Separate version

Net40/HandyControl_Net40/Controls/Input/WatermarkTextBox.cs

@@ -0,0 +1,77 @@
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Data;
+
+namespace HandyControl.Controls
+{
+    [TemplatePart(Name = ElementContentName, Type = typeof(ContentControl))]
+    public class WatermarkTextBox : TextBox
+    {
+        #region Constants
+
+        private const string ElementContentName = "PART_Watermark";
+
+        #endregion Constants
+
+        #region Data
+
+        private ContentControl _elementContent;
+
+        #endregion Data
+
+        #region Public Properties
+
+        #region Watermark
+
+        public static readonly DependencyProperty WatermarkProperty = DependencyProperty.Register(
+            "Watermark", typeof(object), typeof(WatermarkTextBox), new PropertyMetadata(default(object), OnWatermarkChanged));
+
+        private static void OnWatermarkChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            var ctl = (WatermarkTextBox) d;
+            ctl.OnWatermarkChanged();
+        }
+
+        public object Watermark
+        {
+            get => GetValue(WatermarkProperty);
+            set => SetValue(WatermarkProperty, value);
+        }
+
+        #endregion Watermark
+
+        #endregion Public Properties
+
+        public override void OnApplyTemplate()
+        {
+            base.OnApplyTemplate();
+
+            _elementContent = GetTemplateChild(ElementContentName) as ContentControl;
+            _elementContent?.SetBinding(ContentControl.ContentProperty, new Binding(WatermarkProperty.Name) {Source = this});
+
+            OnWatermarkChanged();
+        }
+
+        private void OnWatermarkChanged()
+        {
+            if (_elementContent == null) return;
+            if (Watermark is Control watermarkControl)
+            {
+                watermarkControl.IsTabStop = false;
+                watermarkControl.IsHitTestVisible = false;
+            }
+        }
+
+        protected override void OnGotFocus(RoutedEventArgs e)
+        {
+            base.OnGotFocus(e);
+            if (IsEnabled)
+            {
+                if (!string.IsNullOrEmpty(Text))
+                {
+                    Select(0, Text.Length);
+                }
+            }
+        }
+    }
+}