如何解决WPF MVVM 绑定命令到 Datagrid
我正在创建一个包含 2 个窗口的 WPF 模具应用程序：带有 DataGrid 的 MainWindow 和允许添加/编辑模具的 AddEditWindow。
我有一个位于 DataGrid 的 TemplateColumn 中的 EditButton：
<DataGridTemplateColumn Width="Auto">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<Button Width="150"
Height="40"
BorderThickness="2"
BorderBrush="DarkRed"
Background="Red"
Foreground="White"
Content="Edit"
Name="BtnEdit"
CommandParameter="{Binding}"
Command="{Binding RelativeSource={RelativeSource AncestorType={x:Type Window}},Path=DataContext.AddEditWindowCommand}">
</Button>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
添加编辑窗口命令：
public ICommand AddEditWindowCommand { get; }
private bool CanAddEditWindowCommandExecute(object SelectedRow) => true;
private void OnAddEditWindowCommandExecuted(object SelectedRow)
{
AddEditWindow window = new AddEditWindow();
window.Show();
}
我想将 DataContext 传递给 AddEditWindowViewModel。在代码隐藏中，我可以做这样的事情：
private void BtnEdit_Click(object sender,RoutedEventArgs e)
{
AddEditWindow addEditWindow = new AddEditWindow((sender as Button).DataContext as Molds);
addEditWindow.Show();
}
然后像这样检索它AddEditWindow：
private Molds _currentMold = new Molds();
public GamesEdit(Molds selectedMold)
{
InitializeComponent();
if (selectedMold != null)
{
_currentMold = selectedMold;
}
DataContext = _currentMold;
但在 MVVM 中我不能。那么，有没有办法在不破坏 MVVM 模式的情况下做到这一点？
附言由于我是 MVVM 的新手，我非常感谢详细的解释。
更新：
主窗口视图模型：
internal class MainWindowViewModel : ViewModel
{
#region Variables
#region Textblocks for search
private Molds newMolds { get; set; } = new Molds();
public string TxtType
{
get => newMolds.Type;
set => newMolds.Type = value;
}
public string TxtName
{
get => newMolds.Name;
set => newMolds.Name = value;
}
public string TxtKus
{
get => newMolds.Kus;
set => newMolds.Kus = value;
}
#endregion
#region AllMolds
private ObservableCollection<Molds> allMolds = new ObservableCollection<Molds>(ApplicationContext.GetContext().Molds.ToList());
public ObservableCollection<Molds> AllMolds
{
get => allMolds;
set => allMolds = value;
}
#endregion
#region FilteredMolds
private ObservableCollection<Molds> filteredMolds = new ObservableCollection<Molds>(ApplicationContext.GetContext().Molds.ToList());
public ObservableCollection<Molds> FilteredMolds
{
get
{
filteredMolds = AllMolds;
var currentfilteredmolds = new List<Molds>(filteredMolds);
if (TxtName != null)
currentfilteredmolds = currentfilteredmolds.Where(p => p.Name.ToLower().Contains(TxtName.ToLower())).ToList();
if (TxtType != null)
currentfilteredmolds = currentfilteredmolds.Where(p => p.Type.ToLower().Contains(TxtType.ToLower())).ToList();
if (TxtKus != null)
currentfilteredmolds = currentfilteredmolds.Where(p => p.Kus.ToLower().Contains(TxtKus.ToLower())).ToList();
return new ObservableCollection<Molds>(currentfilteredmolds);
}
set => filteredMolds = value;
}
#endregion
#endregion
#region Commands
#region CloseApplicationCommand
public ICommand CloseApplicationCommand { get; }
private bool CanCloseApplicationCommandExecute(object p) => true;
private void OnCloseApplicationCommandExecuted(object p)
{
Application.Current.Shutdown();
}
#endregion
#region SearchCommand
public ICommand SearchCommand { get; }
private bool CanSearchCommandExecute(object p) => true;
private void OnSearchCommandExecuted(object p)
{
OnPropertyChanged("FilteredMolds");
}
#endregion
#region Open AddEditWindowCommand
public ICommand AddEditWindowCommand { get; }
private bool CanAddEditWindowCommandExecute(object SelectedRow) => true;
private void OnAddEditWindowCommandExecuted(object SelectedRow)
{
AddEditWindow window = new AddEditWindow();
window.Show();
}
#endregion
#region DeleteMoldCommand
public ICommand DeleteMoldCommand { get; }
private bool CanDeleteMoldCommandExecute(object SelectedItems)
{
if (SelectedItems != null) return true; else return false;
}
private void OnDeleteMoldCommandExecuted(object SelectedItems)
{
System.Collections.IList items = (System.Collections.IList)SelectedItems;
var moldsforRemoving = items?.Cast<Molds>().ToList();
if (MessageBox.Show($"You want to remove the following {moldsforRemoving.Count()} molds?","Attention",MessageBoxButton.YesNo,MessageBoxImage.Question) == MessageBoxResult.Yes)
{
try
{
ApplicationContext.GetContext().Molds.RemoveRange(moldsforRemoving);
ApplicationContext.GetContext().SaveChanges();
MessageBox.Show("Data deleted successfully.","Data deletion",MessageBoxButton.OK,MessageBoxImage.Information);
AllMolds = new ObservableCollection<Molds>(ApplicationContext.GetContext().Molds.ToList());
OnPropertyChanged("FilteredMolds");
}
catch (Exception ex)
{
MessageBox.Show(ex.Message.ToString(),"Error",MessageBoxImage.Error);
}
}
}
#endregion
#region DragMoveCommand
public ICommand DragMoveCommand { get; }
private bool CanDragMoveCommandExecute(object p) => true;
private void OnDragMoveCommandExecuted(object p)
{
Application.Current.MainWindow.DragMove();
}
#endregion
#endregion
public MainWindowViewModel()
{
#region Command Samples
CloseApplicationCommand = new LamdaCommand(OnCloseApplicationCommandExecuted,CanCloseApplicationCommandExecute);
SearchCommand = new LamdaCommand(OnSearchCommandExecuted,CanSearchCommandExecute);
AddEditWindowCommand = new LamdaCommand(OnAddEditWindowCommandExecuted,CanAddEditWindowCommandExecute);
DeleteMoldCommand = new LamdaCommand(OnDeleteMoldCommandExecuted,CanDeleteMoldCommandExecute);
DragMoveCommand = new LamdaCommand(OnDragMoveCommandExecuted,CanDragMoveCommandExecute);
#endregion
#region Variable Samples for searching
TxtName = null;
TxtKus = null;
TxtType = null;
#endregion
}
}
AddEditWindowViewModel
internal class AddEditWindowViewModel : ViewModel
{
#region Variables
private Molds _currentMold = new Molds();
#endregion
#region Commands
#region CloseWindowCommand
public ICommand CloseWindowCommand { get; }
private bool CanCloseWindowCommandExecute(object p) => true;
private void OnCloseWindowCommandExecuted(object p)
{
Application.Current.Windows[1].Close();
}
#endregion
#region DragMoveAddEditWindowCommand
public ICommand DragMoveAddEditWindowCommand { get; }
private bool CanDragMoveAddEditWindowCommandExecute(object p) => true;
private void OnDragMoveAddEditWindowCommandExecuted(object p)
{
Application.Current.Windows[1].DragMove();
}
#endregion
#endregion
public AddEditWindowViewModel()
{
#region Command samples
CloseWindowCommand = new LamdaCommand(OnCloseWindowCommandExecuted,CanCloseWindowCommandExecute);
DragMoveAddEditWindowCommand = new LamdaCommand(OnDragMoveAddEditWindowCommandExecuted,CanDragMoveAddEditWindowCommandExecute);
#endregion
}
}
我使用
<Window.DataContext>
<vm:MainWindowViewModel/>
</Window.DataContext>
同样适用于 AddEditWindowViewModel。
DataGrid 绑定：
<DataGrid x:Name="DGridMolds"
AutoGenerateColumns="False"
IsReadOnly="True"
Foreground="White"
BorderBrush="White"
Background="#2b2a38"
Grid.Column="1"
Grid.Row="1"
ItemsSource="{Binding Path=FilteredMolds}"
>
AddEditWindow.Xaml：
<Window.DataContext>
<vm:AddEditWindowViewModel/>
</Window.DataContext>
<Border Background="#2f2e3c"
CornerRadius="10">
<Border.InputBindings>
<MouseBinding Command="{Binding DragMoveAddEditWindowCommand}" MouseAction="LeftClick"/>
</Border.InputBindings>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="30"/>
<RowDefinition/>
<RowDefinition Height="30"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="30"/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition Width="30"/>
</Grid.ColumnDefinitions>
<StackPanel Grid.Column="1" Grid.Row="1" Orientation="Vertical">
<TextBlock Text="Add" FontSize="22" Foreground="White" HorizontalAlignment="Center" Margin="0,30,0"/>
<TextBox Foreground="White" Text="{Binding Type,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Margin="5,35,5,5" materialDesign:HintAssist.Hint="Type"/>
<TextBox Foreground="White" Text="{Binding Name,UpdateSourceTrigger=PropertyChanged}" Margin="5" materialDesign:HintAssist.Hint="Name"/>
<TextBox Foreground="White" Text="{Binding Kus,UpdateSourceTrigger=PropertyChanged}" Margin="5" materialDesign:HintAssist.Hint="Kus"/>
解决方法
在代码隐藏中，我可以做这样的事情：
仔细查看您的 XAML。
您在 CommanParameter 属性中设置了绑定。
绑定实例为空 - 这意味着绑定发生在指定它的元素的 DataContext 上。
因此，在命令参数中，您将获得此数据上下文。
private void OnAddEditWindowCommandExecuted(object SelectedRow)
{
AddEditWindow window = new AddEditWindow()
{DataContext = SelectedRow};
window.Show();
}
那么，有没有办法在不破坏 MVVM 模式的情况下做到这一点？
你已经破坏了 MVVM。
不允许 ViewModel 与 UI 元素一起使用。
ViewModel 甚至不需要知道正在使用什么类型的 View：WPF、Forms 或 Console。
而你创造了窗户！
对于 MVVM 概念来说，这是不可接受的。
与在主要问题中显示更详细代码有关的补充：
我无法理解您代码的逻辑。 因此，我会在了解您的意图的情况下写下该措施。
AddEditWindowViewModel 类 - 设计用于编辑和/或添加项目的逻辑。 但随后他必须获取此元素并将其提供在他的属性中，以便他可以创建用于编辑的 GUI。
应该是这样的：
namespace MoldsApp
{
public class AddEditWindowViewModel : ViewModel
{
public Molds CurrentMold { get; }
// Constructor called to edit an entity
public AddEditWindowViewModel(Molds currentMold)
{
CurrentMold = currentMold;
}
//Constructor called to create and edit an entity
public AddEditWindowViewModel()
: this(new Molds())
{
}
}
}
此外，您的 DataContext 设置不正确。
通过在 XAML 中创建它，您无法为 ViewModel 的此实例设置数据。
因此，在 XAML 中，您可以实例化仅在其设计时使用的 ViewModel。
对于设计时 DataContext，请使用 d: 前缀。
<d:Window.DataContext>
<vm:MainWindowViewModel/>
</d:Window.DataContext>
有了这些变化，项目编辑命令应该是这样的：
private void OnAddEditWindowCommandExecuted(object SelectedRow)
{
AddEditWindow window = new AddEditWindow()
{
DataContext = new AddEditWindowViewModel((Molds)SelectedRow)
};
window.Show();
}
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