Linq to Sql 结果导致组合框异步

Question

我正在开发一个 winform 应用程序，并将在数据库中发出请求并异步填充我的组合框，但遇到访问控制问题，因为它们来自另一个线程，这是代码。

   this.backWorker.DoWork + = delegate
             {
                 comboBoxUsers.DataSource = repositoryUser.SelectAll();
                 comboBoxUsers.ValueMember = "UserId";
                 comboBoxUsers.DisplayMember = "Name";
             };

             backWorker.RunWorkerAsync ();

我正在研究 envoke 但我在实现它时遇到了困难， 我需要做的就是让 DoWork 事件可见进度条并选择执行此操作。

Answer 1

仅在BackgroundWorker上查询您的存储库并通过ProgressChangedEvenHandler将结果返回到UI

   //Set the ComboBox Properties on the Form, not in the worker.
   comboBoxUsers.ValueMember = "UserId";
   comboBoxUsers.DisplayMember = "Name";

   BackgroundWorker = new BackgroundWorker();
   worker.DoWork += Worker_DoWork;
   worker.WorkerReportsProgress = true;
   worker.ProgressChanged += new ProgressChangedEventHandler(Worker_ProgressChanged);

   private void Worker_DoWork(object sender, DoWorkEventArgs e)
   {
        BackgrounderWorker worker = (BackgroundWorker)sender;

        //Query the database
        //Instantiate a custom-class to contain the results
        IList<Users> users = userRepository.SelectAll();
        QueryResults results = new QueryResults(users);
        worker.ReportProgress(0, results);
   }

   //Back In the UI Layer
   private void Worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
   {
       var result = (QueryResult)e.UserState;
       comboBoxUsers.DataSource = result.Users;
   }

Answer 2

你的委托应该这样写：

this.backWorker.DoWork += delegate(object s, DoWorkEventArgs args)
{
  //...
}

有关如何从另一个线程访问 UI 线程的 UI 控件的详细信息，请参阅此处：

从Backgroundworker DoWork访问窗口控制

该链接有一个明确的答案，这里有一个片段：

this.Invoke(new MethodInvoker(delegate {

  // This code executes on the GUI thread.

}));