WPF DataGrid SelectedItem

3 回答

• 0

  运行以下示例，您将看到它为什么不起作用 .

  XAML：

  <Window x:Class="DataGridTest.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">
      <DockPanel>
          <TextBlock DockPanel.Dock="Bottom" Text="{Binding SelectedItem, ElementName=dataGrid}"/>
          <TextBlock DockPanel.Dock="Bottom" Text="{Binding SelectedItem}"/>
          <DataGrid x:Name="dataGrid" ItemsSource="{Binding Items}" SelectedItem="{Binding SelectedItem}" CanUserAddRows="True" CanUserDeleteRows="True" AutoGenerateColumns="False">
              <DataGrid.Columns>
                  <DataGridTextColumn Header="First Name" Binding="{Binding FirstName}"/>
                  <DataGridTextColumn Header="Last Name" Binding="{Binding FirstName}"/>
              </DataGrid.Columns>
          </DataGrid>
      </DockPanel>
  </Window>
  

  代码隐藏：

  namespace DataGridTest
  {
      using System.Collections.Generic;
      using System.Collections.ObjectModel;
      using System.ComponentModel;
      using System.Windows;
  
      public partial class MainWindow : Window, INotifyPropertyChanged
      {
          private readonly ICollection<Person> items;
          private Person selectedItem;
  
          public MainWindow()
          {
              InitializeComponent();
  
              this.items = new ObservableCollection<Person>();
              this.items.Add(new Person
                  {
                      FirstName = "Kent",
                      LastName = "Boogaart"
                  });
              this.items.Add(new Person
              {
                  FirstName = "Tempany",
                  LastName = "Boogaart"
              });
  
              this.DataContext = this;
          }
  
          public ICollection<Person> Items
          {
              get { return this.items; }
          }
  
          public Person SelectedItem
          {
              get { return this.selectedItem; }
              set
              {
                  this.selectedItem = value;
                  this.OnPropertyChanged("SelectedItem");
              }
          }
  
          private void OnPropertyChanged(string propertyName)
          {
              var handler = this.PropertyChanged;
  
              if (handler != null)
              {
                  handler(this, new PropertyChangedEventArgs(propertyName));
              }
          }
  
          public event PropertyChangedEventHandler PropertyChanged;
      }
  
      public class Person
      {
          public string FirstName
          {
              get;
              set;
          }
  
          public string LastName
          {
              get;
              set;
          }
  
          public override string ToString()
          {
              return FirstName + " " + LastName;
          }
      }
  }
  

  正如您在运行时所看到的那样，选择"new"行会导致将标记值设置为 DataGrid 中的所选项 . 但是，WPF无法将该sentinel项转换为 Person ，因此 SelectedItem 绑定无法转换 .

  要解决此问题，您可以在绑定上放置一个检测到标记的转换器，并在检测到时返回 null . 这是一个转换器，它这样做：

  namespace DataGridTest
  {
      using System;
      using System.Windows.Data;
  
      public sealed class SentinelConverter : IValueConverter
      {
          public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
          {
              return value;
          }
  
          public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
          {
              if (value != null && string.Equals("{NewItemPlaceholder}", value.ToString(), StringComparison.Ordinal))
              {
                  return null;
              }
  
              return value;
          }
      }
  }
  

  正如您所看到的，测试哨兵的 ToString() 值是一个不幸的必要，因为它是一种内部类型 . 您也可以（或另外）检查 GetType().Name 是 NamedObject .

  回复于 2024-04-29T06:48:35+08:00
• 0

  没有代码很难说，但我会看下面的内容 .

  确保每当删除一个项目并且它也是所选项目时，将ViewModel中绑定到property的选定项目设置为null . 您需要确保绑定到属性的SelectedItem不会被绑定 .

  回复于 2024-04-29T06:48:35+08:00
• 11

  听起来你忘了设置绑定模式，默认设置为OneWay . 这意味着您的视图中所做的任何更改都不会传播回您的视图模型 .

  并始终确保您拥有正确的datacontext .

  希望有所帮助 .

  回复于 2024-04-29T06:48:35+08:00