DataGrid 生成空行

Question

我有两个线程 - 我们将它们命名为 Calc 线程和 UI 线程。在 Calc 线程中，我刷新了一个 ObservableCollection。我还有一个 ObservableCollection 的 CollectionCHanged 事件的处理程序。据我所知，处理程序在引发 CollectionChanged 事件的同一线程中执行 - 因此在我的情况下，这就是刷新 ObservableCollection 的同一线程。因此，要刷新 UI，我不能像在单线程应用程序中那样直接使用绑定 - UI 必须通过 Dispatcher 手动刷新。但是当我在 UI 中使用 DataGrid 时，我得到的是空行而不是任何数据，例如，当我使用 ListBox 时，会显示适当的数据：

左侧是数据网格大小写，右侧是列表框大小写

（列表框只是数据绑定和显示的示例；我不希望数据像在此列表框中那样显示，而是像在数据网格中那样显示（如果它按我预期的那样工作 - 不是以防万一在图片上）- 带有列标题的表格）

嗯，我准备了代码，你可以复制粘贴来重构问题：

C#

using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.Threading;
using System.Windows;

namespace WpfApplication1
{
    public class MyClass
    {
        public int Integer { get; set; }
        public string Str { get; set; }
    }    

    public partial class MainWindow : Window
    {
        public ObservableCollection<MyClass> MyCollection { get; set; }

        public MainWindow()
        {
            InitializeComponent();    

            MyCollection = new ObservableCollection<MyClass>();
            MyCollection.CollectionChanged += MyCollection_CollectionChanged;

            Thread t = new Thread(new ThreadStart(() =>
                {
                    for (int i = 0; i < 10; i++)
                    {
                        MyCollection.Add(new MyClass() 
                        {
                            Integer = i, 
                            Str = "String" + i
                        });
                        Thread.Sleep(500);
                    }
                }));

            t.Start();
        }

        void MyCollection_CollectionChanged(
            object sender, 
            NotifyCollectionChangedEventArgs e)
        {
            Dispatcher.Invoke(
                () =>
                {
                    foreach (var item in e.NewItems)
                        dataGrid.Items.Add((MyClass)item);
                });
        }
    }
}

XAML（只需注释/取消注释列表框大小写和数据网格大小写）：

<Window
  x:Class="WpfApplication1.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>

    <!--<ListBox Name="dataGrid">
      <ListBox.ItemTemplate>
        <DataTemplate>
          <StackPanel>
            <TextBlock Text="{Binding Path=Integer}" />
            <TextBlock Text="{Binding Path=Str}" />
          </StackPanel>
        </DataTemplate>
      </ListBox.ItemTemplate>
    </ListBox>-->

    <DataGrid Name="dataGrid">
      <DataGrid.ItemTemplate>
        <DataTemplate>
          <StackPanel>
            <TextBlock Text="{Binding Path=Integer}" />
            <TextBlock Text="{Binding Path=Str}" />
          </StackPanel>
        </DataTemplate>
      </DataGrid.ItemTemplate>
    </DataGrid>

  </Grid>
</Window>

Answer 1

这是你想要的吗？

C#

namespace WpfApplication1
{
    public class MyClass
    {
        public int Integer { get; set; }
        public string Str { get; set; }
    }

    public partial class MainWindow : Window
    {
        public ObservableCollection<MyClass> MyCollection { get; set; }

        public MainWindow()
        {
            InitializeComponent();
            DataContext = this;
            MyCollection = new ObservableCollection<MyClass>();

            Thread t = new Thread(new ThreadStart(() =>
            {
                for (int i = 0; i < 10; i++)
                {
                   Dispatcher.Invoke(new Action(() =>
                   {
                    MyCollection.Add(new MyClass()
                    {
                        Integer = i,
                        Str = "String " + i
                    });
                   }));
                }
            }));

            t.Start();
        }
    }
}

XAML

<Window
  x:Class="WpfApplication1.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="dataGrid" ItemsSource="{Binding MyCollection}">
            <DataGrid.ItemTemplate>
                <DataTemplate>
                    <StackPanel>
                        <TextBlock Text="{Binding Integer}" />
                        <TextBlock Text="{Binding Str}" />
                    </StackPanel>
                </DataTemplate>
            </DataGrid.ItemTemplate>
        </DataGrid>

    </Grid>
</Window>

其他方法是使用另一个List：

public partial class MainWindow : Window
    {
        private List<MyClass> _MyCollection;
        public ObservableCollection<MyClass> MyCollection { get; set; }

        private DispatcherTimer dispatcherTimer = new DispatcherTimer();

        public MainWindow()
        {
            InitializeComponent();
            DataContext = this;
            MyCollection = new ObservableCollection<MyClass>();
            _MyCollection = new List<MyClass>();
            dispatcherTimer.Interval = new TimeSpan(0, 0, 0, 0, 500);
            dispatcherTimer.Tick += new EventHandler(dispatcherTimer_Tick);

            Thread t = new Thread(new ThreadStart(() =>
            {
                for (int i = 0; i < 10; i++)
                {
                    _MyCollection.Add(new MyClass()
                    {
                        Integer = i,
                        Str = "String " + i
                    });
                    Thread.Sleep(500);
                }
            }));

            t.Start();
            dispatcherTimer.Start();
        }

        private void dispatcherTimer_Tick(object sender, EventArgs e)
        {
            if (_MyCollection.Count != MyCollection.Count)
            {
                MyCollection.Add(_MyCollection[_MyCollection.Count - 1]);
            }
        }
    }

与您一起进行第二次编辑示例：

namespace WpfApplication1
{
    public class MyClass
    {
        public int Integer { get; set; }
        public string Str { get; set; }
    }

    public partial class MainWindow : Window
    {
        private ObservableCollection<MyClass> _MyCollection;
        public ObservableCollection<MyClass> MyCollection { get; set; }

        public MainWindow()
        {
            InitializeComponent();
            DataContext = this;
            MyCollection = new ObservableCollection<MyClass>();
            _MyCollection = new ObservableCollection<MyClass>();
            _MyCollection.CollectionChanged += new NotifyCollectionChangedEventHandler(_MyCollection_CollectionChanged);

            Thread t = new Thread(new ThreadStart(() =>
            {
                for (int i = 0; i < 10; i++)
                {
                    _MyCollection.Add(new MyClass()
                    {
                        Integer = i,
                        Str = "String " + i
                    });
                    Thread.Sleep(500);
                }
            }));

            t.Start();
        }

        private void _MyCollection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            Dispatcher.Invoke(new Action(
                () =>
                {
                    foreach (var item in e.NewItems)
                        MyCollection.Add((MyClass)item);
                }));
        }
    }
}