在IValueConverter类中定义属性 [英] Defining a Property in a IValueConverter class

问题描述

我需要在转换器类中定义DependencyProperty，因为我需要此数据进行转换，并且此数据在另一个对象中，而不是我要绑定的对象。

I need to define a DependencyProperty in a converter class because I need this data to make the conversion and this data is in another object, not the one I'm binding to.

我的转换器类如下：

public class LEGOMaterialConverter   : DependencyObject, IValueConverter
{
    public DependencyProperty MaterialsListProperty = DependencyProperty.Register("MaterialsList", typeof(Dictionary<int, LEGOMaterial>), typeof(LEGOMaterialConverter));

    public Dictionary<int, LEGOMaterial> MaterialsList
    {
        get
        {
            return (Dictionary<int, LEGOMaterial>)GetValue(MaterialsListProperty);
        }
        set
        {
            SetValue(MaterialsListProperty, value);
        }
    }

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        LEGOMaterial material = null;

        MaterialsList.TryGetValue((int)value, out material);

        return material;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

然后在Window上实例化它。区域：

Then I'm instanciating it on the Window.REsources area:

<Window.Resources>
    <local:LEGOMaterialConverter x:Key="MaterialsConverter" MaterialsList="{Binding Path=Materials}" />
</Window.Resources>

我遇到以下错误：

   'MaterialsList' property was already registered by 'LEGOMaterialConverter'.

有人对此错误有线索吗？

Does anyone have a clue on this error?

推荐答案

尝试这样做（仅举一个例子）：

Try doing it like this (just an example):

public class ValueConverterWithProperties : MarkupExtension, IValueConverter
{
    public int TrueValue { get; set; }

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        return this;
    }

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if ((int) value == TrueValue)
        {
            return true;
        }
        return false;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

通知我来自标记扩展，允许我使用像这样：

notice I derive from markup extension to allow me to use it like this:

<Window x:Class="Converter.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:converter="clr-namespace:Converter"
    Title="MainWindow" Height="350" Width="525">
<Grid>
    <CheckBox IsChecked="{Binding item, Converter={converter:ValueConverterWithProperties TrueValue=5}}"></CheckBox>
    <CheckBox IsChecked="{Binding item2, Converter={converter:ValueConverterWithProperties TrueValue=10}}"></CheckBox>
</Grid>

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