEventArgs e)
        {
            // Exit if left mouse button aren't pressed
            if (e.LeftButton != MouseButtonState.Pressed)
                return;

            // Find the row the mouse button was pressed on
            var row = FindVisualParent<DataGridRow>(e.OriginalSource as FrameworkElement);
            _originalIndex = row.GetIndex();

            // If the row was already selected, begin drag
            if ((row != null) && row.IsSelected)
            {
                // Get the grocery item represented by the selected row
                var selectedItem = (DataGridDraggableRowItem)row.Item;
                var finalDropEffect = DragDrop.DoDragDrop(row, selectedItem, DragDropEffects.Move);
                if ((finalDropEffect == DragDropEffects.Move) && (_targetItem != null))
                {
                    /* A drop was accepted. Determine the index of the item being 
                     * dragged and the drop location. If they are different, then 
                     * move the selectedItem to the new location. */

                    // Move the dragged item to its drop position
                    var oldIndex = _viewModel.Rows.IndexOf(selectedItem);
                    var newIndex = _viewModel.Rows.IndexOf(_targetItem);
                    if (oldIndex != newIndex)
                        _viewModel.Rows.Move(oldIndex, newIndex);
                    _targetItem = null;
                }
            }
        }
        #endregion
    }
}

A side note: This style is based on a style posted in another post

<ResourceDictionary x:Class="Ellab.Main.Settings.SettingsWindow.View.Styles.DraggableDataGridStyle"
                    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
                    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
                    mc:Ignorable="d">
    <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary Source="DataGridStyle.xaml"/>
    </ResourceDictionary.MergedDictionaries>
    <Style x:Key="DefaultDraggableDataGrid" BasedOn="{StaticResource DefaultSettingsDataGrid}" TargetType="{x:Type DataGrid}">
        <Setter Property="HeadersVisibility" Value="Column"/>
        <Setter Property="AllowDrop" Value="True"/>
    </Style>
    <Style TargetType="{x:Type DataGridCell}">
        <Style.Resources>
            <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="#FF009CDD" />
            <SolidColorBrush x:Key="{x:Static SystemColors.ControlBrushKey}" Color="#FF009CDD" />
            <SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}" Color="Black" />
            <SolidColorBrush x:Key="{x:Static SystemColors.ControlTextBrushKey}" Color="Black" />
        </Style.Resources>
    </Style>
</ResourceDictionary>

And this is the complete View - most of it isn't relevant for the dragable rows.

<UserControl x:Class="foo.View.barDataGridDraggableRowView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <UserControl.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="Styles/DraggableDataGridStyle.xaml"/>
                <ResourceDictionary Source="Styles/ContentPresenterStyle.xaml"/>
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </UserControl.Resources>
    <StackPanel Orientation="Vertical" Background="Transparent">
        <ContentPresenter Content="{Binding Path=HeaderButton}" Style="{StaticResource DefaultContentPresenter}"/>
        <StackPanel Orientation="Vertical" Background="Transparent" Visibility="{Binding Path=IsExpanded}">
            <DataGrid ItemsSource="{Binding Path=Rows}"
                  MouseMove="OnMainGridMouseMove"
                  DragEnter="OnMainGridCheckDropTarget"
                  DragLeave="OnMainGridCheckDropTarget"
                  DragOver="OnMainGridCheckDropTarget"
                  Drop="OnMainGridDrop" 
                  DataContextChanged="OnMainGridDataContextChanged"
                  Style="{StaticResource DefaultDraggableDataGrid}">
                <DataGrid.Columns>
                    <DataGridTemplateColumn IsReadOnly="True" Width="20">
                        <DataGridTemplateColumn.CellTemplate>
                            <DataTemplate>
                                <Image Source="../../Resources/DragDrop.png" Stretch="Fill" Opacity="{Binding Opacity}"/>
                            </DataTemplate>
                        </DataGridTemplateColumn.CellTemplate>
                    </DataGridTemplateColumn>
                    <DataGridTemplateColumn IsReadOnly="True">
                        <DataGridTemplateColumn.Header>
                            <TextBlock Text="{Binding DataContext.EnabledColumnHeader, RelativeSource={RelativeSource AncestorType=DataGrid}}" MaxWidth="65" TextWrapping="WrapWithOverflow" TextTrimming="CharacterEllipsis">
                                <TextBlock.LayoutTransform>
                                    <TransformGroup>
                                        <RotateTransform Angle="90" />
                                        <ScaleTransform ScaleX="-1" ScaleY="-1"/>
                                    </TransformGroup>
                                </TextBlock.LayoutTransform>
                            </TextBlock>
                        </DataGridTemplateColumn.Header>
                        <DataGridTemplateColumn.CellTemplate>
                            <DataTemplate>
                                <CheckBox HorizontalAlignment="Center" VerticalAlignment="Center" IsChecked="{Binding EnabledChecked, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" Opacity="{Binding Opacity}" IsEnabled="{Binding Enable}"/>
                            </DataTemplate>
                        </DataGridTemplateColumn.CellTemplate>
                    </DataGridTemplateColumn>
                    <DataGridTemplateColumn IsReadOnly="True">
                        <DataGridTemplateColumn.Header>
                            <TextBlock Text="{Binding DataContext.WizardColumnHeader, RelativeSource={RelativeSource AncestorType=DataGrid}}" MaxWidth="65" TextWrapping="WrapWithOverflow" TextTrimming="CharacterEllipsis">
                                <TextBlock.LayoutTransform>
                                    <TransformGroup>
                                        <RotateTransform Angle="90" />
                                        <ScaleTransform ScaleX="-1" ScaleY="-1"/>
                                    </TransformGroup>
                                </TextBlock.LayoutTransform>
                            </TextBlock>
                        </DataGridTemplateColumn.Header>
                        <DataGridTemplateColumn.CellTemplate>
                            <DataTemplate>
                                <CheckBox HorizontalAlignment="Center" VerticalAlignment="Center" IsChecked="{Binding WizardChecked, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" Opacity="{Binding Opacity}" IsEnabled="{Binding Enable}" Visibility="{Binding WizardVisible}"/>
                            </DataTemplate>
                        </DataGridTemplateColumn.CellTemplate>
                    </DataGridTemplateColumn>
                    <DataGridTemplateColumn IsReadOnly="True" Width="*">
                        <DataGridTemplateColumn.Header>
                            <TextBlock Text="{Binding DataContext.TextColumnHeader, RelativeSource={RelativeSource AncestorType=DataGrid}}" TextWrapping="WrapWithOverflow" TextTrimming="CharacterEllipsis" VerticalAlignment="Bottom"/>
                        </DataGridTemplateColumn.Header>
                        <DataGridTemplateColumn.CellTemplate>
                            <DataTemplate>
                                <TextBlock Text="{Binding Text}" HorizontalAlignment="Left" VerticalAlignment="Center" Opacity="{Binding Opacity}" IsEnabled="{Binding Enable}"/>
                            </DataTemplate>
                        </DataGridTemplateColumn.CellTemplate>
                    </DataGridTemplateColumn>
                    <DataGridTemplateColumn IsReadOnly="True" Width="40">
                        <DataGridTemplateColumn.CellTemplate>
                            <DataTemplate>
                                <Image Source="{Binding TileImage}" Opacity="{Binding Opacity}"/>
                            </DataTemplate>
                        </DataGridTemplateColumn.CellTemplate>
                    </DataGridTemplateColumn>
                </DataGrid.Columns>
            </DataGrid>
            <ContentPresenter Content="{Binding Path=TilesRemainingText}"/>
        </StackPanel>
    </StackPanel>
</UserControl>

As always, feel free to comment, or ask.