WPF绑定改变椭圆填充颜色 [英] WPF Binding to change fill color of ellipse

问题描述

可能是一个简单的问题，但：

Probably a simple question but:

如何编程更改在XAML基于变量定义的椭圆的颜色

How do I programmatically change the color of an ellipse that is defined in XAML based on a variable?

一切我已经在绑定是以收藏，并列出我难道不会基于一个字符串变量的值设置它只是（和字面）读？串色=红颜色=＃FF0000

Everything I've read on binding is based on collections and lists -can't I set it simply (and literally) based on the value of a string variable? string color = "red" color = "#FF0000"

推荐答案

值得指出的是，转换器中的其他职位中引用的已存在的，这就是为什么你可以做<摆在首位在XAML;椭圆填充=红过夜。该转换器是 System.Windows.Media.BrushConverter ：

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");

的更有效的方法是使用完整的语法：

The more efficient way is to use the full syntax:

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

修改回应-1和评论：

上面的代码工作完全正常的代码的，这是原来的问题是问。您还的不的希望有一个的IValueConverter - 这些通常用于的结合的场景。 A 的TypeConverter 在这里是正确的解决方案（因为你是单向的字符串转换为刷）。请参见详情这篇文章。

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.

进一步修改（已重读阿维亚德的评论）：你不需要在XAML中明确使用的TypeConverter - 这是用于你。如果我写这篇文章在XAML：

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">

...那么运行时自动地使用 BrushConverter 打开字符串成一刷。这一XAML是基本上转变成等价的普通写法：

... 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>

所以，你是对的 - 你不能在XAML中使用它 - 但你并不需要到

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

即使你有你的作为填充想要的绑定的字符串值，你并不需要指定转换器手动。本次测试从Kaxaml：

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>

奇怪的是，你不能只用 StaticResource的山坳，仍然有这项工作 - 但与它结合，并自动使用 ValueConverter 转串入一个刷子

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.

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