DataTemplate中的EventToCommand [英] EventToCommand in DataTemplate

问题描述

我正在使用MVVM-light-Toolkit中的EventToCommand类来处理WPF-DataGrid中的AutoGeneratingColumn-Event.它在我的Main-DataGrid中可以正常工作，但是我在RowDetailsTemplate中使用了另一个DataGrid，在这里我遇到了一个问题: AutoGeneratingColumn在EventToCommand-Object生成之前触发.有解决这个问题的方法吗? 这是我的Xaml代码的一部分:

I'm using the EventToCommand Class from the MVVM-light-Toolkit to handle the AutoGeneratingColumn-Event in the WPF-DataGrid. It works fine in my Main-DataGrid, but I use another DataGrid in the RowDetailsTemplate and here I got a problem: The AutoGeneratingColumn fires before the EventToCommand-Object was generated. Is there a solution for this problem? Here is a piece of my Xaml-Code:

<DataGrid DockPanel.Dock="Top" AutoGenerateColumns="True" Name="table" VerticalAlignment="Top" ItemsSource="{Binding PartBatchList}" IsReadOnly="True">
    <i:Interaction.Triggers>
            <i:EventTrigger EventName="AutoGeneratingColumn">
                <hgc:EventToCommand Command="{Binding AutoGeneratingColumnCommand}" PassEventArgsToCommand="True"/>
            </i:EventTrigger>
        </i:Interaction.Triggers>
    <DataGrid.RowDetailsTemplate>
        <DataTemplate>
            <StackPanel Margin="30,0,30,30" Orientation="Vertical">
                <Border CornerRadius="4" Padding="5" Background="White">
                    <DataGrid ItemsSource="{Binding Workpieces}"  
                                    CanUserReorderColumns="False" CanUserResizeColumns="False" CanUserSortColumns="False"
                                    AutoGenerateColumns="True" AutoGeneratingColumn="WorkpieceListAutoGeneratingColumn">
                        <i:Interaction.Triggers>
                            <i:EventTrigger EventName="AutoGeneratingColumn">
                                <hgc:EventToCommand Command="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type DataGrid},AncestorLevel=2}, Path=DataContext.AutoGeneratingColumnCommand}" PassEventArgsToCommand="True"/>
                            </i:EventTrigger>
                        </i:Interaction.Triggers>
                    </DataGrid>
                </Border>
            </StackPanel>
        </DataTemplate>
    </DataGrid.RowDetailsTemplate>

</DataGrid>

代码隐藏文件中的事件处理程序WorkpieceListAutoGeneratingColumn被调用，而我的ViewModel中的命令从不被调用.

The Event-Handler WorkpieceListAutoGeneratingColumn in the Code-Behind File is called, the Command in my ViewModel is never called.

安德烈亚斯(Andreas)

Andreas

推荐答案

原因应该是您不能在相同的对象/事件组合上具有事件andler和命令事件.从您的DataGrid中删除AutoGeneratingColumn="WorkpieceListAutoGeneratingColumn"，应调用该命令.

我自己曾经遇到问题:-)

Had the problem once myself :-)

修改

如果后面的代码中需要事件处理程序，请删除EventToCommand并在后面的代码中调用命令，例如

If you need the eventhandler in the code behind, remove the EventToCommand and call the command in your code behind, e.g.

public void WorkpieceListAutoGeneratingColumn(object sender, DataGridAutoGeneratingColumnEventArgs args) {
    var vm = ((YourViewModel) this.DataContext);
    if (vm.AutoGeneratingColumnCommand.CanExecute(eventArgs)) 
        vm.AutoGeneratingColumnCommand.Execute(eventArgs);
}

但是，我认为第一个选择是更好的选择.

编辑2

好，环顾四周，看来<i:Interaction.Triggers/>仅在对象已渲染并且发生用户交互之后才能起作用(因此命名?).好吧，这意味着仅存在一些事件-在对象构造期间调用的事件-EventToCommand机制无法处理.在这种情况下，可以使用后面的代码从那里调用您的命令，请参阅我的第一次编辑.

OK, had some look around and it seems that <i:Interaction.Triggers/> only works after the object is already rendered and user interaction takes place (hence the name?). Well, this means that there are simply just some events - the ones that are called during the construction of the object - that cannot be handled by the EventToCommand mechanism. In these cases it is OK to use code behind to call your command from there, see my first edit.

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