Question

我正在使用WPF Toolkit的DataGrid。我在DataGrid上启用了属性以允许多行选择行。如何获取SelectedItems？我正在使用MVVM框架将我的ViewModel绑定到我的View。

谢谢！

Answer 1

考虑到Bill的答案，合并选项1和2，添加一些附加属性作为编写代码隐藏的替代方法，我想出了一个行为。

首先，我们有行为：

Public Class SelectedItemsBehavior

    Public Shared ReadOnly SelectedItemsChangedHandlerProperty As DependencyProperty =
        DependencyProperty.RegisterAttached("SelectedItemsChangedHandler",
            GetType(mvvm.RelayCommand), GetType(SelectedItemsBehavior),
            New FrameworkPropertyMetadata(New PropertyChangedCallback(AddressOf OnSelectedItemsChangedHandlerChanged)))




    Public Shared Function GetSelectedItemsChangedHandler(ByVal element As DependencyObject) As mvvm.RelayCommand
        If element Is Nothing Then Throw New ArgumentNullException("element")
        Return element.GetValue(SelectedItemsChangedHandlerProperty)
    End Function

    Public Shared Sub SetSelectedItemsChangedHandler(ByVal element As DependencyObject, ByVal value As mvvm.RelayCommand)
        If element Is Nothing Then Throw New ArgumentNullException("element")
        element.SetValue(SelectedItemsChangedHandlerProperty, value)
    End Sub

    Private Shared Sub OnSelectedItemsChangedHandlerChanged(d As DependencyObject,
                                                            e As DependencyPropertyChangedEventArgs)

        Dim dataGrid As DataGrid = DirectCast(d, DataGrid)

        If e.OldValue Is Nothing AndAlso e.NewValue IsNot Nothing Then
            AddHandler dataGrid.SelectionChanged, AddressOf ItemsControl_SelectionChanged
        End If

        If e.OldValue IsNot Nothing AndAlso e.NewValue Is Nothing Then
            RemoveHandler dataGrid.SelectionChanged, AddressOf ItemsControl_SelectionChanged
        End If

    End Sub


    Public Shared Sub ItemsControl_SelectionChanged(sender As Object,
                                                    e As SelectionChangedEventArgs)

        Dim dataGrid As DataGrid = DirectCast(sender, DataGrid)

        Dim itemsChangedHandler As RelayCommand = GetSelectedItemsChangedHandler(dataGrid)

        itemsChangedHandler.Execute(dataGrid.SelectedItems)

    End Sub

End Class

C＃：

using Microsoft.VisualBasic;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics;
public class SelectedItemsBehavior
{


    public static readonly DependencyProperty SelectedItemsChangedHandlerProperty = DependencyProperty.RegisterAttached("SelectedItemsChangedHandler", typeof(mvvm.RelayCommand), typeof(SelectedItemsBehavior), new FrameworkPropertyMetadata(new PropertyChangedCallback(OnSelectedItemsChangedHandlerChanged)));



    public static mvvm.RelayCommand GetSelectedItemsChangedHandler(DependencyObject element)
    {
        if (element == null)
            throw new ArgumentNullException("element");
        return element.GetValue(SelectedItemsChangedHandlerProperty);
    }

    public static void SetSelectedItemsChangedHandler(DependencyObject element, mvvm.RelayCommand value)
    {
        if (element == null)
            throw new ArgumentNullException("element");
        element.SetValue(SelectedItemsChangedHandlerProperty, value);
    }


    private static void OnSelectedItemsChangedHandlerChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        DataGrid dataGrid = (DataGrid)d;

        if (e.OldValue == null && e.NewValue != null) {
            dataGrid.SelectionChanged += ItemsControl_SelectionChanged;
        }

        if (e.OldValue != null && e.NewValue == null) {
            dataGrid.SelectionChanged -= ItemsControl_SelectionChanged;
        }

    }



    public static void ItemsControl_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        DataGrid dataGrid = (DataGrid)sender;

        RelayCommand itemsChangedHandler = GetSelectedItemsChangedHandler(dataGrid);

        itemsChangedHandler.Execute(dataGrid.SelectedItems);

    }

}

然后我们将它添加到XAML中的datagrid：

<DataGrid AutoGenerateColumns="False" FontFamily="Tahoma" FontSize="9"
          ItemsSource="{Binding Path=ResultsVM}" 
          mvvm:SelectedItemsBehavior.SelectedItemsChangedHandler="{Binding Path=ResultsSelectionChangedCommand}" />

然后我们在ViewModel中编写RelayCommand：

    Public ReadOnly Property ResultsSelectionChangedCommand() As mvvm.RelayCommand
        Get
            If _resultsSelectionChangedCommand Is Nothing Then
                _resultsSelectionChangedCommand = New mvvm.RelayCommand(AddressOf ResultsSelectionChanged)
            End If
            Return _resultsSelectionChangedCommand
        End Get
    End Property

    Public Sub ResultsSelectionChanged(ByVal selectedItems As Object)

        _resultsSelectedItems.Clear()
        For Each item In selectedItems
            _resultsSelectedItems.Add(item)
        Next

    End Sub

C＃：

public mvvm.RelayCommand ResultsSelectionChangedCommand {
    get {
        if (_resultsSelectionChangedCommand == null) {
            _resultsSelectionChangedCommand = new mvvm.RelayCommand(ResultsSelectionChanged);
        }
        return _resultsSelectionChangedCommand;
    }
}


public void ResultsSelectionChanged(object selectedItems)
{
    _resultsSelectedItems.Clear();
    foreach (item in selectedItems) {
        _resultsSelectedItems.Add(item);
    }

}

_resultsSelectedItems只是DataGrid中显示的项目列表：

    Private _resultsSelectedItems As New List(Of WorkOrderMatchViewModel)

C＃：

private List<WorkOrderMatchViewModel> _resultsSelectedItems = new List<WorkOrderMatchViewModel>();

希望这有帮助，有点使用Bill的方法而不必引用MVVM-Light。

Answer 2

我一直在寻找这个问题的答案。我找到的答案要么是

1）在代码隐藏委托中，将工作委托给ViewModel中的方法，从数据网格传递SelectedItems列表。此集合将包含所有选定的项目。

或

2）使用MVVM工具包灯，它允许您使用Event to Command并将对象作为参数直接传递给ViewModel。

private void DataGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    IList lst = this.myDataGrid.SelectedItems;
    ViewModel.RowsSelected(lst);
}

在这种情况下，您需要将xaml中的SelectionChanged绑定到后面代码中的selectionchanged。然后在您的代码隐藏中，您可以保存此列表并将其用于删除选定的行等。

如果有更好的方法可以做到这一点，我很乐意知道。

HTH

比尔

Answer 3

C＃版本SelectedItemsBehavior类。可能会帮助别人。

 public static class SelectedItemsBehavior
{
    public static readonly DependencyProperty SelectedItemsChangedHandlerProperty =
        DependencyProperty.RegisterAttached("SelectedItemsChangedHandler",
            typeof(RelayCommand),
            typeof(SelectedItemsBehavior),
            new FrameworkPropertyMetadata(new PropertyChangedCallback(OnSelectedItemsChangedHandlerChanged)));


    public static RelayCommand GetSelectedItemsChangedHandler(DependencyObject element)
    {
        if (element == null)
        {
            throw new ArgumentNullException("element");
        }
        return element.GetValue(SelectedItemsChangedHandlerProperty) as RelayCommand;
    }

    public static void SetSelectedItemsChangedHandler(DependencyObject element, RelayCommand value)
    {
        if (element == null)
        {
            throw new ArgumentNullException("element");
        }
        element.SetValue(SelectedItemsChangedHandlerProperty, value);
    }

    public static void OnSelectedItemsChangedHandlerChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {

        DataGrid dataGrid = (DataGrid)d;

        if (e.OldValue == null && e.NewValue != null)
        {
            dataGrid.SelectionChanged += new SelectionChangedEventHandler(ItemsControl_SelectionChanged);
        }

        if (e.OldValue != null && e.NewValue == null)
        {
            dataGrid.SelectionChanged -= new SelectionChangedEventHandler(ItemsControl_SelectionChanged);
        }
    }


    public static void ItemsControl_SelectionChanged(Object sender, SelectionChangedEventArgs e)
    {

        DataGrid dataGrid = (DataGrid)sender;

        RelayCommand itemsChangedHandler = GetSelectedItemsChangedHandler(dataGrid);

        itemsChangedHandler.Execute(dataGrid.SelectedItems);
    }
}

Answer 4

我设法用Bill提到的继电器命令来解决这个问题。部分内容有点脏，但我避免在后台文件中添加任何代码。

首先，在你的XAML中 - 将你的命令绑定到一个按钮，或任何触发你的RelayCommand。

<Button Content="Select" 
        cmd:ButtonBaseExtensions.Command="{Binding CommandSelect}"   
        cmd:ButtonBaseExtensions.CommandParameter="{Binding ElementName=Results, Path=SelectedItems}" />

您会注意到命令参数绑定到另一个UI元素 - 您希望获取所选项目的DataGrid或ListView。此语法在Silverlight 3和WPF中都有效，因为它现在支持元素到元素绑定。

在您的视图模型中，您的Command看起来像这样

Private _CommandSelect As RelayCommand(Of IEnumerable)

Public ReadOnly Property CommandSelect() As RelayCommand(Of IEnumerable)
    Get
        If _CommandSelect Is Nothing Then
            _CommandSelect = New RelayCommand(Of IEnumerable)(AddressOf CommandSelectExecuted, AddressOf CommandSelectCanExecute)
        End If
        Return _CommandSelect
    End Get
End Property


Private Function CommandSelectExecuted(ByVal parameter As IEnumerable) As Boolean

    For Each Item As IElectoralAreaNode In parameter

    Next

    Return True
End Function

Private Function CommandSelectCanExecute() As Boolean
    Return True
End Function

Selected Items将作为SelectedItemCollection返回，但您可能不希望View Model中具有此依赖性。所以输入它作为IEnumerable并进行一点点投射是你唯一的选择，那就是'肮脏'。但它保持你的代码清洁和MVVM模式！

WPF Toolkit DataGrid Multi-Select：如何获取SelectedItems？

4 个答案: