MVVM模式违规:MediaElement.Play() [英] MVVM pattern violation: MediaElement.Play()

问题描述

我了解ViewModel不应该对View有任何了解，但是除了在ViewModel中引用View(或直接引用MediaElement)之外，如何从ViewModel调用MediaElement.Play()方法?
其他(链接的)问题:如何在不违反MVVM模式的情况下从ViewModel管理View控件的可见性?

I understand that ViewModel shouldn't have any knowledge of View, but how can I call MediaElement.Play() method from ViewModel, other than having a reference to View (or directly to MediaElement) in ViewModel?
Other (linked) question: how can I manage View's controls visibility from ViewModel without violating MVVM pattern?

推荐答案

1)不要从视图模型中调用Play().而是在视图模型中引发一个事件(例如PlayRequested)，然后在视图中侦听此事件:

1) Do not call Play() from the view model. Raise an event in the view model instead (for instance PlayRequested) and listen to this event in the view:

视图模型:

public event EventHandler PlayRequested;
...
if (this.PlayRequested != null)
{
    this.PlayRequested(this, EventArgs.Empty);
}

视图:

ViewModel vm = new ViewModel();
this.DataContext = vm;
vm.PlayRequested += (sender, e) =>
{
    this.myMediaElement.Play();
};

2)您可以在视图模型中公开一个布尔属性，并将控件的Visibility属性绑定到该属性.由于Visibility是类型Visibility而不是bool，因此您必须使用转换器.

2) You can expose in the view model a public boolean property, and bind the Visibility property of your controls to this property. As Visibility is of type Visibility and not bool, you'll have to use a converter.

您可以找到这种转换器的基本实现这里. 此相关问题可能也对您有帮助.

You can find a basic implementation of such a converter here. This related question might help you too.

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