在ViewModel应该如何关闭该窗体？ [英] How should the ViewModel close the form?
问题描述
我想学习WPF和MVVM问题，但遇到了阻碍。
这个问题是相似但不完全相同这一个（处理，对话功能于WPF -with-MVVM） ...
I'm trying to learn WPF and the MVVM problem, but have hit a snag. This question is similar but not quite the same as this one (handling-dialogs-in-wpf-with-mvvm)...
我有一个登录的形式书面使用MVVM模式。
I have a "Login" form written using the MVVM pattern.
这形式有一个ViewModel持有的用户名和密码，这必将对使用正常的数据绑定在XAML视图。
它也有一个登录，这是绑定到登录按钮的形式，阿甘使用正常的数据绑定的命令。
This form has a ViewModel which holds the Username and Password, which are bound to the view in the XAML using normal data bindings. It also has a "Login" command which is bound to the "Login" button on the form, agan using normal databinding.
在登录命令火灾，它调用其中熄灭，并通过网络将数据发送到登录视图模型的函数当此功能完成后，有2个动作：
When the "Login" command fires, it invokes a function in the ViewModel which goes off and sends data over the network to log in. When this function completes, there are 2 actions:
-
登录无效 - 我们只是显示一个MessageBox所有的罚款
The login was invalid - we just show a MessageBox and all is fine
登录是有效的，我们需要关闭登录窗体，并将它作为返回true的的DialogResult ...
The login was valid, we need to close the Login form and have it return true as its DialogResult...
问题是，视图模型一无所知实际的看法，所以它怎么能关闭视图并告诉它返回一个特定的DialogResult？我能沾些code在codeBehind，和/或通过向视图模型通过查看，但看起来它会破坏MVVM整点完全...
The problem is, the ViewModel knows nothing about the actual view, so how can it close the view and tell it to return a particular DialogResult?? I could stick some code in the CodeBehind, and/or pass the View through to the ViewModel, but that seems like it would defeat the whole point of MVVM entirely...
在最后我只是违反了MVVM模式的纯洁，不得不查看发布关闭事件，暴露出一个关闭方法。然后，视图模型只是调用 view.Close 。该视图只通过一个接口知并通过IOC容器接线，所以没有可测试性和可维护性会丢失。
In the end I just violated the "purity" of the MVVM pattern and had the View publish a Closed event, and expose a Close method. The ViewModel would then just call view.Close. The view is only known via an interface and wired up via an IOC container, so no testability or maintainability is lost.
这似乎相当愚蠢的接受的答案是在-5票！虽然我很清楚那一个得到通过而被纯解决问题的好感情，当然我不是认为200行的事件，命令和行为，只是为了避免单行法的唯一的模式和纯洁的名字有点可笑......
It seems rather silly that the accepted answer is at -5 votes! While I'm well aware of the good feelings that one gets by solving a problem while being "pure", Surely I'm not the only one that thinks that 200 lines of events, commands and behaviors just to avoid a one line method in the name of "patterns" and "purity" is a bit ridiculous....
推荐答案
我的灵感来自于<一个href=\"http://stackoverflow.com/questions/501886/wpf-mvvm-newbie-how-should-the-viewmodel-close-the-form/1153602#1153602\">Thejuan's回答写一个简单的附加属性。没有风格，没有触发;相反，你可以这样做：
I was inspired by Thejuan's answer to write a simpler attached property. No styles, no triggers; instead, you can just do this:
<Window ...
xmlns:xc="clr-namespace:ExCastle.Wpf"
xc:DialogCloser.DialogResult="{Binding DialogResult}">
这几乎是那样干净，如果WPF队右侧得到它，并在第一时间做出的DialogResult一个依赖属性。只要把一个布尔？在你的视图模型的DialogResult 属性和实现INotifyPropertyChanged，并瞧，您的视图模型可以只通过设置属性关闭窗口（并设置其的DialogResult）。 MVVM理所应当的。
This is almost as clean as if the WPF team had gotten it right and made DialogResult a dependency property in the first place. Just put a bool? DialogResult property on your ViewModel and implement INotifyPropertyChanged, and voilà, your ViewModel can close the Window (and set its DialogResult) just by setting a property. MVVM as it should be.
这里的code为DialogCloser：
Here's the code for DialogCloser:
using System.Windows;
namespace ExCastle.Wpf
{
public static class DialogCloser
{
public static readonly DependencyProperty DialogResultProperty =
DependencyProperty.RegisterAttached(
"DialogResult",
typeof(bool?),
typeof(DialogCloser),
new PropertyMetadata(DialogResultChanged));
private static void DialogResultChanged(
DependencyObject d,
DependencyPropertyChangedEventArgs e)
{
var window = d as Window;
if (window != null)
window.DialogResult = e.NewValue as bool?;
}
public static void SetDialogResult(Window target, bool? value)
{
target.SetValue(DialogResultProperty, value);
}
}
}
我也张贴了这个上我的博客。
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