WPF中的MouseBinding手势未绑定到DataContext WPF

Question

I do not understand why my command is not properly executing when the user double clicks the listview item. I know for a fact the error occurs in the way it's binding. I'm not sure how to properly bind to the windows data context.

How can I bind to the windows data context from a nested control.

Here is the problematic code isolated...

<Grid.InputBindings>
    <MouseBinding Gesture="LeftDoubleClick" Command="{Binding EditCustomerCommand}"/>
</Grid.InputBindings>

MainWindow.xaml

<Window.DataContext>
        <viewModel:MainWindowViewModel />
    </Window.DataContext>

    <!--<Grid>
        <ContentPresenter Content="{Binding ActiveViewModel}"></ContentPresenter>
    </Grid>-->


    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>

        <Button Grid.Row="0" Content="Add New Person" Command="{Binding AddNewPersonCommand}"/>
        <ListView Grid.Row="1" ItemsSource="{Binding People}">
            <ListView.View>
                <GridView>
                    <GridViewColumn Header="First Name" Width="150">
                        <GridViewColumn.CellTemplate>
                            <DataTemplate>
                                <Grid Margin="0">
                                    <StackPanel Orientation="Horizontal">
                                        <Button Content="X" Width="20" 
                                                Command="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}, Path=DataContext.RemovePersonCommand}"
                                                CommandParameter="{Binding DataContext, RelativeSource={RelativeSource Self}}"
                                                />
                                        <Label  Content="{Binding FirstName}"/>
                                    </StackPanel>
                                    <Grid.InputBindings>
                                        <MouseBinding Gesture="LeftDoubleClick" Command="{Binding EditCustomerCommand}"/>
                                    </Grid.InputBindings>
                                </Grid>
                            </DataTemplate>
                        </GridViewColumn.CellTemplate>
                    </GridViewColumn>
                </GridView>
            </ListView.View>

            <ListView.Resources>
                <Style TargetType="{x:Type ListViewItem}">
                    <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"/>
                </Style>
            </ListView.Resources>

            <ListView.InputBindings>
                <KeyBinding Key="Delete" Command="{Binding DeleteCustomersCommand}"/>
            </ListView.InputBindings>

        </ListView>

        <StackPanel Grid.Row="2" Orientation="Horizontal">
            <Label Content="# People"/>
            <Label Content="{Binding PersonCount}"/>
        </StackPanel>

    </Grid>
</Window>

Answer 1

Please try the next solution, here I've used the freezable proxy class to get the access to the main view model. This case is similar to your problem, since the column can't access its parent data context directly.

Xaml code

<Window x:Class="DataGridSoHelpAttempt.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:dataGridSoHelpAttempt="clr-namespace:DataGridSoHelpAttempt"
    xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
    Title="MainWindow" Height="350" Width="525" x:Name="This">
<Window.DataContext>
    <dataGridSoHelpAttempt:MainViewModel/>
</Window.DataContext>
<Grid x:Name="MyGrid">
    <Grid.Resources>
        <dataGridSoHelpAttempt:FreezableProxyClass x:Key="ProxyElement" ProxiedDataContext="{Binding Source={x:Reference This}, Path=DataContext}"/>
    </Grid.Resources>
    <DataGrid x:Name="MyDataGrid" ItemsSource="{Binding DataSource}" AutoGenerateColumns="False">
        <DataGrid.Columns>
            <DataGridTextColumn Header="Name" Binding="{Binding Name}"/>
            <DataGridTextColumn Header="Description" Binding="{Binding Description}"  Visibility="{Binding Source={StaticResource ProxyElement}, 
                Path=ProxiedDataContext.Visibility, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
            <DataGridTextColumn Header="Comments" Binding="{Binding Comments}" Width="150"/>
            <DataGridTextColumn Header="Price (click to see total)" Binding="{Binding Price, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
        </DataGrid.Columns>
    </DataGrid>
    <StackPanel HorizontalAlignment="Stretch" VerticalAlignment="Bottom">
        <Button Content="Show Description" Command="{Binding Command}"></Button>
    </StackPanel>
</Grid>

View model and models

    public class MainViewModel:BaseObservableObject
{
    private Visibility _visibility;
    private ICommand _command;
    private Visibility _totalsVisibility;
    private double _totalValue;

    public MainViewModel()
    {
        Visibility = Visibility.Collapsed;
        TotalsVisibility = Visibility.Collapsed;
        DataSource = new ObservableCollection<BaseData>(new List<BaseData>
        {
            new BaseData {Name = "Uncle Vania", Description = "A.Chekhov, play", Comments = "worth reading", Price = 25},
            new BaseData {Name = "Anna Karenine", Description = "L.Tolstoy, roman", Comments = "worth reading", Price = 35},
            new BaseData {Name = "The Master and Margarita", Description = "M.Bulgakov, novel", Comments = "worth reading", Price = 56},
        });
    }

    public ICommand Command
    {
        get
        {
            return _command ?? (_command = new RelayCommand(VisibilityChangingCommand));
        }
    }

    private void VisibilityChangingCommand()
    {
        Visibility = Visibility == Visibility.Collapsed ? Visibility.Visible : Visibility.Collapsed;
    }

    public ObservableCollection<BaseData> DataSource { get; set; }

    public Visibility Visibility
    {
        get { return _visibility; }
        set
        {
            _visibility = value;
            OnPropertyChanged();
        }
    }

    public ObservableCollection<BaseData> ColumnCollection
    {
        get { return DataSource; }
    }

    public Visibility TotalsVisibility
    {
        get { return _totalsVisibility; }
        set
        {
            _totalsVisibility = value;
            OnPropertyChanged();
        }
    }

    public double TotalValue
    {
        get { return ColumnCollection.Sum(x => x.Price); }
    }

}

public class BaseData:BaseObservableObject
{
    private string _name;
    private string _description;
    private string _comments;
    private int _price;

    public virtual string Name
    {
        get { return _name; }
        set
        {
            _name = value;
            OnPropertyChanged();
        }
    }

    public virtual object Description
    {
        get { return _description; }
        set
        {
            _description = (string) value;
            OnPropertyChanged();
        }
    }

    public string Comments
    {
        get { return _comments; }
        set
        {
            _comments = value;
            OnPropertyChanged();
        }
    }

    public int Price
    {
        get { return _price; }
        set
        {
            _price = value;
            OnPropertyChanged();
        }
    }
}

Freezable proxy code

 public class FreezableProxyClass : Freezable
{
    protected override Freezable CreateInstanceCore()
    {
        return new FreezableProxyClass();
    }


    public static readonly DependencyProperty ProxiedDataContextProperty = DependencyProperty.Register(
        "ProxiedDataContext", typeof (object), typeof (FreezableProxyClass), new PropertyMetadata(default(object)));

    public object ProxiedDataContext
    {
        get { return (object) GetValue(ProxiedDataContextProperty); }
        set { SetValue(ProxiedDataContextProperty, value); }
    }
}

All is done due to the freezable object code, please take the solution as the starting point to your research. I'll glad to help if you will have problems with the code.

Regards. I'll glad to help you