XAML binding between controls?

Is it possible to bind between two controls? For example to be able to
do something like:

1. Have a button alter its width according to the current value of a
slider:

<Slider x:Name="MySlider" Minimum="10" Maximum="200" Value="120">
</Slider>

<Button Width="{Binding MySlider.Value}">
Click Me!
</Button>

or

2. Make a rectangle always have complete round left-right sides, no
matter its size:

<Rectangle Width="200" Height="50" RadiusX="{Binding Height/2}"
RadiusY="{Binding Height/2}">
</Rectangle>

Is this possible within XAML, or you just have to go code-behind too to
achieve this?

Thanks,
Cosmin.

1. Easy:

<Button Width="{Binding ElementName=MySlider, Path=Value}" ...

2.

I think the best way to do this is to write a converter - see the documentation
for System.Windows.Data.Binding and System.Windows.Data.IValueConverter.

- Doug

> Is it possible to bind between two controls? For example to be able to
> do something like:
>
> 1. Have a button alter its width according to the current value of a
> slider:
>
> <Slider x:Name="MySlider" Minimum="10" Maximum="200" Value="120">
> </Slider>
>
> <Button Width="{Binding MySlider.Value}">
> Click Me!
> </Button>
> or
>
> 2. Make a rectangle always have complete round left-right sides, no
> matter its size:
>
> <Rectangle Width="200" Height="50" RadiusX="{Binding Height/2}"
> RadiusY="{Binding Height/2}">
> </Rectangle>
> Is this possible within XAML, or you just have to go code-behind too
> to achieve this?
>
> Thanks,
> Cosmin.

> 1. Easy:
>
> <Button Width="{Binding ElementName=MySlider, Path=Value}" ...

Thanks, worked!

> 2.
>
> I think the best way to do this is to write a converter - see the documentation
> for System.Windows.Data.Binding and System.Windows.Data.IValueConverter.

I was thinking of implementing something like MultiplyConverter
together with MultiBinding, so what I would actually need is to pass
the height as the first parameter, and the value 0.5 as the second
parameter. This would actually give me half the height. But I don't
know how to do that, I'm having problems both in code and in markup.
Here's what I have so far:

--- XAML ---

<Rectangle
Grid.Column="0" Grid.Row="0" Grid.RowSpan="2"
Fill="#4171A6">
<Rectangle.RadiusY>
<MultiBinding Converter="{StaticResource conv}">
<MultiBinding.Bindings>
<Binding RelativeSource="{RelativeSource self}" Path="Height"
/>
<Binding Source="0.5" />
</MultiBinding.Bindings>
</MultiBinding>
</Rectangle.RadiusY>
<Rectangle.RadiusX>
<Binding RelativeSource="{RelativeSource self}" Path="RadiusY" />
</Rectangle.RadiusX>
</Rectangle>

However, with this markup, I get the following in the objects[] array
of the converter:
NaN, "0.5"; so I get an invalid number and a string... how can I obtain
doubles?

CosminB wrote:

> I was thinking of implementing something like MultiplyConverter
> together with MultiBinding, so what I would actually need is to pass
> the height as the first parameter, and the value 0.5 as the second
> parameter. This would actually give me half the height. But I don't
> know how to do that, I'm having problems both in code and in markup.

You don't need to use a MultiBinding. You can pass a parameter to your converter
via Binding's aptly named ConverterParameter property[1].

HTH,
Drew

[1] http://windowssdk.msdn.microsoft.com...rParameter.asp

Yep, that's an option too.
Is there a way to have my "0.5" value be passed as a double? Receiving
a string kindof messes code up.

CosminB wrote:

> Yep, that's an option too.
> Is there a way to have my "0.5" value be passed as a double? Receiving
> a string kindof messes code up.

Yep. I don't have time to check this code for you, but it should work. Basically
you need to use the expanded syntax for binding like so:

<!-- first, need to map BCL System namespace -->
<Window xmlns:system="clr-namespace:System;assembly=mscorlib" ....>

.....

<Rectangle.RadiusY>
<Binding RelativeSource="{RelativeSource self}" Path="Height">
<Binding.ConverterParameter>
<!-- use a Double from System -->
<systemouble>0.5</systemouble>
</Binding.ConverterParameter>
</Binding>
</Rectangle.RadiusY>

HTH,
Drew

___________________________________
Drew Marsh
Chief Software Architect
Mimeo.com, Inc. - http://www.mimeo.com
Microsoft C# / WPF MVP
Weblog - http://blog.hackedbrain.com/

Thanks, it worked.

I hope MS will put more effort into this area, it's hard to get things
done using this much markup and codebehind also. What I am trying to do
now is design a button template, I didn't know I would have to add code
behind only for this.

Also, I thought I could use a nested Bindings and MultiBindings, but
this isn't possible. I have designed two converters for multiplication
and addition. If nesting was possible, then it could have been possible
to calculate ((A+B)*C). But I only can A*B and A+B.

As it stands, XAML is quite poor when it comes to finetuning its
controls, I thought they did a good job, I am dissapointed. Or maybe
it's just that it's not enough documentation available, who knows...

Is this really messy?

return Convert.ToDouble(value) * Convert.ToDouble(parameter)

- Doug

> Yep, that's an option too.
> Is there a way to have my "0.5" value be passed as a double? Receiving
> a string kindof messes code up.

I am finding things that should be simply requiring more work and at the
moment its less intuitive, but I have used OpenLaszlo in the past its much
seems simpler to do some things and it can be doen in the markup

Have a look at the object orientation samples at

http://www.laszlosystems.com/lps/laszlo-in-ten-minutes/

Ok OpenLaszlo doesn't do all the things that Avalon does do, but I find it
much simpler and intuitive and can be done in the markup ..see below:

<canvas>

<simplelayout spacing="5"/>

<class name="box" height="100" width="100" bgcolor="red"/>

<class name="borderedbox" extends="box">
<attribute name="bordersize" value="3"/>
<view bgcolor="yellow"
x="${parent.bordersize}"
y="${parent.bordersize}"
width="${parent.width - parent.bordersize*2}"
height="${parent.height - parent.bordersize*2}"/>
</class>

<borderedbox/>
<borderedbox bordersize="6"/>
<borderedbox bordersize="9"/>

</canvas>


Regards
Ranj

"Douglas Stockwell" <doug@remove.11011.net> wrote in message
news:eca9ec38130b0e8c830e84bf3aae0@news.microsoft.com...
> Is this really messy?
>
> return Convert.ToDouble(value) * Convert.ToDouble(parameter)
>
> - Doug
>
>> Yep, that's an option too.
>> Is there a way to have my "0.5" value be passed as a double? Receiving
>> a string kindof messes code up.
>
>

I agree that these binding expressions would be useful. I wanted a feature
like this a some time ago, but I've come to live without it.

There could be many reasons why this isn't in WPF but a few that I can think
of would be:
- XAML/WPF is language neutral - how to choose / design an expression language?
- XAML is for tools: back in the time of Mini Languages (http://blogs.msdn.com/johngossman/ar...08/478593.aspx)
this may have been more likely

That said, I think it would be pretty simple to build an expression evaluator
(as a converter) for a MultiBinding. Unfortunately the markup wouldn't be
quite so elegant.

Something like:

<Border>
<Rectangle>
<Rectangle.Width>
<MultiBinding Converter="{StaticResource ExpressionConverter}" ConverterParameter="{0}
- {1} * 2">
<MultiBinding.Bindings>
<Binding Path="Parent.Width" />
<Binding Path="Parent.BorderThickness" />
</MultiBinding.Bindings>
</MultiBinding>
</Rectangle.Width>
</Rectangle>
</Border>

- Doug

> I am finding things that should be simply requiring more work and at
> the moment its less intuitive, but I have used OpenLaszlo in the past
> its much seems simpler to do some things and it can be doen in the
> markup
>
> Have a look at the object orientation samples at
>
> http://www.laszlosystems.com/lps/laszlo-in-ten-minutes/
>
> Ok OpenLaszlo doesn't do all the things that Avalon does do, but I
> find it much simpler and intuitive and can be done in the markup ..see
> below:
>
> <canvas>
>
> <simplelayout spacing="5"/>
>
> <class name="box" height="100" width="100" bgcolor="red"/>
>
> <class name="borderedbox" extends="box">
> <attribute name="bordersize" value="3"/>
> <view bgcolor="yellow"
> x="${parent.bordersize}"
> y="${parent.bordersize}"
> width="${parent.width - parent.bordersize*2}"
> height="${parent.height - parent.bordersize*2}"/>
> </class>
> <borderedbox/>
> <borderedbox bordersize="6"/>
> <borderedbox bordersize="9"/>
> </canvas>
>
> Regards
> Ranj
> "Douglas Stockwell" <doug@remove.11011.net> wrote in message
> news:eca9ec38130b0e8c830e84bf3aae0@news.microsoft.com...
>
>> Is this really messy?
>>
>> return Convert.ToDouble(value) * Convert.ToDouble(parameter)
>>
>> - Doug
>>
>>> Yep, that's an option too.
>>> Is there a way to have my "0.5" value be passed as a double?
>>> Receiving
>>> a string kindof messes code up.