我一直在寻找我的问题的答案，但到目前为止没有运气。 我是MVVM的新手，但我正在利用一个可以投入使用的应用程序。
导航由绑定到对CommandParameter作出反应的RelayCommand / Action的Menu-Command实现。这将切换MainWindowViewModel中的CurrentViewModel。 MainWindow有一个ContentControl，其内容绑定到CurrentViewModel。以这种方式调用的视图都是通过DataTemplate实例化的UserControl。
<DataTemplate x:Shared="False" DataType="{x:Type vm:NewViewModel}">
<local:NewView/>
</DataTemplate>
当菜单调出视图时，它可以正常工作。再次单击相同的菜单会创建视图模型的新实例，但视图不会更改（旧值仍然存在）。 没有太多关于此问题的帖子，因为它似乎取决于不通过将x：shared设置为false来共享视图实例。如上所述，这对我不起作用。我也试过setting the CurrentViewModel to null 在改变之前。
我可能错过了一个明显的解决方案。无论如何都会很乐意提供帮助。
以下是代码:(案例：“正确”无效）
private InvoiceViewModel _InvoiceViewModel = new InvoiceViewModel();
private ProductsViewModel _ProductsViewModel = new ProductsViewModel();
private PrintViewModel _PrintViewModel = new PrintViewModel();
private CorrectInvoiceViewModel _CorrectInvoiceViewModel = new CorrectInvoiceViewModel();
private RetouchInvoiceViewModel _RetouchInvoiceViewModel = new RetouchInvoiceViewModel();
private CorrectionChainViewModel _CorrectionChainViewModel = new CorrectionChainViewModel();
private RecipientsViewModel _RecipientsViewModel = new RecipientsViewModel();
private AdjustmentsViewModel _AdjustmentsViewModel = new AdjustmentsViewModel();
private ViewModelBase _CurrentViewModel;
public ViewModelBase CurrentViewModel { get { return _CurrentViewModel; } set { SetProperty(ref _CurrentViewModel, value);} }
private void OnMenuItemClick(string destination)
{
switch (destination)
{
case "Invoice":
CurrentViewModel = _InvoiceViewModel;
ViewModelTitle = "Neue Rechnung";
break;
case "Products":
CurrentViewModel = _ProductsViewModel;
ViewModelTitle = "Produkte bearbeiten";
break;
case "Correct":
{
CurrentViewModel = null;
CurrentViewModel = new CorrectInvoiceViewModel();
ViewModelTitle = "Rechnungskorrektur";
break;
}
case "Retouch":
{
CurrentViewModel = _RetouchInvoiceViewModel;
ViewModelTitle = "Retusche";
break;
}
case "CorrectionChain":
{
CurrentViewModel = _CorrectionChainViewModel;
ViewModelTitle = "Rechnungsansicht und Korrekturreihe";
break;
}
case "Recipients":
{
CurrentViewModel = _RecipientsViewModel;
ViewModelTitle = "Empfänger bearbeiten";
break;
}
case "Adjustments":
{
CurrentViewModel = _AdjustmentsViewModel;
ViewModelTitle = "Adressfeld anpassen";
break;
}
default:
CurrentViewModel = null;
break;
}
}
和xaml：
<Controls:MetroWindow x:Name="wdw_Main" x:Class="PraxMat_View.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:PraxMat_View"
xmlns:Controls="clr-namespace:MahApps.Metro.Controls;assembly=MahApps.Metro"
xmlns:viewmod="clr-namespace:PraxMat_ViewModel;assembly=PraxMat_ViewModel"
DataContext="{StaticResource MainWindowViewModel_Resource}"
mc:Ignorable="d"
Title="PraxMat" Height="800" Width="1200" WindowTitleBrush="#FF2D2D30" TitleCaps="False" Icon="images/PraxMat_Logo.png" Background="Black" BorderBrush="{DynamicResource Grey04}" BorderThickness="1">
<Controls:MetroWindow.Resources>
<DataTemplate x:Shared="False" DataType="{x:Type viewmod:InvoiceViewModel}">
<local:InvoiceView/>
</DataTemplate>
<DataTemplate x:Shared="False" DataType="{x:Type viewmod:ProductsViewModel}">
<local:ProductsView/>
</DataTemplate>
<DataTemplate x:Shared="False" DataType="{x:Type viewmod:PrintViewModel}">
<local:PrintView/>
</DataTemplate>
<DataTemplate x:Shared="False" DataType="{x:Type viewmod:CorrectInvoiceViewModel}">
<local:CorrectInvoiceView/>
</DataTemplate>
<DataTemplate x:Shared="False" DataType="{x:Type viewmod:RetouchInvoiceViewModel}">
<local:RetouchInvoiceView/>
</DataTemplate>
<DataTemplate x:Shared="False" DataType="{x:Type viewmod:CorrectionChainViewModel}">
<local:CorrectionChainView DataContext="{StaticResource CorrectInvoiceViewModel_Resource}"/>
</DataTemplate>
<DataTemplate x:Shared="False" DataType="{x:Type viewmod:RecipientsViewModel}">
<local:RecipientsView/>
</DataTemplate>
<DataTemplate x:Shared="False" DataType="{x:Type viewmod:AdjustmentsViewModel}">
<local:AdjustmentsView/>
</DataTemplate>
</Controls:MetroWindow.Resources>
<Grid x:Name="grd_Main" Opacity="{Binding Opacity}">
<Menu x:Name="men_Main" VerticalAlignment="Top" Height="30" Background="#FF1E1E1E" BorderBrush="{DynamicResource Grey07}" BorderThickness="0,0,0,1">
<MenuItem Header="Menu" Background="{x:Null}" Foreground="{StaticResource Grey02}" Margin="26,3,0,0" Template="{DynamicResource DropShadowSubmenu}" Width="100" Padding="6,2,6,4">
<MenuItem x:Name="mui_Invoice" Header="Neue Rechnung" Background="#FF1E1E1E" Foreground="{StaticResource Grey02}" Template="{DynamicResource DropShadowSubmenu}" BorderThickness="0" Width="150" Height="25" Padding="5,0,0,0" Command="{Binding MenuItemClick}" CommandParameter="Invoice" Margin="0,2,0,0"/>
<MenuItem x:Name="mui_AlterInvoice" Header="Rechnung anpassen" Background="#FF1E1E1E" Foreground="{StaticResource Grey02}" Template="{DynamicResource DropShadowSubmenu_PopupRight}" BorderThickness="0" Width="150" Height="25" Padding="5,0,0,0">
<MenuItem.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel />
</ItemsPanelTemplate>
</MenuItem.ItemsPanel>
<MenuItem x:Name="mui_CorrectInvoice" Header="Korrektur" Background="#FF1E1E1E" Foreground="{StaticResource Grey02}" Template="{DynamicResource DropShadowSubmenu}" BorderThickness="0" Width="150" Height="25" Padding="0" Command="{Binding MenuItemClick}" CommandParameter="Correct" Margin="0,-4,0,0" />
<MenuItem x:Name="mui_RetouchInvoice" Header="Retusche" Background="#FF1E1E1E" Foreground="{StaticResource Grey02}" Template="{DynamicResource DropShadowSubmenu}" BorderThickness="0" Width="150" Height="25" Padding="0" Command="{Binding MenuItemClick}" CommandParameter="Retouch" />
<MenuItem x:Name="mui_CorrectionChain" Header="Ansicht/Korrekturreihe" Background="#FF1E1E1E" Foreground="{StaticResource Grey02}" Template="{DynamicResource DropShadowSubmenu}" BorderThickness="0" Width="150" Height="25" Padding="0" Command="{Binding MenuItemClick}" CommandParameter="CorrectionChain"/>
</MenuItem>
<MenuItem x:Name="mui_Payments" Header="Zahlungen" Background="#FF1E1E1E" Foreground="{StaticResource Grey02}" Template="{DynamicResource DropShadowSubmenu}" BorderThickness="0" Width="150" Height="25" Padding="5,0,0,0" Command="{Binding MenuItemClick}" CommandParameter="Payment"/>
<MenuItem Header="Diverses" Background="#FF1E1E1E" Foreground="{StaticResource Grey02}" Template="{DynamicResource DropShadowSubmenu_PopupRight}" BorderThickness="0" Width="150" Height="25" Padding="5,0,0,0">
<MenuItem.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel />
</ItemsPanelTemplate>
</MenuItem.ItemsPanel>
<MenuItem x:Name="mui_Products" Header="Produkte" Background="#FF1E1E1E" Foreground="{StaticResource Grey02}" Template="{DynamicResource DropShadowSubmenu}" BorderThickness="0" Width="150" Height="25" Padding="5,0,0,0" Command="{Binding MenuItemClick}" CommandParameter="Products" Margin="0,-4,0,0"/>
<MenuItem x:Name="mui_Recipients" Header="Empfänger" Background="#FF1E1E1E" Foreground="{StaticResource Grey02}" Template="{DynamicResource DropShadowSubmenu}" BorderThickness="0" Width="150" Height="25" Padding="5,0,0,0" Command="{Binding MenuItemClick}" CommandParameter="Recipients"/>
<MenuItem x:Name="mui_Adjustments" Header="Adressfeld" Background="#FF1E1E1E" Foreground="{StaticResource Grey02}" Template="{DynamicResource DropShadowSubmenu}" BorderThickness="0" Width="150" Height="25" Padding="5,0,0,0" Command="{Binding MenuItemClick}" CommandParameter="Adjustments"/>
</MenuItem>
</MenuItem>
<MenuItem Header="{Binding ViewModelTitle}" Margin="60,3,0,0 " Padding="6,2,6,4" Background="{x:Null}" Foreground="{StaticResource Grey02}" Template="{DynamicResource DropShadowSubmenu}" IsEnabled="False" ></MenuItem>
</Menu>
<ScrollViewer Margin="0,30,0,0" Background="{DynamicResource Grey09}" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
<ContentControl Content="{Binding CurrentViewModel}" Background="#FF06B836">
</ContentControl>
</ScrollViewer>
</Grid>
答案 0 :(得分：1)
等待确认，但在聊天一段时间后，看起来问题可能是CorrectInvoiceView.xaml中的这个问题
<UserControl.DataContext>
<StaticResource ResourceKey="CorrectInvoiceViewModel_Resource"/>
</UserControl.DataContext>
当DataTemplate更改为CorrectInvoiceViewModel时，CurrentViewModel CorrectInvoiceViewModel CurrentViewModel被正确实例化了。它使用DataContext的值|进行实例化，然后用其他东西替换该DataContext - 该视图模型的存储副本，始终是相同的存储副本，因为它被定义为某个地方的资源。
因此，如果您删除这三行，我认为您应该看到它按预期运行。