WPF自定义控件Textbox 带水印 以及错误信息显示

<UserControl x:Class="TextBoxEdit.SelfWateMarkTextbox"
             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"  >
    <Grid>
        <StackPanel Orientation="Horizontal" Height="35">
            <Label Name="IsInput" Foreground="Red" VerticalContentAlignment="Center" HorizontalContentAlignment="Center" Width="20">*</Label>
            <TextBox VerticalContentAlignment="Center"  Width="300" Height="25" x:Name="textBox1"  />
            <Border  Name="IsErrorShowBorder" BorderThickness="1"  Height="27" CornerRadius="15"  Visibility="Hidden">
                <Label Name="IsError"  Foreground="Red" Background="LightPink" VerticalContentAlignment="Center" HorizontalContentAlignment="Center">错误信息</Label>
            </Border>
            <TextBox VerticalContentAlignment="Center" Text="{Binding IsErroShow}"  Height="25" x:Name="txtErrorShow"   Visibility="Hidden"/>
        </StackPanel>
    </Grid>
</UserControl>

private const string defaultText = "";

        private const string IsInputText = "";

        private const string IsErrorText = "";


        public SelfWateMarkTextbox()
        {
            InitializeComponent();
            this.Loaded += new RoutedEventHandler(WateMarkTextbox_Loaded);

            this.GotFocus += new RoutedEventHandler(WateMarkTextbox_GotFocus);

            this.LostFocus += new RoutedEventHandler(WateMarkTextbox_LostFocus);

            this.textBox1.TextChanged += new TextChangedEventHandler(TextBox1_TextChanged);

            this.txtErrorShow.TextChanged += new TextChangedEventHandler(txtErrorShow_TextChanged);

        }

        void txtErrorShow_TextChanged(object sender, TextChangedEventArgs e)
        {
            if (!string.IsNullOrWhiteSpace(this.txtErrorShow.Text) && txtErrorShow.Text.ToLower() == "true")
            {
                IsErrorShowBorder.Visibility = Visibility.Visible;
            }
            else
            {
                IsErrorShowBorder.Visibility = Visibility.Hidden;
            }
        }
        void TextBox1_TextChanged(object sender, TextChangedEventArgs e)
        {
            if (!string.IsNullOrWhiteSpace(this.textBox1.Text) || this.textBox1.IsFocused)
            {
                this.textBox1.Text = this.textBox1.Text;
            }
            else
            {
                this.textBox1.Text = Watermark;
            }
        }

        void WateMarkTextbox_LostFocus(object sender, RoutedEventArgs e)
        {
            if (string.IsNullOrEmpty(this.textBox1.Text))
            {
                this.textBox1.Text = string.Empty;
            }
        }

        void WateMarkTextbox_GotFocus(object sender, RoutedEventArgs e)
        {
            if (this.textBox1.Text.Equals(Watermark))
            {
                this.textBox1.Text = string.Empty;
            }
        }

        void WateMarkTextbox_Loaded(object sender, RoutedEventArgs e)
        {
            this.textBox1.Text = Watermark;
            this.IsInput.Content = IsRequired;
            this.IsError.Content = IsErrorMessage;
        }

        public string Watermark
        {
            get
            {
                string result = (string)GetValue(WatermarkProperty);

                if (string.IsNullOrEmpty(result))
                {
                    result = defaultText;
                }

                return result;
            }

            set { SetValue(WatermarkProperty, value); }
        }

        public string IsRequired
        {
            get
            {
                string result = (string)GetValue(IsRequiredProperty);

                if (string.IsNullOrEmpty(result))
                {
                    result = IsInputText;
                }

                return result;
            }

            set { SetValue(IsRequiredProperty, value); }
        }

        public string IsErrorMessage
        {
            get
            {
                string result = (string)GetValue(IsErrorMessageProperty);

                if (string.IsNullOrEmpty(result))
                {
                    result = IsErrorText;
                }

                return result;
            }

            set { SetValue(IsErrorMessageProperty, value); }
        }

        public string IsErrorShow
        {
            set
            {
                txtErrorShow.Text = null;
                txtErrorShow.Text = value;
            }

        }

        readonly DependencyProperty WatermarkProperty =
                   DependencyProperty.Register("Watermark", typeof(string), typeof(SelfWateMarkTextbox), new UIPropertyMetadata(defaultText));


        public static readonly DependencyProperty IsRequiredProperty =
             DependencyProperty.Register("IsRequired", typeof(string), typeof(SelfWateMarkTextbox), new UIPropertyMetadata(IsInputText));

        public static readonly DependencyProperty IsErrorMessageProperty =
            DependencyProperty.Register("IsErrorMessage", typeof(string), typeof(SelfWateMarkTextbox), new UIPropertyMetadata(IsErrorText));

 <my:SelfWateMarkTextbox  x:Name="wateMarkTextbox1" VerticalAlignment="Top"  IsRequired="*"  Watermark="请输入姓名" IsErrorMessage="请输入正常的姓名"  Height="35" />
        <Button Content="确定" Height="23" Width="120" Click="Button_Click"></Button>