Binding.UpdateSourceTrigger

Question

Hi 

what about Binding.UpdateSourceTrigger? It seems like controls can only bind when they lose their focus. WPF allows also binding in realtime (UpdateSourceTrigger=PropertyChange). Is this possible with Silverlight?

Regards
Marco Buerckel

Answer 1

Nevermind, just built an extension that does the job. Anyway, it would be great to see that feature within the next beta...

Regards
Marco Buerckel

Answer 2

How did you achieve this?

 

Thanks,

Andy

 

Answer 3

Hi,

I'd be very interested in knowing how you did this. Would you mind posting the code to your extension, or telling us how you faked the UpdateSourceTrigger?

Thanks,

Romain

Answer 4

Hi Romain and Andy,

I just created one small sample for you guys. I make it works only for Textbox. You guys need to customize it based on your requirement.

UpdateSourceTriggerHelper - Attached Properties

 public class UpdateSourceTriggerHelper
    {
        public static readonly DependencyProperty UpdateSourceTriggerProperty =
            DependencyProperty.RegisterAttached("UpdateSourceTrigger", typeof(bool), typeof(UpdateSourceTriggerHelper),
                                                new PropertyMetadata(OnUpdateSourceTriggerChanged));

        public static bool GetUpdateSourceTrigger(DependencyObject d)
        {
            return (bool)d.GetValue(UpdateSourceTriggerProperty);
        }


        public static void SetUpdateSourceTrigger(DependencyObject d, bool value)
        {
            d.SetValue(UpdateSourceTriggerProperty, value);
        }

        private static void OnUpdateSourceTriggerChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            TextBox textBox = d as TextBox;
            if ((bool)e.OldValue)
            {
                textBox.TextChanged -= (s, arg) => {
                       
                 };
            }
            if ((bool)e.NewValue)
            {
                textBox.TextChanged += (s, arg) => {
                    var c = findFocusableControl(textBox);
                    if (c != null)
                    {
                        c.Focus();
                    }
                    textBox.Focus();
                 };
            }
        }

        private static Control findFocusableControl(Control control)
        {
           var ctl = VisualTreeHelper.GetParent(control);
           if ((ctl as Control) != null)
           {
               return ctl as Control;
           }
           else
           {
               int childrenCount = VisualTreeHelper.GetChildrenCount(ctl);
               for (int i = 0; i < childrenCount; i++)
               {
                   var c = VisualTreeHelper.GetChild(ctl, i) as Control;
                   if ((c != null) && (c != control))
                   {
                       return c;
                   }
               }
           }
           return null;
        }
    }

 

Usage :

<UserControl x:Class="UpdateSourceTriggerExtDemo.Page"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:UpdateSourceTriggerExtDemo"        
    Width="400" Height="300">
    <Grid x:Name="LayoutRoot" Background="White">
        <StackPanel>
            <TextBox x:Name="nameTextbox" Height="25" Width="100" Margin="5" Text="{Binding Name, Mode=TwoWay}"
                    local:UpdateSourceTriggerHelper.UpdateSourceTrigger="True" />
            <TextBox x:Name="addressTextbox" Height="25" Width="100" Margin="5" Text="{Binding Address, Mode=TwoWay}"
                    local:UpdateSourceTriggerHelper.UpdateSourceTrigger="False" />
            <TextBox x:Name="phoneTextbox" Height="25" Width="100" Margin="5" Text="{Binding Phone, Mode=TwoWay}"
                     />
            <Button Height="25" Width="100" Margin="5" Content="Save" />
        </StackPanel>
       
       
    </Grid>
</UserControl>

Answer 5

Thanks mchlsync!

This is a great way of automating the focus trick. I just have to do some research on how to set attached properties programmatically (my TextBox is created in the code), but it looks very promising!

 

Answer 6

There's also another solution than using the focus trick. Try it via updating the BindingSource directly:

 http://www.thomasclaudiushuber.com/blog/2009/07/17/here-it-is-the-updatesourcetrigger-for-propertychanged-in-silverlight/

 

Answer 7

 I have created a workaround using behaviors. Here is the blogpost, and you can download the code as well:

Binding update on TextBox.TextChanged event using Behaviors

Answer 8

http://forums.silverlight.net/forums/p/19746/335602.aspx

Answer 9

Were you able to set attached properties programmatically? Can you please share with me the sample?

Answer 10

Of course you can set them programmatically. Use the SetValue-Method inherited from DependencyObject.

E.g.

myTextBox.SetValue(BindingHelper.UpdateSourceOnChangeProperty,true);