RC0 Error: TextBox is locked and does not fire MouseLeftButtonDown event

09-28-2008 5:49 AM |

 During my migration to RC0 I discovered a strange new behaviour of the TextBox user control:

1. Whenever I set its visibility attribute to "collapsed" and "visible" again, the text content is locked, meaning the user cannot change it any longer. I found a workaround by removing the text box from the children collection of its parent element and adding it again.
2. The MouseLeftButtonDown (defined within XAML) doesn't fire any longer without throwing any error / exception. I found a workaround by replacing this event with a GotFocus event.
   

 Has anybody an idea, why this strange new behaviour occurs and how it might be fixed in other ways than I did?

Re: RC0 Error: TextBox is locked and does not fire MouseLeftButtonDown event

09-28-2008 9:21 AM |

Update: It seems like the MouseLeftButtonDown event is not fired by the Button user controls either. Maybe all user controls are affected?

Re: RC0 Error: TextBox is locked and does not fire MouseLeftButtonDown event

09-30-2008 2:22 AM |

Hi,

I cannot reproduce this problem. Could you post a demo project that can reproduce this problem?

Re: RC0 Error: TextBox is locked and does not fire event

09-30-2008 7:34 AM |

 Hi,

I can reprocuce the second error:

The MouseLeftButtonDown event doesn't fire, if the TextBox contains Text. Clicking near the TextBox Border (mouse icon: Arrow) works fine. Clicking inside the TextBox (mouse icon has changed) fails.

<UserControl x:Class="TBClickBugRepro.Page"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Width="400" Height="300">
    <Grid x:Name="LayoutRoot" Background="White">
      <TextBox x:Name="Test" Text="123" MouseLeftButtonDown="Test_MouseLeftButtonDown" Height="20" Width="Auto"></TextBox>
    </Grid>
</UserControl>

Re: RC0 Error: TextBox is locked and does not fire event

10-01-2008 10:25 AM |

Thanks a lot to Stefan, who already reproduced the second error.

However, I was not able to reproduce the first error, since it did not occur in any new Silverlight project I created. The App where it occurs is a bit complex , so it might take some time to find the cause. In the meantime I am happy with my workaround.

The first error however might be severe, if it really affects all Silverlight user controls in RC0.

Is it really an error caused by the release of RC0? If so, will it be fixed?

Re: RC0 Error: TextBox is locked and does not fire event

10-01-2008 5:34 PM |

I agree. As long as the cursor is an Insert Cursor (I-beam), the MouseLeftButtonDown or MouseLeftButtonUp events do not fire. If you move to the border of the TextBox where the cursor changes back to the standard selection arrow, the MouseLeftButtonDown event fires and the Sender value sent to the event handler is TextBox.

This doesn't seem like it is working properly.

Re: RC0 Error: TextBox is locked and does not fire event

10-01-2008 7:16 PM |

This is by design and consistent with the behavior in WPF. The TextBox marks the mouse down/up events as handled and thus won't bubble them up any further.

You can get the mouse events by deriving from TextBox like this:

public class TextBox2 : TextBox
{
    protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
    {
        base.OnMouseLeftButtonDown(e);
    }

    protected override void OnMouseLeftButtonUp(MouseButtonEventArgs e)
    {
        base.OnMouseLeftButtonUp(e);
    }
}

Thanks, Stefan Wick

Re: RC0 Error: TextBox is locked and does not fire event

10-01-2008 8:59 PM |

StefanWick:

This is by design and consistent with the behavior in WPF. The TextBox marks the mouse down/up events as handled and thus won't bubble them up any further.

Thanks, Stefan Wick

Re: RC0 Error: TextBox is locked and does not fire event

10-02-2008 1:17 AM |

It actually is consistent. Further down in the reference topic there is an "Important Note" that talks about this.

http://msdn.microsoft.com/en-us/library/system.windows.uielement.mouseleftbuttondown(VS.95).aspx

"Certain control classes (for example Button) provide control-specific handling for mouse events such as MouseLeftButtonDown. The control-specific handling typically involves handling the event at a class level rather than at the instance level, and marking the MouseLeftButtonDown event data's Handled value as true such that the event cannot be handled by instances of the control class, nor by other objects anywhere further along the event route. In the case of Button, the class design does this so that the Click event can be raised instead."

This is exactly what happens here in the TextBox case. The TextBox control marks the events as handled. As I pointed out before, derived classes do receive the events - and they can set the Handled property back to false, then the mouse up/down events will fire on TextBox control. Here is how you do this:  

public class TextBox2 : TextBox
{
    protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
    {
        base.OnMouseLeftButtonDown(e);
        e.Handled = false;
    }

    protected override void OnMouseLeftButtonUp(MouseButtonEventArgs e)
    {
        base.OnMouseLeftButtonUp(e);
        e.Handled = false;
    }
}

Thanks, Stefan Wick

Re: RC0 Error: TextBox is locked and does not fire event

10-02-2008 1:37 AM |

I disagree that this is consistent. In my opinion it's not consistent when the event is sometimes handled by the control and sometimes not.

I wanted to use this event to clear the Text in a TextBox, when the user clicks inside the Box. Your solution or using the GotFocus event works fine for me.

Thanks,

Re: RC0 Error: TextBox is locked and does not fire event

10-18-2008 8:09 AM |

But this breaks things for my project.....:(

Re: RC0 Error: TextBox is locked and does not fire event

10-18-2008 11:16 AM |

Can you explain the scenario that this breaks? Does deriving your own class from TextBox not un-break it for you?

Thanks, Stefan Wick