Question

我的自定义控件看起来像这样：

generic.xaml

<Style TargetType="controls:MyControl">
  <Setter Property="Template">
    <Setter.Value>
      <ControlTemplate TargetType="controls:MyControl">
        <Grid>
          <Grid.RowDefinitions>
            <RowDefinition Height="20" />
            <RowDefinition Height="20" />
          </Grid.RowDefinitions>
          <TextBox Grid.Row="0"
                   Text="{Binding ElementName=slider, Path=Value}" />
          <Slider Grid.Row="1" Name="slider" Width="120"
                  Minimum="1" Maximum="12"
                  Value="{Binding Mode=TwoWay,
                          RelativeSource={RelativeSource TemplatedParent},
                          Path=Value}"/>
        </Grid>
      </ControlTemplate>
    </Setter.Value>
  </Setter>
</Style>

MyControl.cs

public static readonly DependencyProperty ValueProperty =
  DependencyProperty.Register("Value",
  typeof(double),
  typeof(MyControl),
  new PropertyMetadata(0d, OnValueChanged));

  public double Value
  {
    get { return (double)base.GetValue(ValueProperty); }
    set { base.SetValue(ValueProperty, value); }
  }

  private static void OnValueChanged(DependencyObject source,
                                     DependencyPropertyChangedEventArgs e)
  {
    MyControl myControl = (MyControl)source;
    myControl.OnValueChanged((double)e.OldValue, (double)e.NewValue);
  }

  protected virtual void OnValueChanged(double oldValue, double newValue)
  {
    double coercedValue = CoerceValue(newValue);
    if (coercedValue != newValue)
    {
      this.Value = coercedValue;
    }
  }

  private double CoerceValue(double value)
  {
    double limit = 7;
    if (value > limit)
    {
      return limit;
    }
    return value;
  }

TextBox只是一个显示值的假人。

现在，当我将此控件添加到Application时，我可以将Slider值设置为大于7，尽管我的DependencyProperty的值设置为7.

我做错了什么？ TwoWayBinding在这种情况下不起作用吗？

提前致谢

Answer 1

我的重复步骤： -

在VS2010中创建一个全新的Silverlight应用程序，调用SilverlightApplication1。
将新的“Silverlight Templated Control”添加到silverlight项目中，并将其命名为“MyControl”。

将内部内容或ControlTemplate复制到themes / Generic.xaml文件的ControlTemplate中。整个通用文件如下所示： -

<Style TargetType="local:MyControl">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="local:MyControl">
                <Grid>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="20" />
                        <RowDefinition Height="20" />
                    </Grid.RowDefinitions>
                    <TextBox Grid.Row="0"
                   Text="{Binding ElementName=slider, Path=Value}" />
                    <Slider Grid.Row="1" Name="slider" Width="120"
                  Minimum="1" Maximum="12"
                  Value="{Binding Mode=TwoWay,
                          RelativeSource={RelativeSource TemplatedParent},
                          Path=Value}"/>
                </Grid>

            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

将您放置在MyControl.cs中的C＃复制。整个文件看起来像： -

使用System.Windows; 使用System.Windows.Controls;

namespace SilverlightApplication1
{
    public class MyControl : Control
    {
        public MyControl()
        {
            this.DefaultStyleKey = typeof(MyControl);
        }

        public static readonly DependencyProperty ValueProperty =
  DependencyProperty.Register("Value",
  typeof(double),
  typeof(MyControl),
  new PropertyMetadata(0d, OnValueChanged));

        public double Value
        {
            get { return (double)base.GetValue(ValueProperty); }
            set { base.SetValue(ValueProperty, value); }
        }

        private static void OnValueChanged(DependencyObject source,
                                           DependencyPropertyChangedEventArgs e)
        {
            MyControl myControl = (MyControl)source;
            myControl.OnValueChanged((double)e.OldValue, (double)e.NewValue);
        }

        protected virtual void OnValueChanged(double oldValue, double newValue)
        {
            double coercedValue = CoerceValue(newValue);
            if (coercedValue != newValue)
            {
                this.Value = coercedValue;
            }
        }

        private double CoerceValue(double value)
        {
            double limit = 7;
            if (value > limit)
            {
                return limit;
            }
            return value;
        }

    }
}

将一个MyControl实例添加到MainPage.xaml，现在看起来像： -

<UserControl x:Class="SilverlightApplication1.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:SilverlightApplication1"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400">

    <Grid x:Name="LayoutRoot" Background="White">
        <local:MyControl />
     </Grid>

 </UserControl>

运行解决方案，工作正常。

Silverlight中的强制不起作用

1 个答案: