当绑定到Image.Source时，Xaml如何创建BitmapImage值转换的字符串？ [英] How does Xaml create the string to BitmapImage value conversion when binding to Image.Source?

问题描述

我正在创建一个 Image.Source - String 在代码中绑定如下：

I'm creating an Image.Source-String binding in code like:

var newBinding = new System.Windows.Data.Binding()
  {
    Path = new PropertyPath("MyImageUrl")
  };
BindingOperations.SetBinding(attachedObject, Image.SourceProperty, newBinding);

此方法适用于例如 TextBlock.TextProperty - String 绑定，但对于 Image.Source - String 我理想地希望 Binding 自动为我插入一个转换 - 与我使用的Xaml绑定时一样：

This approach works well for, for example, TextBlock.TextProperty-String bindings, but for the Image.Source-String I ideally would like the Binding to automatically insert a conversion for me - in the same way that the Xaml binding does when I use:

<Image Source="{Binding ImageUrl}" />

我意识到我可以添加自己的转换器来模拟Xaml绑定行为，但我想看看是否有一些方法可以做到Xaml所做的一切。

I realise I can add my own converter to mimic the Xaml binding behaviour, but I'd like to see if there's some way to do exactly what the Xaml does.

有没有办法获得新的绑定在基于代码的绑定评估期间自动添加自己的字符串 - > BitmapImage ValueConverter

Is there some way to get the new Binding to automatically add it's own string->BitmapImage ValueConverter during the code-based bind evaluation?

推荐答案

System.Windows.Media.ImageSource有一个 TypeConverterAttribute

System.Windows.Media.ImageSource has a TypeConverterAttribute

[TypeConverter(typeof(ImageSourceConverter))]

绑定将寻找这个并使用转换器自动。

The binding will look for this and use the converter automatically.

如果您查看 ImageSourceConverter ，您可以看到可以转换的类型：

If you look at the ImageSourceConverter you can see what types it can convert from:

if (sourceType == typeof(string) || 
    sourceType == typeof(Stream) || 
    sourceType == typeof(Uri) || 
    sourceType == typeof(byte[]))
{
    return true;
}

为了模仿此过程，您必须添加一个 TypeConverterAttribute 对于绑定的属性的类型。

In order to mimic this process, you must add a TypeConverterAttribute on the Type of the property being bound to.

您可以通过以下方式执行此操作：1.控制类型，或2.使用 TypeDescriptor 在运行时添加属性。有关于此此处的问题。

You can do this by 1. controlling the type, or 2. use the TypeDescriptor at runtime to add the attribute. There's a question about this here.

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