DataGrid生成空行 [英] DataGrid generates empty rows

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本文介绍了DataGrid生成空行的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我有两个线程 - 我们将它们命名为Calc线程和UI线程。在Calc线程内，我刷新一个ObservableCollection。我也有一个ObservableCollection的CollectionChanged事件处理程序。正如我所知，处理程序在引发CollectionChanged事件的同一个线程中执行，所以这是在我的情况下刷新ObservableCollection的线程。所以，要刷新UI，我不能像单线程应用程序那样直接使用绑定 - 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：



数据网格左边的情况，右边的列表框案例



（列表框只是例如数据绑定和显示;我不希望显示数据像在这个列表框中，但像数据网格（如果它按照我的预期工作 - 不如图片中的情况） - 表的列标题）





嗯，我准备好了代码，您可以复制并粘贴以重建问题：



C＃

 使用System.Collections.ObjectModel; 
使用System.Collections.Specialized; 
使用System.Threading; 
使用System.Windows; 
 
命名空间WpfApplication1 
 {
 public class MyClass 
 {
 public int Integer {get;组; } 
 public string Str {get;组; } 
} 
 
 public partial class MainWindow：Window 
 {
 public ObservableCollection< MyClass> MyCollection {get;组; } 
 
 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（
对象发件人，
 NotifyCollectionChangedEventArgs e）
 {
 Dispatcher.Invoke（
（）= > 
 {
 foreach（e.NewItems中的var item）
 dataGrid.Items.Add（（MyClass）item）; 
}）; 
} 
} 
}

XAML（只是注释/取消注释列表框案例和数据网格案例）：

 < Window 
x： Class =WpfApplication1.MainWindow
 xmlns =http://schemas.microsoft.com/winfx/2006/xaml/presentation
 xmlns：x =http://schemas.microsoft.com / winfx / 2006 / xaml
 Title =MainWindowHeight =350Width =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>


解决方案

这是你想要的吗？



C＃

 命名空间WpfApplication1 
 {
 public class MyClass 
 {
 public int Integer {get;组; } 
 public string Str {get;组; } 
} 
 
 public partial class MainWindow：Window 
 {
 public ObservableCollection< MyClass> MyCollection {get;组; } 
 
 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 =MainWindowHeight =350Width = 525> 
 
< Grid> 
< DataGrid Name =dataGridItemsSource ={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列表：

  public partial class MainWindow：Window 
 {
 private List< MyClass> _我的收藏; 
 public ObservableCollection< MyClass> MyCollection {get;组; } 
 
 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]）; 
} 
} 
}

第二次编辑与你的例子： 

 命名空间WpfApplication1 
 {
 public class MyClass 
 {
 public int Integer {get;组; } 
 public string Str {get;组; } 
} 
 
 public partial class MainWindow：Window 
 {
 private ObservableCollection< MyClass> _我的收藏; 
 public ObservableCollection< MyClass> MyCollection {get;组; } 
 
 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（e.NewItems中的var item）
 MyCollection.Add（（MyClass）项）; 
}））; 
} 
} 
}


I have two threads - let's name them Calc thread and UI thread. Inside the Calc thread I refreshes an ObservableCollection. I also have a handler for the CollectionCHanged event of the ObservableCollection. As I know, the handler executes within the same thread that raises the CollectionChanged event - so that is the same thread that refreshes the ObservableCollection in my case. So, to refresh UI I can't use bindings directly as in single-threaded application - UI must be refreshed manually through Dispatcher. But when I use DataGrid in the UI I get the empty rows instead of any data, and when I use ListBox, for example, the appropriate data is showed:

data grid case to the left, list box case to the right

(list box is just for example that the data binds and shows; I don't want the data to be showed like in this list box, but like in data grid (if it worked as I expect - not as in case on the picture) - table with column titles)

Well, I prepared the code, which you can copy and paste to reconstruct the problem:

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 (just comment/uncomment the list box case and the data grid case):

<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>

解决方案

Is this what you want?

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>

Other method is to use another 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]);
            }
        }
    }

Second edit with you example:

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);
                }));
        }
    }
}

这篇关于DataGrid生成空行的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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