MVVM疯狂：命令 [英] MVVM Madness: Commands

问题描述

我喜欢MVVM。我不喜欢它，但喜欢它。大多数的很有道理。但是，我继续读，鼓励你写了很多code，这样你可以写XAML和没有写任何code在code-后面的文章。

I like MVVM. I don't love it, but like it. Most of it makes sense. But, I keep reading articles that encourage you to write a lot of code so that you can write XAML and don't have to write any code in the code-behind.

让我给你举个例子。

最近我想在我的视图模型到ListView MouseDoubleClickEvent联播的命令。我不太知道如何做到这一点。幸运的是，谷歌有答案的一切。我发现下面的文章：

Recently I wanted to hookup a command in my ViewModel to a ListView MouseDoubleClickEvent. I wasn't quite sure how to do this. Fortunately, Google has answers for everything. I found the following articles:

• <一个href="http://blog.functionalfun.net/2008/09/hooking-up-commands-to-events-in-wpf.html">http://blog.functionalfun.net/2008/09/hooking-up-commands-to-events-in-wpf.html
• <一个href="http://joyfulwpf.blogspot.com/2009/05/mvvm-invoking-command-on-attached-event.html">http://joyfulwpf.blogspot.com/2009/05/mvvm-invoking-command-on-attached-event.html
• http://sachabarber.net/?p=514
• <一个href="http://geekswithblogs.net/HouseOfBilz/archive/2009/08/27/adventures-in-mvvm-ndash-binding-commands-to-any-event.aspx">http://geekswithblogs.net/HouseOfBilz/archive/2009/08/27/adventures-in-mvvm-ndash-binding-commands-to-any-event.aspx
• <一个href="http://marlongrech.word$p$pss.com/2008/12/13/attachedcommandbehavior-v2-aka-acb/">http://marlongrech.word$p$pss.com/2008/12/13/attachedcommandbehavior-v2-aka-acb/

• http://blog.functionalfun.net/2008/09/hooking-up-commands-to-events-in-wpf.html
• http://joyfulwpf.blogspot.com/2009/05/mvvm-invoking-command-on-attached-event.html
• http://sachabarber.net/?p=514
• http://geekswithblogs.net/HouseOfBilz/archive/2009/08/27/adventures-in-mvvm-ndash-binding-commands-to-any-event.aspx
• http://marlongrech.wordpress.com/2008/12/13/attachedcommandbehavior-v2-aka-acb/

虽然解决方案都有助于我的命令的理解，有问题。一些上述解决方案的渲染，因为附加的内部一个依赖属性后，一个共同的黑客WPF设计器无法使用; WPF设计无法找到它，但CLR可以。一些解决方案，没有允许多个命令到相同的控制。一些解决方案的不容许参数

While the solutions were helpful in my understanding of commands, there were problems. Some of the aforementioned solutions rendered the WPF designer unusable because of a common hack of appending "Internal" after a dependency property; the WPF designer can't find it, but the CLR can. Some of the solutions didn't allow multiple commands to the same control. Some of the solutions didn't allow parameters.

在尝试了几个小时，我就决定做这个：

After experimenting for a few hours I just decided to do this:

private void ListView_MouseDoubleClick(object sender, MouseButtonEventArgs e) {
    ListView lv = sender as ListView;
    MyViewModel vm = this.DataContext as MyViewModel;

    vm.DoSomethingCommand.Execute(lv.SelectedItem);
}

所以，MVVM较真的，请告诉我有什么错呢？但我还是能单位测试我的命令。这似乎很实用，但似乎违背的准则ZOMG ......你有code在code-后面!!!!请分享你的想法。

So, MVVM purists, please tell me what's wrong with this? I can still Unit test my command. This seems very practical, but seems to violate the guideline of "ZOMG... you have code in your code-behind!!!!" Please share your thoughts.

在此先感谢。

推荐答案

我认为故障出在纯度要求。设计模式，MVVM在内，都在工具箱中的工具，而不是你们自己结束。如果它更有意义的模型一个考虑周全的情况下的纯度突破（这显然看起来像你认为这种情况下），然后用该模型打破。

I think the fault lies in the purity requirement. Design patterns, MVVM included, are a tool in the toolbox, not an end unto themselves. If it makes more sense to break with the purity of the model for a well-considered case (and it clearly looks like you've considered this case), then break with the model.

如果为你的作品，你不相信这是一个不必要的维护负担，那么我会说，没有什么是错你做了什么。我认为你已经清楚地满足举证责任显示，这是一个合理的解决您的问题，尽管什么是纯MVVM的实现可能。

If that works for you, and you don't believe it's an undue maintenance burden, then I'd say that nothing is wrong with what you've done. I think that you've clearly met the burden of proof for showing that this is a reasonable solution to your problem in spite of what a pure MVVM implementation might be.

（我认为这种说法类似，为多范型语言的参数。当一个纯面向对象的方法可以适用，有时候做事情更实用的方法是比较合适的。虽然纯函数的方法可以应用，有时权衡显示，面向对象技术是多值得的。）

(I consider this argument similar to the arguments for multiparadigm languages. While a Pure OO approach can be applied, sometimes doing things in a more functional way is more appropriate. While a Pure Functional approach can be applied, sometimes the trade offs show that OO techniques are more than worth the while.)

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