绑定ComboBox控件到一个单独的源在DataGrid中 [英] Binding a Combobox control to a separate source within a DataGrid

问题描述

林试图DataGrid中，这将允许用户选择一个不同的表来的值内使用ComboBox。即时通讯使用一个ViewModel类DataContext的，这包含了对终端的TerminalTypes和的ObservableCollection另一个。

Im attempting to use a ComboBox within a DataGrid which will allow the user to select a value coming from a different table. Im using a ViewModel class as the DataContext and this contains an ObservableCollection for Terminals and another for TerminalTypes.

对电网的结合是好的，所有的行填充和DataGridTextColumns都显示正确的数据，但我的组合框是空的。

The binding on the grid is fine, all the rows are populated and the DataGridTextColumns all show the correct data, my ComboBox however is empty.

我知道的ObservableCollection林试图绑定到已被填充，如果我移动组合框的DataGrid外面按预期工作。

I know that the ObservableCollection Im attempting to bind to has been populated and if I move the ComboBox outside of the DataGrid it works as expected.

<my:DataGrid Name="MenuDetailGrid" AutoGenerateColumns="False" ItemsSource="{Binding Terminals}">
    <my:DataGrid.Columns>
        <my:DataGridTextColumn Header="Terminal Type ID" Binding="{Binding TERMINAL_TYPE_ID}" IsReadOnly="True" />
        <my:DataGridTemplateColumn Header="Terminal Type">
            <my:DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <ComboBox DisplayMemberPath="TTYPE_NAME" SelectedValuePath="TERMINAL_TYPE"
                              SelectedValue="{Binding TERMINAL_TYPE_ID}" 
                              ItemsSource="{Binding TerminalTypes}" />

                </DataTemplate>
            </my:DataGridTemplateColumn.CellTemplate>
        </my:DataGridTemplateColumn>

显然约束力的行为是在不同的组合框时DataGrid的一部分，但是我有点难倒，为什么？

Obviously the binding behaviour is different on the ComboBox when part of the DataGrid but Im a bit stumped as to why?

有人可以帮我明白我做错了吗？

Can someone please help me understand what I am doing wrong?

推荐答案

的结合行为是一样的。然而就是在DataContext由ItemsControl中设置为当前项目一个DataTemplate，这是你的情况端子 -collection的成员。因此，TerminalTypes收集无法找到（除非你实现它也是在您的项目）。

The binding behaviour is the same. However is the DataContext in a DataTemplate set by the ItemsControl to current item and this is in your case a member of the Terminals-collection. Therefore, the TerminalTypes-collection could not be found (unless you implement it also on your item).

你可以做的是在你的绑定使用相对源。有了这个，你可以导航到DataGrid的DataContext的，然后访问 TerminalTypes -Collection：

What you can do is to use a relative source in your Binding. With this, you can navigate to the DataGrid's DataContext and then access your TerminalTypes-Collection:

<ComboBox DisplayMemberPath="TTYPE_NAME"
    SelectedValuePath="TERMINAL_TYPE"
    SelectedValue="{Binding TERMINAL_TYPE_ID}"
    ItemsSource="{Binding DataContext.TerminalTypes,RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=DataGrid}" /> 

希望这有助于。做一个评论，如果没有。

Hope this helped. Make a comment if not.

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