如何绑定只读 WPF 控件属性(例如 ActualWidth)，以便在视图模型中可以访问其值? [英] How to bind a read-only WPF control property (eg ActualWidth) so its value is accessible in the view model?

问题描述

我想将控件的只读属性绑定到我的视图模型，以便该值在视图模型中可用.

I want to bind a read-only property of a control to my view model so that the value is available in the view model.

这样做的最佳方法是什么?

What is the best way of doing this?

例如，我想将 ActualWidth 绑定到我的视图模型中的一个属性.宽度值是由 WPF 使用其布局逻辑生成的，因此我无法在我的视图模型中生成此值并将其推送到控件属性，这通常是这种情况.相反，我需要让 WPF 生成值并将其推送到视图模型.

For example I'd like to bind ActualWidth to a property in my view model. The width value is generated by WPF using its layout logic so I can't generate this value in my view model and push it to the control property, as would normally be the case. Instead I need to have WPF generate the value and push it to the view model.

我只想使用 Mode=OneWayToSource，但这不适用于只读属性:

I would just use Mode=OneWayToSource, but this doesn't work for read-only properties:

  <Border
      ...
      ActualWidth="{Binding MyDataModelWidth, Mode=OneWayToSource}"
      >
      ... child controls ...
  </Border>

我目前的做法是处理边框的SizeChanged，代码隐藏将值插入到视图模型中，但这感觉不太对.

The way I am doing it currently is to handle SizeChanged for the border and the code-behind plugs the value into the view model, but this doesn't feel quite right.

有人已经解决了这个问题吗?

Has anyone already solved this problem?

更新:我的问题实际上是这个问题的重复:将只读 GUI 属性推回 ViewModel

UPDATE: My question is effectively a duplicate of this one: Pushing read-only GUI properties back into ViewModel

推荐答案

描述了为什么这不起作用的实际问题 此处.

The actual problem as to why this is not working is described here.

但是，创建抛出设置器以通过验证的给定解决方案不适用于您的情况.

However, the given solution to create a throwing setter to pass the validation would not work in your case.

我认为在 ViewModel 上调用一个方法是可以的.如果那是让您感到困扰的部分代码，也许您可​​以使用交互性来调用基于事件触发器 (SizeChanged) 的方法.

I think it's ok to call a method on the ViewModel. If that's the code behind part that bugs you, perhaps you can use interactivity to call a method based on an event trigger (SizeChanged).

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