IMultiValueConverter 的 DataGridTextColumn 绑定不起作用

Question

我有这个 DataGridTextColumn，我正试图在其上放置一个 IMultiValueConverter。

在转换器中，当我执行以下操作时，GenericDataGrid 的绑定： Console.WriteLine(values[1].GetType()); 返回 MS.Internal.NamedObject

我该如何解决这个问题，以便它为我提供对 DataGrid 的引用？

<DataGrid Name="GenericDataGrid"
          AutoGenerateColumns="False" 
          ItemsSource="{Binding UserCollection}">
    <DataGrid.Columns>
        <DataGridTextColumn Binding="{Binding Path=Job_Title}">
            <DataGridTextColumn.Header>
                <MultiBinding Converter="{StaticResource metaDataDisplayNameConverter}">
                    <MultiBinding.Bindings>
                        <Binding RelativeSource="{x:Static RelativeSource.Self}"/>
                        <Binding ElementName="GenericDataGrid" />
                    </MultiBinding.Bindings>
                </MultiBinding>
            </DataGridTextColumn.Header>
        </DataGridTextColumn>
    </DataGrid.Columns>
</DataGrid>

[编辑]

这是我制作绑定代理后的结果，但是 Path="Data" 有问题。输入后我得到 Object reference not set to an instance of an object.

你能看出代理绑定有什么问题吗？

<DataGrid Name="GenericDataGrid"
          AutoGenerateColumns="False" 
          ItemsSource="{Binding UserCollection}">
    <DataGrid.Resources>
        <proxy:FreezableBindingProxy x:Key="proxy" Data="{Binding ElementName=GenericDataGrid}" />
    </DataGrid.Resources>
    <DataGrid.Columns>
        <DataGridTextColumn Binding="{Binding Path=Job_Title}">
            <DataGridTextColumn.Header>
                <MultiBinding Converter="{StaticResource metaDataDisplayNameConverter}">
                    <MultiBinding.Bindings>
                        <Binding RelativeSource="{x:Static RelativeSource.Self}"/>
                        <Binding Source="{StaticResource proxy}" Path="Data" />
                    </MultiBinding.Bindings>
                </MultiBinding>
            </DataGridTextColumn.Header>
        </DataGridTextColumn>
    </DataGrid.Columns>
</DataGrid>

[编辑 2]

另一个相关的问题。在转换器中，当我尝试获取 DataGrid 的 ItemsSource 时，它抛出了一堆错误。知道为什么会这样吗？

我唯一追求的是集合类型，也许有更好的方法。
实际上我收回这一点，重要的是集合中的单一项目类型。

public object Convert(object[] values, System.Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
    string DisplayName = "Col";

    object ColumnObject = values[0];
    DataGrid dg = (DataGrid)values[1];
    string columnPropertyName = parameter.ToString();

    var collection = dg.ItemsSource; //*****Fails here*****
    Type collectionType = collection.GetType();
    Type itemType = collectionType.GetGenericArguments().Single();
    PropertyInfo prop = itemType.GetProperties().SingleOrDefault(p => p.Name.Equals(columnPropertyName));

    //....Gets properties display name attribute here.

    return DisplayName;
}

错误：

A first chance exception of type 'System.NullReferenceException' occurred in UserManagement.dll A first chance exception of type 'System.NullReferenceException' occurred in System.Xaml.dll A first chance exception of type 'System.NullReferenceException' occurred in PresentationFramework.dll A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in mscorlib.dll

Answer 1

Rachel 在这个问题上给出了 good explanation。

The DataGridColumn is not actually part of the VisualTree, so bindings on the class cannot find their source

她为此提供了一个解决方法，我尝试了以下步骤并且成功了。

1.Create新建一个classBindingProxy并添加到项目中，代码来自this answer, I add a try-catch抑制Object reference not set to an instance of an object抛出的异常设计时的构造函数。

public class BindingProxy : Freezable
{
    #region Overrides of Freezable

    protected override Freezable CreateInstanceCore()
    {
        try
        {
            return new BindingProxy();
        }
        catch
        {
            return null;
        }
    }

    #endregion

    public object Data
    {
        get { return (object)GetValue(DataProperty); }
        set { SetValue(DataProperty, value); }
    }

    public static readonly DependencyProperty DataProperty =
        DependencyProperty.Register("Data", typeof(object),
                                     typeof(BindingProxy));
}

2.And XAML 代码

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApplication1"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <local:BindingProxy x:Key="proxy" Data="{Binding ElementName=GenericDataGrid}" />
        <local:MetaDataDisplayNameConverter x:Key="metaDataDisplayNameConverter" />
    </Window.Resources>
    <Grid>
        <DataGrid Name="GenericDataGrid"
          AutoGenerateColumns="False" 
          ItemsSource="{Binding UserCollection}">
            <DataGrid.Columns>
                <DataGridTextColumn Binding="{Binding Path=Job_Title}">
                    <DataGridTextColumn.Header>
                        <MultiBinding Converter="{StaticResource metaDataDisplayNameConverter}">
                            <MultiBinding.Bindings>
                                <Binding RelativeSource="{x:Static RelativeSource.Self}" />
                                <Binding Source="{StaticResource proxy}" Path="Data" />
                            </MultiBinding.Bindings>
                        </MultiBinding>
                    </DataGridTextColumn.Header>
                </DataGridTextColumn>
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>

IMultiValueConverter 的 DataGridTextColumn 绑定不起作用

DataGridTextColumn binding for IMultiValueConverter not working

c#

wpf

imultivalueconverter

IMul​​tiValueConverter 的 DataGridTextColumn 绑定不起作用

DataGridTextColumn binding for IMultiValueConverter not working

c#

wpf

imultivalueconverter

IMultiValueConverter 的 DataGridTextColumn 绑定不起作用