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WPF Binding to change fill color of ellipse

Answer 1

+1 A:

Leigh Shayler 2010-03-16 00:13:55

This would be correct if you'd convert to a `Brush` object instead of a `Color` object. Simply using a `BrushConverter` instead of a `ColorConverter` should do the trick. Although I think you need an instance of that converter, the `ConvertFromString` method is not static, is it?

Aviad P. 2010-03-16 00:17:14

If you bind using a color then you are free to use the Colors class which has intellisense on the color names as well.

Leigh Shayler 2010-03-16 23:18:51

These converters *already exist*....

Dan Puzey 2010-03-16 23:32:23

Answer 2

A:

It's worth pointing out that the converter the other posts reference already exists, which is why you can do <Ellipse Fill="red"> in xaml in the first place. The converter is System.Windows.Media.BrushConverter:

        BrushConverter bc = new BrushConverter();
        Brush brush = (Brush) bc.ConvertFrom("Red");

The more efficient way is to use the full syntax:

myEllipse.Fill = new SolidColorBrush(Colors.Red);

EDIT in response to -1 and comments:

The code above works perfectly fine in code, which is what the original question was asking about. You also don't want an IValueConverter - these are typically used for binding scenarios. A TypeConverter is the right solution here (because you're one-way converting a string to a brush). See this article for details.

Further edit (having reread Aviad's comment): you don't need to explicitly use the TypeConverter in Xaml - it's used for you. If I write this in Xaml:

<Ellipse Fill="red">

... then the runtime automagically uses a BrushConverter to turn the string literal into a brush. That Xaml is essentially converted into the equivalent longhand:

<Ellipse>
  <Ellipse.Fill>
     <SolidColorBrush Color="#FFFF0000" />
  </Ellipse.Fill>             
</Ellipse>

So you're right - you can't use it in Xaml - but you don't need to.

Even if you had a string value that you wanted to bind in as the fill, you don't need to specify the converter manually. This test from Kaxaml:

<Page
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:s="clr-namespace:System;assembly=mscorlib">
  <Page.Resources>
    <s:String x:Key="col">Red</s:String>
  </Page.Resources>

  <StackPanel>  
    <Ellipse Width="20" Height="20" Fill="{Binding Source={StaticResource col}}" />
  </StackPanel>
</Page>

Strangely, you can't just use the StaticResource col and still have this work - but with the binding it and automatically uses the ValueConverter to turn the string into a brush.

Dan Puzey 2010-03-16 23:32:00

This does not answer the question, the `BrushConverter` does not implement `IValueConverter` so you cannot use it in XAML.

Aviad P. 2010-03-17 08:59:27

Edited my answer rather than replying here because I think it's worth pointing out why I'm right in detail...

Dan Puzey 2010-03-17 10:07:12

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WPF Binding to change fill color of ellipse

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