WPF：对数据网格内容变化做出反应的最佳方法？

Question

I have a datagrid with two readonly DataGridTextColumns and one DataGridTemplateColumn with a TextBox in it. (The reason I went for a textbox rather than just a text column is because i wanted a context menu on each datagrid row with an option to rename which which turned out to be easiest with this approach).

        <DataGrid Grid.Row="0" Name="dgUsers" AutoGenerateColumns="False" ItemsSource="{Binding Path=Users, Mode=TwoWay}">
            <DataGrid.RowStyle>
                <Style TargetType="{x:Type DataGridRow}">
                    <Setter Property="ContextMenu" Value="{StaticResource dataGridRowContextMenu}" />
                </Style>
            </DataGrid.RowStyle>
            <DataGrid.Columns>

                <DataGridTextColumn Header="Name" Binding="{Binding Name}" IsReadOnly="True" />

                <DataGridTemplateColumn Width="Auto" Header="Middle Name">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <TextBox Name="middleName" Text="{Binding MiddleName}" Style="{StaticResource DataGridTextBox}"/>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>

                <DataGridTextColumn Header="Last Name" Binding="{Binding LastName}" IsReadOnly="True"/>


            </DataGrid.Columns>
        </DataGrid>

The contents of the datagrid are twoway binded to a collection of objects in my view model. Each row corresponds to a User. Those Users objects in my viewmodel are hooked up to a database. I want to make things such that when a user changes the text in the editable column (the column where each row has a text box), the database is modified accordingly (after some data validation and such).

My question is: what is a good MVVM way of listening for a change in the template column and reacting to it?

I tried using the TextChanged event:

                    <DataGridTemplateColumn Width="Auto" Header="Middle Name">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <TextBox Name="middleName" Text="{Binding MiddleName}" Style="{StaticResource DataGridTextBox}"
                                     TextChanged="middleName_TextChanged"/>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>

But then the middleName_TextChanged() method in my xaml.cs code behind gets called with every character added to the text box... ideally I want a method that only gets called when the focus leaves the text box (not with every character added).

I also considered launching the method to do input validation from the set method of the Property of User that this column is binded to (the set method of User.MiddleName) but this too is called with each character inserted into the text box.

Answer 1

In your .xaml file add a CollectionViewSource like this

 <Window.Resources>
        <CollectionViewSource x:Key="ItemCollectionViewSource"  CollectionViewType="ListCollectionView"/>
 </Window.Resources>

And then in your DataGrid put the DataContext to ItemCollectionViewSource like this

DataContext="{StaticResource ItemCollectionViewSource}"

Now in code behind set your database to the ItemCollectionViewSource like this

CollectionViewSource itemCollectionViewSource;
itemCollectionViewSource = (CollectionViewSource)(FindResource("ItemCollectionViewSource"));
itemCollectionViewSource.Source = YourDataBase;

Now any changes in a twoway binding would reflect on the database.