我在哪里可以捕获MVVM中的异常？ [英] Where do I catch Exceptions in MVVM?

问题描述

我的视图模型类有一个方法（不知道这是否是良好做法，或者视图模型是否应该是严格的属性和属性更改机制），它连接到一个服务。当然，我想在连接或断开连接时处理任何可能的WCF异常。

My view model class has a method (not sure if that is good practice or if view models are supposed to be strictly property and property changing mechanisms) that connects to a service. Of course I want to handle any possible WCF exceptions when connecting or disconnecting.

让我们使用未找到的端点，因为这是一个例外，我想要用户的关注。考虑粗略的代码示例：

Let's use endpoint not found as an example considering that is an exception that I would want to bring to the user's attention. Consider the rough code example:

public void Connect()
{
    ServiceClient proxy = null;
    try
    {
        proxy = new ServiceClient();
        proxy.Subscribe();
        // ...
    }
    catch(EndpointNotFoundException)
    {
        // should I do something here?
    }
    // .. other WCF related exception catches and a finally
}

是否可以直接在catch中调用System.Windows.MessageBox.Show（）被认为是好的做法，或者是否应该重新启动异常，这样我的WPF应用程序的另一层会捕获它？如果是这样，那么在哪里可以找到这样的例外？

Is it considered good practice to maybe invoke System.Windows.MessageBox.Show() directly within the catch or should I maybe rethrow the exception so another layer of my WPF application catches it? If so, where is the ideal place to catch such an exception?

推荐答案

我已经在我的MVVM客户端中处理异常捕获它们并将它们包装在任何 ViewModel 的 ErrorViewModel 属性中，捕获异常。

I've been handling exceptions in my MVVM client by catching them and wrapping them in an ErrorViewModel property of whatever ViewModel caught the exception.

我们假设一个ViewModel A 捕获EndpointNotFoundException。为了提出这个错误，我将异常包装在一个ErrorViewModel中，并将其分配给 A 的Error属性。

Let's say a ViewModel A catches the EndpointNotFoundException. To present this error, I wrap the Exception in an ErrorViewModel and assign that to A's Error property.

与 A 相关联的视图包含一个 ContentControl 绑定到 A 的错误属性。同时，我使用 DataTemplate 将错误视图与ErrorViewModel相关联。在该视图中，可见性由 A 的Error属性是否包含异常确定。

The View associated with A contains a ContentControl bound to A's Error property. Meanwhile, I use a DataTemplate to associate an Error View to the ErrorViewModel. In that View, Visibility is determined by whether or not A's Error property contains an exception.

所以 A 的视图包含一个错误消息仅在捕获异常时才会显示的视图，并且可以被用户忽略（错误消息View上的OK按钮调用 A 上的一个命令，该命令清除 A 的Error属性，从而将错误消息视图的可见性更改为 Collapsed ）。

So A's View contains an error-message View that will only appear when an exception is caught, and can be dismissed by the user (an OK button on the error-message View invokes a command on A that clears A's Error property, thereby changing the error-message View's visibility to Collapsed).

到目前为止，这似乎是一个很好的方法来保留适当的MVVM解耦。

Thus far, this seems to be a good approach that preserves proper MVVM decoupling.

希望有所帮助。有一种方式，老实说，我将WPF应用程序中的 System.Windows.MessageBox.Show（）视为最后的手段。为什么要放弃对UI的丰富控制，以支持那个老东西？说到这里，另一个弹出窗口实现方法。

Hope that helps. One way or another, honestly, I'd consider System.Windows.MessageBox.Show() in a WPF app as purely a last resort. Why give up rich control over the UI in favor of that old thing? Speaking of which, here's another popup-implementation approach.

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