在带有MVVM的wpf中使用Dialog的好还是不好的做法？
我最近遇到了为wpf应用程序创建添加和编辑对话框的问题。
我想在代码中做的就是这样。（我主要在mvvm中使用viewmodel first方法）
调用对话框窗口的ViewModel：
var result = this.uiDialogService.ShowDialog("Dialogwindow Title", dialogwindowVM);// Do anything with the dialog result
它是如何工作的？
首先，我创建了一个对话框服务：
public interface IUIWindowDialogService{
bool? ShowDialog(string title, object datacontext);
}
public class WpfUIWindowDialogService : IUIWindowDialogService
{
public bool? ShowDialog(string title, object datacontext)
{
var win = new WindowDialog();
win.Title = title;
win.DataContext = datacontext;
return win.ShowDialog();
}
}
WindowDialog是一个特殊但简单的窗口。我需要它来保存我的内容：
<Window x:Class="WindowDialog" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
Title="WindowDialog"
WindowStyle="SingleBorderWindow"
WindowStartupLocation="CenterOwner" SizeToContent="WidthAndHeight">
<ContentPresenter x:Name="DialogPresenter" Content="{Binding .}">
</ContentPresenter>
</Window>
wpf中对话框的问题是dialogresult =
true只能在代码中实现。这就是为什么我创建了一个接口dialogviewmodel来实现它的原因。
public class RequestCloseDialogEventArgs : EventArgs{
public bool DialogResult { get; set; }
public RequestCloseDialogEventArgs(bool dialogresult)
{
this.DialogResult = dialogresult;
}
}
public interface IDialogResultVMHelper
{
event EventHandler<RequestCloseDialogEventArgs> RequestCloseDialog;
}
每当我的ViewModel认为是时候了dialogresult = true，请提出此事件。
public partial class DialogWindow : Window{
// Note: If the window is closed, it has no DialogResult
private bool _isClosed = false;
public DialogWindow()
{
InitializeComponent();
this.DialogPresenter.DataContextChanged += DialogPresenterDataContextChanged;
this.Closed += DialogWindowClosed;
}
void DialogWindowClosed(object sender, EventArgs e)
{
this._isClosed = true;
}
private void DialogPresenterDataContextChanged(object sender,
DependencyPropertyChangedEventArgs e)
{
var d = e.NewValue as IDialogResultVMHelper;
if (d == null)
return;
d.RequestCloseDialog += new EventHandler<RequestCloseDialogEventArgs>
(DialogResultTrueEvent).MakeWeak(
eh => d.RequestCloseDialog -= eh;);
}
private void DialogResultTrueEvent(object sender,
RequestCloseDialogEventArgs eventargs)
{
// Important: Do not set DialogResult for a closed window
// GC clears windows anyways and with MakeWeak it
// closes out with IDialogResultVMHelper
if(_isClosed) return;
this.DialogResult = eventargs.DialogResult;
}
}
现在至少我必须DataTemplate在资源文件（app.xaml或其他内容）中创建一个：
<DataTemplate DataType="{x:Type DialogViewModel:EditOrNewAuswahlItemVM}" > <DialogView:EditOrNewAuswahlItem/>
</DataTemplate>
好了，我现在可以从我的视图模型调用对话框：
var result = this.uiDialogService.ShowDialog("Dialogwindow Title", dialogwindowVM);现在我的问题是，您认为此解决方案有任何问题吗？
编辑：为了完整性。ViewModel应该实现IDialogResultVMHelper，然后可以在OkCommand或类似这样的范围内引发它：
public class MyViewmodel : IDialogResultVMHelper{
private readonly Lazy<DelegateCommand> _okCommand;
public MyViewmodel()
{
this._okCommand = new Lazy<DelegateCommand>(() =>
new DelegateCommand(() =>
InvokeRequestCloseDialog(
new RequestCloseDialogEventArgs(true)), () =>
YourConditionsGoesHere = true));
}
public ICommand OkCommand
{
get { return this._okCommand.Value; }
}
public event EventHandler<RequestCloseDialogEventArgs> RequestCloseDialog;
private void InvokeRequestCloseDialog(RequestCloseDialogEventArgs e)
{
var handler = RequestCloseDialog;
if (handler != null)
handler(this, e);
}
}
编辑2：我使用此处的代码使EventHandler的注册功能变弱：
http
:
//diditwith.net/2007/03/23/SolvingTheProblemWithEventsWeakEventHandlers.aspx
（网站不再存在，WebArchive
Mirror）
public delegate void UnregisterCallback<TE>(EventHandler<TE> eventHandler) where TE : EventArgs;
public interface IWeakEventHandler<TE>
where TE : EventArgs
{
EventHandler<TE> Handler { get; }
}
public class WeakEventHandler<T, TE> : IWeakEventHandler<TE>
where T : class
where TE : EventArgs
{
private delegate void OpenEventHandler(T @this, object sender, TE e);
private readonly WeakReference mTargetRef;
private readonly OpenEventHandler mOpenHandler;
private readonly EventHandler<TE> mHandler;
private UnregisterCallback<TE> mUnregister;
public WeakEventHandler(EventHandler<TE> eventHandler,
UnregisterCallback<TE> unregister)
{
mTargetRef = new WeakReference(eventHandler.Target);
mOpenHandler = (OpenEventHandler)Delegate.CreateDelegate(
typeof(OpenEventHandler),null, eventHandler.Method);
mHandler = Invoke;
mUnregister = unregister;
}
public void Invoke(object sender, TE e)
{
T target = (T)mTargetRef.Target;
if (target != null)
mOpenHandler.Invoke(target, sender, e);
else if (mUnregister != null)
{
mUnregister(mHandler);
mUnregister = null;
}
}
public EventHandler<TE> Handler
{
get { return mHandler; }
}
public static implicit operator EventHandler<TE>(WeakEventHandler<T, TE> weh)
{
return weh.mHandler;
}
}
public static class EventHandlerUtils
{
public static EventHandler<TE> MakeWeak<TE>(this EventHandler<TE> eventHandler,
UnregisterCallback<TE> unregister)
where TE : EventArgs
{
if (eventHandler == null)
throw new ArgumentNullException("eventHandler");
if (eventHandler.Method.IsStatic || eventHandler.Target == null)
throw new ArgumentException("Only instance methods are supported.",
"eventHandler");
var wehType = typeof(WeakEventHandler<,>).MakeGenericType(
eventHandler.Method.DeclaringType, typeof(TE));
var wehConstructor = wehType.GetConstructor(new Type[]
{
typeof(EventHandler<TE>), typeof(UnregisterCallback<TE>)
});
IWeakEventHandler<TE> weh = (IWeakEventHandler<TE>)wehConstructor.Invoke(
new object[] { eventHandler, unregister });
return weh.Handler;
}
}
回答：
这是一个好方法，我过去也使用过类似的方法。去吧！
我绝对要做的一件事是，当您需要在DialogResult中设置“ false”时，使事件接收一个布尔值。
event EventHandler<RequestCloseEventArgs> RequestCloseDialog;和EventArgs类：
public class RequestCloseEventArgs : EventArgs{
public RequestCloseEventArgs(bool dialogResult)
{
this.DialogResult = dialogResult;
}
public bool DialogResult { get; private set; }
}
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