我试图进行异步调用以将数据加载到我的网格。问题是,操作阻塞了UI(在主线程中运行) - 我不知道为什么。我试图让它在后台取数据...下面的代码:Task.Run阻止主线程(冻结的UI)
绑定视图模型类的DataContext主窗口:
<Window.DataContext>
<vm:MainWindowViewModel WindowTitle="MVVM" BtnLoadText="LOAD DATA"/>
</Window.DataContext>
在DataGrid中列绑定到集合属性( PeopleList)在ViewModel类:在主窗口的
<DataGrid AutoGenerateColumns="False" IsReadOnly="True" ItemsSource="{Binding Path=PeopleList, Mode=TwoWay}" Margin="5">
<DataGrid.Columns>
<DataGridTextColumn Header="First name" Binding="{Binding Path=FirstName}"/>
<DataGridTextColumn Header="Last name" Binding="{Binding Path=LastName}"/>
<DataGridTextColumn Header="Age" Binding="{Binding Path=Age}"/>
</DataGrid.Columns>
</DataGrid>
<Button x:Name="btn_LoadData" Margin="5" Grid.Row="1" Content="{Binding Path=BtnLoadText}" Click="btn_LoadData_Click"/>
代码隐藏 - 异步运行按钮单击事件:
public partial class MainWindow : Window
{
private MainWindowViewModel mainWindowViewModel;
public MainWindow()
{
InitializeComponent();
mainWindowViewModel = (MainWindowViewModel)DataContext;
}
private async void btn_LoadData_Click(object sender, RoutedEventArgs e)
{
await mainWindowViewModel.LoadData();
}
}
ViewModel类负责主窗口:
class MainWindowViewModel
{
public string WindowTitle { get; set; }
public string BtnLoadText { get; set; }
public ObservableCollection<Person> PeopleList { get; set; }
private Database database = new Database();
public MainWindowViewModel()
{
PeopleList = new ObservableCollection<Person>();
}
public async Task LoadData()
{
PeopleList.Clear();
var result = await database.GetPeopleListLongOperationAsync();
PeopleList.Add(result.First());
}
}
正如你看到的,我正在做与LoadData方法,它从数据库中获取数据的异步调用并将其添加到的ObservableCollection,这将更新数据网格(从绑定数据网格)
数据库类,其中“模拟”的数据抓取:
public class Database
{
public IEnumerable<Person> GetPeopleListLongOperation()
{
// forcing "long" data load
Thread.Sleep(5000);
yield return new Person() { FirstName = "Name", LastName = "LastName", Age = new Random().Next(18, 40) };
}
public Task<IEnumerable<Person>> GetPeopleListLongOperationAsync()
{
return Task.Run<IEnumerable<Person>>(() =>
{
return GetPeopleListLongOperation();
});
}
}
我使用Task.Run获取在后台线程数据。问题是 - 它在Main Thread中运行,并且阻塞了UI。
有什么建议吗?我不知道了,如果我理解正确的异步操作...
编辑
自IEnumerable更改任务结果类型列出使其正常工作。有人可以解释我为什么吗?
public Task<List<Person>> GetPeopleListLongOperationAsync()
{
return Task.Run<List<Person>>(() =>
{
return GetPeopleListLongOperation().ToList();
});
}
谢谢。我知道关于IEnumerable集合的延迟加载,但我不知道它是这样工作的。 – asiesom