当选择更改时，如何停止Combobox更新源数据？

Question

I have a ComboBox displaying people, a TextBox for firstname, a TextBox for lastname, a Button to save the entered data. The user may enter what ever he wants in the TextBox es and when he clicks the 'save' button the contents of the TextBox es should be saved to the currently selected person.

This is how my TextBox es look like in XAML:

<Grid>
    <Combobox x:Name="cbPerson" ItemsSource={Binding Source={StaticResource collection_people}
          SelectedValue={Binding Path=Firstname} DisplayMemberPath={Binding Path=Firstname}
          SelectedValuePath={Binding Path=Firstname}/>

    <Textbox x:Name="tbFirstname" Text="{Binding Path=name, Mode=TwoWay,
          UpdateSourceTrigger=Explicit}}" Width="Auto"/>

    <Textbox x:Name="tbLastname" Text="{Binding Path=name, Mode=TwoWay, 
          UpdateSourceTrigger=Explicit}}" Width="Auto">
</Grid>

This is how my Button function looks like:

private void btnSave_Click(object sender, RoutedEventArgs e)
{
    tbFirstname.GetBindingExpression(TextBox.TextProperty).UpdateSource();
    tbLastname.GetBindingExpression(TextBox.TextProperty).UpdateSource();
}

In my Person class I implemented INotifyPropertyChanged interface in order for the TwoWay binding to work.

When I select an item from the ComboBox the TextBox es get filled with the according data. I can then edit the TextBox es and save the data to the object by pressing the save button. Everything works as you would expect except for one thing:

For instance, when I select "Paul" from the ComboBox and change the text of the firstname TextBox from "Paul" to "Leo" and then select another item from the ComboBox WITHOUT clicking the save button, the object previous object ("Paul") gets updated nevertheless.

Why is that and how can I fix this? I haven't had any success finding something related to this problem.

Answer 1

Can you try this for your XAML code?

<Grid>
    <ComboBox x:Name="cbPerson" ItemsSource="{Binding Source={StaticResource collection_people}}"
              DisplayMemberPath="FirstName"/>

    <TextBox x:Name="tbFirstName" 
             Text="{Binding Path=SelectedItem.FirstName, ElementName=cbPerson, Mode=TwoWay,
                            UpdateSourceTrigger=Explicit}" 
             Width="Auto"/>

    <TextBox x:Name="tbLastName" 
             Text="{Binding Path=SelectedItem.LastName, ElementName=cbPerson, Mode=TwoWay, 
                            UpdateSourceTrigger=Explicit}" 
             Width="Auto"/>
</Grid>

Your click event handler be like,

private void btnSave_Click(object sender, RoutedEventArgs e)
{
    tbFirstName.GetBindingExpression(TextBox.TextProperty).UpdateSource();
    tbLastName.GetBindingExpression(TextBox.TextProperty).UpdateSource();
}