Bind to a method in WPF?

How do you bind to an objects method in this scenario in WPF?

public class RootObject
{
    public string Name { get; }

    public ObservableCollection<ChildObject> GetChildren() {...}
}

public class ChildObject
{
    public string Name { get; }
}

XAML:

<TreeView ItemsSource="some list of RootObjects">
    <TreeView.Resources>
        <HierarchicalDataTemplate DataType="{x:Type data:RootObject}" 
                                  ItemsSource="???">
            <TextBlock Text="{Binding Path=Name}" />
        </HierarchicalDataTemplate>
        <HierarchicalDataTemplate DataType="{x:Type data:ChildObject}">
            <TextBlock Text="{Binding Path=Name}" />
        </HierarchicalDataTemplate>
    </TreeView.Resources>
</TreeView>

Here I want to bind to the GetChildren method on each RootObject of the tree.

EDIT Binding to an ObjectDataProvider doesn't seem to work because I'm binding to a list of items, and the ObjectDataProvider needs either a static method, or it creates it's own instance and uses that.

For example, using Matt's answer I get:

System.Windows.Data Error: 33 : ObjectDataProvider cannot create object; Type='RootObject'; Error='Wrong parameters for constructor.'

System.Windows.Data Error: 34 : ObjectDataProvider: Failure trying to invoke method on type; Method='GetChildren'; Type='RootObject'; Error='The specified member cannot be invoked on target.' TargetException:'System.Reflection.TargetException: Non-static method requires a target.

---

Another approach that might work for you is to create a custom IValueConverter that takes a method name as a parameter, so that it would be used like this:

ItemsSource="{Binding 
    Converter={StaticResource MethodToValueConverter},
    ConverterParameter='GetChildren'}"

This converter would find and invoke the method using reflection. This requires the method to not have any arguments.

Here's an example of such a converter's source:

public sealed class MethodToValueConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var methodName = parameter as string;
        if (value==null || methodName==null)
            return value;
        var methodInfo = value.GetType().GetMethod(methodName, new Type[0]);
        if (methodInfo==null)
            return value;
        return methodInfo.Invoke(value, new object[0]);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException("MethodToValueConverter can only be used for one way conversion.");
    }
}

And a corresponding unit test:

[Test]
public void Convert()
{
    var converter = new MethodToValueConverter();
    Assert.AreEqual("1234", converter.Convert(1234, typeof(string), "ToString", null));
    Assert.AreEqual("ABCD", converter.Convert(" ABCD ", typeof(string), "Trim", null));

    Assert.IsNull(converter.Convert(null, typeof(string), "ToString", null));

    Assert.AreEqual("Pineapple", converter.Convert("Pineapple", typeof(string), "InvalidMethodName", null));
}

Note that this converter does not enforce the targetType parameter.

---

Not sure how well it will work in your scenario, but you can use the MethodName property on ObjectDataProvider to have it call a specific method (with specific parameters if you MethodParameters property) to retrieve its data.

Here's a snippet taken directly from the MSDN page:

<Window.Resources>
    <ObjectDataProvider ObjectType="{x:Type local:TemperatureScale}"
        MethodName="ConvertTemp" x:Key="convertTemp">
        <ObjectDataProvider.MethodParameters>
            <system:Double>0</system:Double>
             <local:TempType>Celsius</local:TempType>
        </ObjectDataProvider.MethodParameters>
    </ObjectDataProvider>
</Window.Resources>

So that's an ObjectDataProvider that's calling a "ConvertTemp" method on an instance of a "TemperatureScale" class, passing two parameters (0 and TempType.Celsius ).

---

Do you have to bind to the method?

Can you bind to a property who's getter is the method?

public ObservableCollection<ChildObject> Children
{
   get
   {
      return GetChildren();
   }
}

链接地址: http://www.djcxy.com/p/44630.html

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