如何传递一个整数作为转换器参数？

我尝试绑定到一个整数属性:

<RadioButton Content="None"
IsChecked="{Binding MyProperty,
Converter={StaticResource IntToBoolConverter},
ConverterParameter=0}" />

我的转换器是:

[ValueConversion(typeof(int), typeof(bool))]
public class IntToBoolConverter : IValueConverter
{
public object Convert(object value, Type t, object parameter, CultureInfo culture)
{
return value.Equals(parameter);
}


public object ConvertBack(object value, Type t, object parameter, CultureInfo culture)
{
return value.Equals(false) ? DependencyProperty.UnsetValue : parameter;
}
}

问题是，当我的转换器被调用时，参数是字符串。我需要它是一个整数。我当然可以解析字符串，但是我必须这么做吗？

谢谢你的帮助 康斯坦丁

95437 次浏览
小开

Don't use value.Equals. Use:

  Convert.ToInt32(value) == Convert.ToInt32(parameter)
小开

It would be nice to somehow express the type information for the ConverterValue in XAML, but I don't think it is possible as of now. So I guess you have to parse the Converter Object to your expected type by some custom logic. I don't see another way.

小开
最佳答案

Here ya go!

<RadioButton Content="None"
xmlns:sys="clr-namespace:System;assembly=mscorlib">
<RadioButton.IsChecked>
<Binding Path="MyProperty"
Converter="{StaticResource IntToBoolConverter}">
<Binding.ConverterParameter>
<sys:Int32>0</sys:Int32>
</Binding.ConverterParameter>
</Binding>
</RadioButton.IsChecked>
</RadioButton>

The trick is to include the namespace for the basic system types and then to write at least the ConverterParameter binding in element form.

小开

For completeness, one more possible solution (perhaps with less typing):

<Window
xmlns:sys="clr-namespace:System;assembly=mscorlib" ...>
<Window.Resources>
<sys:Int32 x:Key="IntZero">0</sys:Int32>
</Window.Resources>


<RadioButton Content="None"
IsChecked="{Binding MyProperty,
Converter={StaticResource IntToBoolConverter},
ConverterParameter={StaticResource IntZero}}" />

(Of course, Window can be replaced with UserControl, and IntZero may be defined closer to the place of actual usage.)

小开

Not sure why WPF folks tend to be disinclined towards using MarkupExtension. It is the perfect solution for many problems including the issue mentioned here.

public sealed class Int32Extension : MarkupExtension
{
public Int32Extension(int value) { this.Value = value; }
public int Value { get; set; }
public override Object ProvideValue(IServiceProvider sp) { return Value; }
};

If this markup extension is defined in XAML namespace 'local:', then the original poster's example becomes:

<RadioButton Content="None"
IsChecked="{Binding MyProperty,
Converter={StaticResource IntToBoolConverter},
ConverterParameter={local:Int32 0}}" />

This works because the markup extension parser can see the strong type of the constructor argument and convert accordingly, whereas Binding's ConverterParameter argument is (less-informatively) Object-typed.


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