如何获取 WPF DataGrid 的单元格级别 ComboBox？

Question

看来 WFP DataGridComboBoxColumn 对此列中的所有单元格使用单个 ItemsSource。我有一个情况，组合框项目依赖于同一行中的其他单元格。我设法在 PreparingCellForEdit 事件中填充 ItemsSource。但是，它并没有按预期工作。最初，该列中的所有单元格都是空的。一旦我填充此列的 ComboBox 的 ItemsSource，所有相关单元格（具有相同的项目源）都会显示值。但是，如果我单击另一种类型的单元格（填充不同的项目源），所有值都会消失，新类型的单元格会显示值。一列只能使用一组项目源？我不敢相信这是真的。我错过了什么吗？有什么解决办法吗？

Answer 1

你可能无法可靠地做到这一点。网格可以重用组合框或随机创建/销毁它。

一次偶然的机会，我正好在一个可以实现这一功能的屏幕上工作。鉴于这些...

• 网格中的每一行都绑定到 Trade 类型的对象。
• 每个 Trade 都有一个 State 属性
• 每个 Trade 都有一个 TerritoryCanidates 属性
• 更改 State 属性将导致 TerritoryCanidates 属性更改

这使我能够将 ItemsSource 绑定到 TerritoryCanidates 属性。 DataGrid 在所有情况下都会遵循这一点。

---

<Window x:Class="MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
    <DataGrid Name="Zoom" AutoGenerateColumns="False">
        <DataGrid.Columns>
            <DataGridTemplateColumn Header="State">
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate>
                        <TextBlock Text="{Binding State}" />
                    </DataTemplate>
                </DataGridTemplateColumn.CellTemplate>
                <DataGridTemplateColumn.CellEditingTemplate>
                    <DataTemplate>
                        <ComboBox SelectedItem="{Binding State}" ItemsSource="{Binding StateCanidates}" />
                    </DataTemplate>
                </DataGridTemplateColumn.CellEditingTemplate>
            </DataGridTemplateColumn>

            <DataGridTemplateColumn Header="Territory">
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate>
                        <TextBlock Text="{Binding Territory}" />
                    </DataTemplate>
                </DataGridTemplateColumn.CellTemplate>
                <DataGridTemplateColumn.CellEditingTemplate>
                    <DataTemplate>
                        <ComboBox SelectedItem="{Binding Territory}" ItemsSource="{Binding TerritoryCanidates}" />
                    </DataTemplate>
                </DataGridTemplateColumn.CellEditingTemplate>
            </DataGridTemplateColumn>

        </DataGrid.Columns>

    </DataGrid>
</Grid>
</Window>


Imports System.ComponentModel

Class MainWindow
Sub New()

    ' This call is required by the designer.
    InitializeComponent()

    ' Add any initialization after the InitializeComponent() call.
    Dim x As New List(Of Model)
    x.Add(New Model)
    x.Add(New Model)
    x.Add(New Model)

    Zoom.ItemsSource = x
End Sub
End Class

Class Model
Implements INotifyPropertyChanged

Public ReadOnly Property StateCanidates As List(Of String)
    Get
        Return New List(Of String) From {"CA", "TX", "NY"}
    End Get
End Property

Public ReadOnly Property TerritoryCanidates As List(Of String)
    Get
        If State = "" Then Return Nothing
        Return New List(Of String) From {State & "1", State & "2"}
    End Get
End Property

Private m_State As String
Public Property State() As String
    Get
        Return m_State
    End Get
    Set(ByVal value As String)
        m_State = value
        OnPropertyChanged("State")
        OnPropertyChanged("TerritoryCanidates")
    End Set
End Property

Private m_Territory As String
Public Property Territory() As String
    Get
        Return m_Territory
    End Get
    Set(ByVal value As String)
        m_Territory = value
        OnPropertyChanged("Territory")
    End Set
End Property




Public Sub OnPropertyChanged(ByVal propertyName As String)
    RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
End Sub

Public Event PropertyChanged(ByVal sender As Object, ByVal e As System.ComponentModel.PropertyChangedEventArgs) Implements System.ComponentModel.INotifyPropertyChanged.PropertyChanged
End Class

Answer 2

感谢乔纳森的例子，我解决了我的问题如下。我修改了 Jonathan 的代码以突出显示我的解决方案。我从他的示例中删除了 Territory 属性，因为我的问题不需要它。

有两列。第一列是状态。第二列是 StateCandidate。 State 列绑定到 States 列表，StateCandidate 列绑定到 StateCandidates 列表。关键点是，当 State 更改时，会重新创建 StateCandidates 列表。因此，每行中可能有不同的 StateCandidates 列表（基于所选的 State）。

MainWindow.xaml

<Window x:Class="WpfTest1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <DataGrid Name="Zoom" AutoGenerateColumns="False" Background="DarkGray" RowHeaderWidth="50" HeadersVisibility="All">
            <DataGrid.Columns>
                <DataGridTemplateColumn x:Name="colState" Header="State" Width="120">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <TextBlock Text="{Binding State}" />
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                    <DataGridTemplateColumn.CellEditingTemplate>
                        <DataTemplate>
                            <ComboBox SelectedItem="{Binding State}" ItemsSource="{Binding States}" />
                        </DataTemplate>
                    </DataGridTemplateColumn.CellEditingTemplate>
                </DataGridTemplateColumn>
                <DataGridTemplateColumn x:Name="colStateCandiate" Header="State Candidate" Width="200">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <TextBlock Text="{Binding StateCandidate}" />
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                    <DataGridTemplateColumn.CellEditingTemplate>
                        <DataTemplate>
                            <ComboBox SelectedItem="{Binding StateCandidate}" ItemsSource="{Binding StateCandidates}" />
                        </DataTemplate>
                    </DataGridTemplateColumn.CellEditingTemplate>
                </DataGridTemplateColumn>
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>

MainWindow.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.ComponentModel;

namespace WpfTest1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            List<Model> list = new List<Model>();
            list.Add(new Model() { State = "TX", StateCandidate = "TX2" });
            list.Add(new Model() { State = "CA" });
            list.Add(new Model() { State = "NY", StateCandidate = "NY1" });
            list.Add(new Model() { State = "TX" });
            list.Add(new Model() { State = "AK" });
            list.Add(new Model() { State = "MN" });

            Zoom.ItemsSource = list;
            Zoom.PreparingCellForEdit += new EventHandler<DataGridPreparingCellForEditEventArgs>(Zoom_PreparingCellForEdit);
        }

        void Zoom_PreparingCellForEdit(object sender, DataGridPreparingCellForEditEventArgs e)
        {
            if (e.Column == colStateCandiate)
            {                
                DataGridCell cell = e.Column.GetCellContent(e.Row).Parent as DataGridCell;
                cell.IsEnabled = (e.Row.Item as Model).StateCandidates != null;
            }
        }
    }
    public class Model : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        private string _state;
        private List<string> _states = new List<string>() { "CA", "TX", "NY", "IL", "MN", "AK" };
        private string _stateCandidate;
        private List<string> _stateCandidates;

        public string State
        {
            get { return _state; }
            set
            {
                if (_state != value)
                {
                    _state = value;
                    _stateCandidate = null;
                    if (_state == "CA" || _state == "TX" || _state == "NY")
                        _stateCandidates = new List<string> { _state + "1", _state + "2" };
                    else
                        _stateCandidates = null;
                    OnPropertyChanged("State");
                }
            }
        }
        public List<string> States
        {
            get { return _states; }
        }
        public string StateCandidate
        {
            get { return _stateCandidate; }
            set 
            {
                if (_stateCandidate != value)
                {
                    _stateCandidate = value;
                    OnPropertyChanged("StateCandidate");
                }
            }
        }
        public List<string> StateCandidates
        {
            get { return _stateCandidates; }
        }
        public void OnPropertyChanged(string name)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(name));
        }
    }
}

请注意，当状态更改时，它不会更新 StateCandidates 列表，直到选择不同的行，这是我将要解决的一个单独问题。有人知道我如何强制提交吗？

再次感谢乔纳森的灵感。我会继续寻找更好的解决方案。