如何使用自定义类中定义的依赖属性？答案

【问题标题】：How to use a dependency property defined in custom class?如何使用自定义类中定义的依赖属性？
【发布时间】：2014-02-18 08:06:19
【问题描述】：

我有一个为TextBox 类定义一些自定义依赖属性的类：

public class DependencyProperties:FrameworkElement 
{
    public static readonly DependencyProperty SelectionBeginProperty = DependencyProperty.Register("SelectionBegin", typeof(int), typeof(TextBox),
                                                          new UIPropertyMetadata(0, SelectionStartDependencyPropertyChanged));
    public static readonly DependencyProperty SelectionLengthProperty = DependencyProperty.Register("SelectionLength", typeof(int), typeof(TextBox),
                                                            new UIPropertyMetadata(0, SelectionLengthDependencyPropertyChanged));
    public static readonly DependencyProperty ChildrenProperty = DependencyProperty.Register("Children", typeof (string), typeof (TreeView));

    static DependencyProperties() 
    {

    }
 ...     
}

当我尝试在 Xaml 中使用这些属性时：

<TextBox Name="TextBox_1735"
         SelectionBegin="{Binding TextBox_1735SelectionBegin, UpdateSourceTrigger=PropertyChanged}" 
         SelectionLength="{Binding TextBox_1735SelectionLength, UpdateSourceTrigger=PropertyChanged}" />

它会引发属性SelectionBegin 无法解析的异常。

【问题讨论】：

在您的情况下，您需要实现 attached 依赖属性 - MSDN link。并像这样使用：<TextBox local:DependencyProperties.SelectionBegin={...} />.
我试过了。但现在我得到另一个错误：“不能在'TextBox'类型的'SetSelectionBegin'属性上设置'Binding'。只能在DependencyObject的DependencyProperty上设置'Binding'。”
@Sergiu 你在实现custom attached property..时在某个地方犯了一个错误。

标签： c# wpf textbox dependency-properties

【解决方案1】：

您应该寻找的是Attached Properties，因为标准依赖属性必须在控件本身中声明。您也可以从 TextBox 继承并在派生类中添加您的依赖属性。

【讨论】：

【解决方案2】：

我创建了一个简单的类，看起来应该带有一些注释。通过这个例子，你可以让自己成为剩余的属性。

AttachedProperty

public class DependencyProperties
{
    #region Here put your property declaration

    public static readonly DependencyProperty SelectionBeginProperty;

    public static void SetSelectionBegin(DependencyObject DepObject, int value)
    {
        DepObject.SetValue(SelectionBeginProperty, value);
    }

    public static int GetSelectionBegin(DependencyObject DepObject)
    {
        return (int)DepObject.GetValue(SelectionBeginProperty);
    }

    #endregion

    #region Here in constructor register you property

    static DependencyProperties()
    {
        SelectionBeginProperty = DependencyProperty.RegisterAttached("SelectionBegin", // RegisterAttached
                                                             typeof(int),              // Type of your property
                                                             typeof(DependencyProperties), // Name of your class
                                                             new UIPropertyMetadata(0, SelectionStartDependencyPropertyChanged));
    }

    #endregion

    private static void SelectionStartDependencyPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e) 
    {
        // Some logic
        var textBox = sender as TextBox;

        if (textBox == null) 
        {
            return;
        }

        if (e.NewValue is int && ((int)e.NewValue) > 0)
        {
            textBox.Background = Brushes.Red;
        }
    }
}

XAML

<Window x:Class="AttachedPropertyHelp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:AttachedPropertyHelp"
        Name="MyWindow" Title="MainWindow"
        Height="350" Width="525">

    <Grid>
        <TextBox Name="MyTextBox" 
                 local:DependencyProperties.SelectionBegin="{Binding Path=Width, ElementName=MyWindow}" 
                 Width="100"
                 Height="30" />
    </Grid>
</Window>

对于attached依赖属性设置了WindowInt类型的Width，如果大于零，则TextBox标记为红色背景。

【讨论】：