wpftoolkit/ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/WatermarkTextBox/Implementation/WatermarkTextBox.cs

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

namespace Microsoft.Windows.Controls
{
    public class WatermarkTextBox : TextBox
    {
        #region Properties

        #region SelectAllOnGotFocus

        public static readonly DependencyProperty SelectAllOnGotFocusProperty = DependencyProperty.Register("SelectAllOnGotFocus", typeof(bool), typeof(WatermarkTextBox), new PropertyMetadata(false));
        public bool SelectAllOnGotFocus
        {
            get { return (bool)GetValue(SelectAllOnGotFocusProperty); }
            set { SetValue(SelectAllOnGotFocusProperty, value); }
        }

        #endregion //SelectAllOnGotFocus

        #region Watermark

        public static readonly DependencyProperty WatermarkProperty = DependencyProperty.Register("Watermark", typeof(object), typeof(WatermarkTextBox), new UIPropertyMetadata(null));
        public object Watermark
        {
            get { return (object)GetValue(WatermarkProperty); }
            set { SetValue(WatermarkProperty, value); }
        }

        #endregion //Watermark

        #region WatermarkTemplate

        public static readonly DependencyProperty WatermarkTemplateProperty = DependencyProperty.Register("WatermarkTemplate", typeof(DataTemplate), typeof(WatermarkTextBox), new UIPropertyMetadata(null));
        public DataTemplate WatermarkTemplate
        {
            get { return (DataTemplate)GetValue(WatermarkTemplateProperty); }
            set { SetValue(WatermarkTemplateProperty, value); }
        }       

        #endregion //WatermarkTemplate

        #endregion //Properties

        #region Constructors

        static WatermarkTextBox()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(WatermarkTextBox), new FrameworkPropertyMetadata(typeof(WatermarkTextBox)));
        }

        #endregion //Constructors

        #region Base Class Overrides

        protected override void OnGotKeyboardFocus(KeyboardFocusChangedEventArgs e)
        {
            base.OnGotKeyboardFocus(e);

            if (SelectAllOnGotFocus)
                SelectAll();
        }

        protected override void OnPreviewMouseLeftButtonDown(MouseButtonEventArgs e)
        {
            if (!IsKeyboardFocused && SelectAllOnGotFocus)
            {
                e.Handled = true;
                Focus();
            }

            base.OnPreviewMouseLeftButtonDown(e);
        }

        #endregion //Base Class Overrides
    }
}