一、简单设置水印TextBox控件，废话不多说看代码：

这里的style可以单独提出来，方便多处使用。

设置之后的效果如下：

二、扩展增强TextBox

有的时候会碰到TextBox里面需要添加按钮，或者TextBox需要设置圆角。这个时候就需要添加自定义控件，添加依赖属性来扩展功能了。

2.1 添加自定义控件TextBoxEx

代码如下：

public class TextBoxEx : TextBox    {        static TextBoxEx()        {            DefaultStyleKeyProperty.OverrideMetadata(typeof(TextBoxEx), new FrameworkPropertyMetadata(typeof(TextBoxEx)));        }        public TextBoxEx()        {            CommandBindings.Add(new CommandBinding(SearchClickCommand, delegate            {                SearchClick?.Invoke(this, null);            }));        }        public static RoutedUICommand SearchClickCommand = new RoutedUICommand(nameof(SearchClickCommand), nameof(SearchClickCommand), typeof(RoutedUICommand));        public event EventHandler SearchClick;        public string WaterMark        {            get { return (string)GetValue(WaterMarkProperty); }            set { SetValue(WaterMarkProperty, value); }        }        public static readonly DependencyProperty WaterMarkProperty =            DependencyProperty.Register("WaterMark", typeof(string), typeof(TextBoxEx), new PropertyMetadata(null));        public ImageSource Icon        {            get { return (ImageSource)GetValue(IconProperty); }            set { SetValue(IconProperty, value); }        }        public static readonly DependencyProperty IconProperty =            DependencyProperty.Register("Icon", typeof(ImageSource), typeof(TextBoxEx), new PropertyMetadata(null));        public new Brush BorderBrush        {            get { return (Brush)GetValue(BorderBrushProperty); }            set { SetValue(BorderBrushProperty, value); }        }        public static readonly new DependencyProperty BorderBrushProperty =            DependencyProperty.Register("BorderBrush", typeof(Brush), typeof(TextBoxEx), new PropertyMetadata(new SolidColorBrush(Color.FromRgb(234,234,234))));        public Brush MouseOverBorderBrush        {            get { return (Brush)GetValue(MouseOverBorderBrushProperty); }            set { SetValue(MouseOverBorderBrushProperty, value); }        }        public static readonly DependencyProperty MouseOverBorderBrushProperty =            DependencyProperty.Register("MouseOverBorderBrush", typeof(Brush), typeof(TextBoxEx), new PropertyMetadata(new SolidColorBrush(Color.FromRgb(79,173,216))));        public new Brush Background        {            get { return (Brush)GetValue(BackgroundProperty); }            set { SetValue(BackgroundProperty, value); }        }        public static readonly new DependencyProperty BackgroundProperty =            DependencyProperty.Register("Background", typeof(Brush), typeof(TextBoxEx), new PropertyMetadata(new SolidColorBrush(Color.FromRgb(106,103,90))));        public Brush MouseOverBackground        {            get { return (Brush)GetValue(MouseOverBackgroundProperty); }            set { SetValue(MouseOverBackgroundProperty, value); }        }        public static readonly DependencyProperty MouseOverBackgroundProperty =            DependencyProperty.Register("MouseOverBackground", typeof(Brush), typeof(TextBoxEx), new PropertyMetadata(Color.FromRgb(106,103,90)));        public CornerRadius CornerRadius        {            get { return (CornerRadius)GetValue(CornerRadiusProperty); }            set { SetValue(CornerRadiusProperty, value); }        }        public static readonly DependencyProperty CornerRadiusProperty =            DependencyProperty.Register("CornerRadius", typeof(CornerRadius), typeof(TextBoxEx), new PropertyMetadata(new CornerRadius(0)));        public IconDirection IconDirection        {            get { return (IconDirection)GetValue(IconDirectionProperty); }            set { SetValue(IconDirectionProperty, value); }        }        public static readonly DependencyProperty IconDirectionProperty =            DependencyProperty.Register("IconDirection", typeof(IconDirection), typeof(TextBoxEx), new PropertyMetadata(IconDirection.Right));    }    public enum IconDirection    {        Left,        Right    }

 

2.2 设置TextBoxEx样式

这里面使用了一个转换器cornerRadiusToThickness，转换器的作用是当TextBox设置了圆角之后，保证TextBox里的内容不溢出圆角。WPF转换器的使用大家可以百度。

转换器的内容如下：

public class CornerRadiusToThickness : IValueConverter    {        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)        {            Thickness result = new Thickness(0);            if (value is CornerRadius)            {                var tem = (CornerRadius)value;                result = new Thickness(tem.TopLeft, 0, tem.TopRight, 0);            }            return result;        }        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)        {            throw new NotImplementedException();        }    }

另外为了触发TextBox按钮的单击事件，添加了这个两个dll文件引用，Microsoft.Expression.Interactions.dll和System.Windows.Interactivity.dll。

在顶部定义 xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"

2.3 引用方法