不建议在MVVM应用程序中使用MessageBox？ [英] MessageBox is not recommended in MVVM applications?

问题描述

当我问到如何在MVVM中实现对话框时，有人建议我阅读此线程：

When I asked about how to implement a dialog in MVVM someone advised me to read this thread:

MVVM，DialogService和对话框结果

在视图模型中，该对话框被称为这样：

In the view model, the dialog is called in this way:

var dialog = new DialogViewmodel();
var result = _dialogservice.ShowDialog("My Dialog", dialog);

if(result.HasValue && result.Value)
{
    //accept true
}
else
{
    //Cancel or false
}

但这与使用messageBox不同吗

But is this different than using a messageBox in this way?

DialogResult result = MessageBox.Show("Hello");

if(result == DialgoResult-OK)
{
    //accept true
}
else
{
    //Cancel or false
}

在第二种情况下，我使用MessageBox代替自定义对话框，所以我看不出有什么区别。

In this second case, I use MessageBox instead of the custom dialog, so I don't see any difference.

无论如何，在许多情况下，我读到在MVVM应用程序中使用MessageBox是一个坏主意，因为它会破坏MVVM模式。但是，如果确实如此，我看不到第一种解决方案不会破坏MVVM模式，而第二种解决方案不会破坏它。

Anyway, in many cases I have read that to use a MessageBox in MVVM application it is a bad idea because it breaks the MVVM pattern. But really if this is true, I don't see how the first solution doesn't break the MVVM pattern and the second one breaks it.

推荐答案

MVVM模式的基本思想是关注点分离。视图模型不应该知道如何处理或显示对话框。为什么？以下是一些原因：

The basic idea of the MVVM pattern is the separation of concerns. The View Model should not know how to handle or present a dialog. Why? Here are some reasons:

• 测试视图模型：不需要对话框（假设您一直需要单击对话框）


• 创建GUI应用程序的控制台应用程序（对话框应在控制台中显示，而不是作为弹出框显示）


• 需要更改对话框的设计（假设您需要更改所有MessageBox调用）


• ...

• Testing your View Model: No dialogs are desired (Imagine you need to click dialogs all the time)
• Creating a console application of a GUI application (The dialogs should be shown in console not as popup boxes)
• It is required to change the design of your dialogs (Imagine you need to change all MessageBox calls)
• ...

解决方案：
通过为对话框实现定义良好的界面来使用依赖项注入。您可以在此答案。

结果：
调用 _dialogservice.ShowDialog 可能只是 MessageBox.Show 的包装，但也可能是控制台应用程序或调试日志中控制台中的某些对话框。在测试期间。因此，代码与任何演示文稿都完全分开。

Result: Calling _dialogservice.ShowDialog is maybe only a wrapper of MessageBox.Show but could also be a some dialog in a console in a console application or debug log during testing. So the code is well separated of any presentation.

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