How to force property binding

Question

How to force property binding

BitSmithy 2,206

Hello,

I have binding defined in xaml:

                   Canvas.Left= "{Binding ElementName=ucUESelector, Path=RenderTransformOrigin, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource ThRotationCenterPointConverter}, ConverterParameter=CanvasX}"
                   Canvas.Top= "{Binding ElementName=ucUESelector, Path=RenderTransformOrigin, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource ThRotationCenterPointConverter}, ConverterParameter=CanvasY}"

Now I want force app to trigger this binding code behind in case that binded proprty hasnt changed and binding isnt trigered automatically.

Is such possiblity?

Junjie Zhu - MSFT 21,646 Reputation points

2023-08-24T03:45:47.21+00:00

Hi @BitSmithy ,

Welcome to Microsoft Q&A!

I want force app to trigger this binding code behind

Could you please explain what your scenario is? Is there something wrong with the trigger now?

Thank you.
BitSmithy 2,206 Reputation points

2023-08-28T08:17:25.94+00:00

This trigger triggers when RenderTransformOrigin is changed, but in the converter is written logic, where result is dependat from curent RenderTransformOrigin and curent Width and Height. I want to manually triger the binding when Width or Height is changing. These changes are controled code behind.
Junjie Zhu - MSFT 21,646 Reputation points

2023-08-28T09:26:01.5366667+00:00

To help us further check the problem for you, could you please provide more code snippets that can reproduce the scenario you mentioned?

BitSmithy 2,206

The code is very complex, I put here part of the code involved with asked logic.

XAML:

            <Thumb x:Name="thTransformOrigin"                   
                   
                   Width="10" Height="10" Background="Red"                   
                   CanDrag="True"
                   CornerRadius="4"
                   Visibility="Collapsed"
                   
                   Canvas.Left= "{Binding ElementName=ucUESelector, Path=RenderTransformOrigin, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource ThRotationCenterPointConverter}, ConverterParameter=CanvasX}"
                   Canvas.Top= "{Binding ElementName=ucUESelector, Path=RenderTransformOrigin, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource ThRotationCenterPointConverter}, ConverterParameter=CanvasY}"            
                   
                   PointerEntered="Thumb_PointerEntered"
                   PointerExited="Thumb_PointerExited"
                   PointerCanceled="Thumb_PointerCanceled"
                   
                   
                   
                   ></Thumb>

XAML resources

        <local:ThumbRotationCenterPointConventer x:Key="ThRotationCenterPointConverter" FE="{x:Bind ucUESelector}"/>

Converter:

    public class ThumbRotationCenterPointConventer : IValueConverter
    {
        public FrameworkElement FE { get; set; }

        public object Convert(object value, Type targetType,
            object parameter, string language)
        {
            //object render transform
            if (value is Point rto)
            {
                if ((string)parameter == "CanvasX")
                {
                    return rto.X * FE.Width;
                }
                else if ((string)parameter == "CanvasY")
                {
                    return rto.Y * FE.Height;
                }
                else
                    return 0;
            }
            else
                return 0;
        }

        // ConvertBack is not implemented for a OneWay binding.
        public object ConvertBack(object value, Type targetType,
            object parameter, string language)
        {
            if (value is Point rto)
            {                
                if ((string)parameter == "CanvasX")
                {
                    return rto.X * FE.Width;
                }
                else if ((string)parameter == "CanvasY")
                {
                    return rto.Y * FE.Height;
                }
                else
                    return 0;
            }
            else
                return 0;
        }
    }

Junjie Zhu - MSFT 21,646 Reputation points

2023-08-30T10:03:00.44+00:00

Hello @BitSmithy ,

I tested your code, if you need to trigger manually, you need to use UpdateSourceTrigger=Explicit. Maybe you can provide the relevant code of ucUESelector, we can try to find solutions from other directions.
BitSmithy 2,206 Reputation points

2023-08-30T12:34:20.1166667+00:00
UpdateSourceTrigger=Explicit is no option.

I know solution from the other direction, but it needs more code.

But there are something like

Bindings.Update()

this.Bindings.Update()

I dont know how they works, but maybe they could help.

Could you explain like option 1 and 2 works? Google and Bing doesnt provide too much info about Bindings.
BitSmithy 2,206 Reputation points

2023-08-31T09:23:03.59+00:00

I was thinking that there is any command to force binding, but this answer solves my problem too.
Junjie Zhu - MSFT 21,646 Reputation points

2023-08-31T09:32:36.3666667+00:00

Hi @BitSmithy ,

Bindings.Update() is not supported in UWP. At present, there is no way to force binding. In fact, you want to achieve multiple triggers, but currently UWP only supports binding one variable.

I converted my solution into an answer. If it helps you resolve the problem, please mark it as accepted.

Thank you.

Accepted answer

0 additional answers

Your answer

Junjie Zhu - MSFT 21,646 Reputation points

2023-08-24T03:45:47.21+00:00

Hi @BitSmithy ,

Welcome to Microsoft Q&A!

I want force app to trigger this binding code behind

Could you please explain what your scenario is? Is there something wrong with the trigger now?

Thank you.
BitSmithy 2,206 Reputation points

2023-08-28T08:17:25.94+00:00

This trigger triggers when RenderTransformOrigin is changed, but in the converter is written logic, where result is dependat from curent RenderTransformOrigin and curent Width and Height. I want to manually triger the binding when Width or Height is changing. These changes are controled code behind.
Junjie Zhu - MSFT 21,646 Reputation points

2023-08-28T09:26:01.5366667+00:00

To help us further check the problem for you, could you please provide more code snippets that can reproduce the scenario you mentioned?
BitSmithy 2,206 Reputation points

2023-08-29T08:55:51.14+00:00

The code is very complex, I put here part of the code involved with asked logic.

XAML:

<Thumb x:Name="thTransformOrigin" Width="10" Height="10" Background="Red" CanDrag="True" CornerRadius="4" Visibility="Collapsed" Canvas.Left= "{Binding ElementName=ucUESelector, Path=RenderTransformOrigin, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource ThRotationCenterPointConverter}, ConverterParameter=CanvasX}" Canvas.Top= "{Binding ElementName=ucUESelector, Path=RenderTransformOrigin, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource ThRotationCenterPointConverter}, ConverterParameter=CanvasY}" PointerEntered="Thumb_PointerEntered" PointerExited="Thumb_PointerExited" PointerCanceled="Thumb_PointerCanceled" ></Thumb>

XAML resources

<local:ThumbRotationCenterPointConventer x:Key="ThRotationCenterPointConverter" FE="{x:Bind ucUESelector}"/>

Converter:

public class ThumbRotationCenterPointConventer : IValueConverter { public FrameworkElement FE { get; set; } public object Convert(object value, Type targetType, object parameter, string language) { //object render transform if (value is Point rto) { if ((string)parameter == "CanvasX") { return rto.X * FE.Width; } else if ((string)parameter == "CanvasY") { return rto.Y * FE.Height; } else return 0; } else return 0; } // ConvertBack is not implemented for a OneWay binding. public object ConvertBack(object value, Type targetType, object parameter, string language) { if (value is Point rto) { if ((string)parameter == "CanvasX") { return rto.X * FE.Width; } else if ((string)parameter == "CanvasY") { return rto.Y * FE.Height; } else return 0; } else return 0; } }
Junjie Zhu - MSFT 21,646 Reputation points

2023-08-30T10:03:00.44+00:00

Hello @BitSmithy ,

I tested your code, if you need to trigger manually, you need to use UpdateSourceTrigger=Explicit. Maybe you can provide the relevant code of ucUESelector, we can try to find solutions from other directions.
BitSmithy 2,206 Reputation points

2023-08-30T12:34:20.1166667+00:00

UpdateSourceTrigger=Explicit is no option.

I know solution from the other direction, but it needs more code.

But there are something like

Bindings.Update()

this.Bindings.Update()

I dont know how they works, but maybe they could help.

Could you explain like option 1 and 2 works? Google and Bing doesnt provide too much info about Bindings.
BitSmithy 2,206 Reputation points

2023-08-31T09:23:03.59+00:00

I was thinking that there is any command to force binding, but this answer solves my problem too.
Junjie Zhu - MSFT 21,646 Reputation points

2023-08-31T09:32:36.3666667+00:00

Hi @BitSmithy ,

Bindings.Update() is not supported in UWP. At present, there is no way to force binding. In fact, you want to achieve multiple triggers, but currently UWP only supports binding one variable.

I converted my solution into an answer. If it helps you resolve the problem, please mark it as accepted.

Thank you.

Answer 1

Hello @BitSmithy ,

If it also uses bind, maybe we can modify the value of RenderTransformOrigin in the ucUESelector_SizeChanged event to trigger UpdateSourceTrigger=PropertyChanged. What I mean is changing an extremely small value(If it is less than 0.0000001, it will not trigger) so that it has little impact on rendering.

int count = 0;
private void ucUESelector_SizeChanged(object sender, SizeChangedEventArgs e)
{
             
    if (count %2 == 0)
    {
       Renderpoint = new Point(Renderpoint.X + 0.0000001, Renderpoint.Y);
    }
    else
    {
        Renderpoint = new Point(Renderpoint.X - 0.0000001, Renderpoint.Y);
    }
    count++;
}

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How to force property binding

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