在C＃winform中线程化以显示启动画面错误 [英] Threading in C# winform to show a splash screen ERROR

问题描述

大家好，

我试图显示启动画面，但显示以下错误：

 < b>跨线程操作无效：控制'cmbEnviroment'从其创建的线程以外的线程访问 

这是我的线程代码：

 private void LoadInstitutions（）
 { 
 //Thread.Sleep(3000）; 
 
 // OperationClass oc = new OperationClass（）; 
 // oc.loading（）; 
 string selectedValue = cmbEnviroment.SelectedItem.ToString（）。Trim（）; 
 ConnectionClass connectionClass = new ConnectionClass（）; 
 connectionClass.Connection（selectedValue）; 
 
 DataTable table4 = new DataTable（）; 
 
 string sql4 =收集数据的查询; 
 
 try 
 {
 
 OleDbDataAdapter da4 = new OleDbDataAdapter（sql4，connectionClass.Connection（selectedValue））; 
 da4.Fill（table4）; 
 DataRow dr4 = table4.NewRow（）; 
 DataRow dr5 = table4.NewRow（）; 
 dr4 [hello1] =; 
 table4.Rows.InsertAt（dr4,0）; 
 
 cmbInstitution.DataSource = table4; 
 cmbInstitution.DisplayMember =hello1; 
 cmbInstitution.ValueMember =hello1; 
} 
 catch（exception ex）
 {  
 MessageBox.Show（ex.ToString（））; 
} 
 
 
 
 
 
} 
 
 private async void cmbEnviroment_SelectedIndexChanged（object sender，EventArgs e）
 {
 
 //使用（new PleaseWait（this.Location））
 // {
 ComboBox senderComboBox =（ComboBox）sender; 
 if（senderComboBox.SelectedIndex> 0）
 {
 LoadingScreen ls = new LoadingScreen（）; 
 ls.TopMost = true; 
 ls.Show（）; 
 
 await Task.Run（（）=> LoadInstitutions（））; 
 
 ls.Close（）; 
} 
 //} 
 
} 
 

我尝试了什么：



我尝试了不同的方法来显示启动画面，而我正在从数据库收集数据但是我卡住了。

解决方案

你无法从UI线程以外的任何线程访问任何控件 - 当你尝试时，你会看到一个交叉线程异常。



解决此问题的两种方法：

1）调用控件而不是直接访问它： Control.Invoke方法（委托）（System.Windows.Forms） [ ^ ]

2）移动使用BackgroundWorker类将长时间运行的代码放入后台线程，后者旨在向UI线程提供进度信息以进行更新。

重构代码以将长时间运行的部分移动到后台线程，并保留在UI线程上访问UI的部分：

 私有 静态 DataTable LoadInstitutions（ string  selectedValue）
 {
 ConnectionClass connectionClass =  new  ConnectionClass（）; 
  const   string  sql =  收集数据的查询; 
 
 DataTable result =  new  DataTable（）; 
 OleDbDataAdapter da =  new  OleDbDataAdapter（sql，connectionClass.Connection（selectedValue））; 
 da.Fill（结果）; 
 
 DataRow dr = result.NewRow（）; 
 dr [  hello1] =   ; 
 result.Rows.InsertAt（dr， 0 ）; 
 
 返回结果; 
} 
 
  private   async 任务LoadInstitutions（）
 {
 尝试 
 {
  string  selectedValue = cmbEnviroment.SelectedItem的ToString（）修剪（）; 
 DataTable table =  await  Task.Run（（）= >  LoadInstitutions（selectedValue）） ; 
 cmbInstitution.DataSource = table4; 
 cmbInstitution.DisplayMember =   hello1; 
 cmbInstitution.ValueMember =   hello1; 
} 
  catch （Exception ex）
 {
 MessageBox.Show（ex.ToString（））; 
} 
} 
 
 私有  async   void  cmbEnviroment_SelectedIndexChanged（ object  sender，EventArgs e）
 {
 ComboBox senderComboBox =（ComboBox）发件人; 
  if （senderComboBox.SelectedIndex >   0 ）
 {
 LoadingScreen ls =  new  LoadingScreen（）; 
 ls.TopMost =  true ; 
 ls.Show（）; 
 尝试 
 {
  await  LoadInstitutions（）; 
} 
 最后 
 {
 ls.Close（）; 
} 
} 
} 

Hi guys ,
im trying to show splash screen but the following error is shown:

Cross-thread operation not valid: Control 'cmbEnviroment' accessed from a thread other than the thread it was created on

this is my code for the threading :

private void LoadInstitutions()
      {
          //Thread.Sleep(3000);

          // OperationClass oc = new OperationClass();
          // oc.loading();
          string selectedValue = cmbEnviroment.SelectedItem.ToString().Trim();
          ConnectionClass connectionClass = new ConnectionClass();
          connectionClass.Connection(selectedValue);

          DataTable table4 = new DataTable();

          string sql4 = "A query to gather data";

          try
          {

              OleDbDataAdapter da4 = new OleDbDataAdapter(sql4, connectionClass.Connection(selectedValue));
              da4.Fill(table4);
              DataRow dr4 = table4.NewRow();
              DataRow dr5 = table4.NewRow();
              dr4["hello1"] = "";
              table4.Rows.InsertAt(dr4, 0);

              cmbInstitution.DataSource = table4;
              cmbInstitution.DisplayMember = "hello1";
              cmbInstitution.ValueMember = "hello1";
          }
          catch (Exception ex)
          {
              MessageBox.Show(ex.ToString());
          }





      }

      private async void cmbEnviroment_SelectedIndexChanged(object sender, EventArgs e)
      {

          //using (new PleaseWait(this.Location))
          //{
              ComboBox senderComboBox = (ComboBox)sender;
              if (senderComboBox.SelectedIndex > 0)
              {
                  LoadingScreen ls = new LoadingScreen();
                  ls.TopMost = true;
                  ls.Show();

                  await Task.Run(() => LoadInstitutions());

                  ls.Close();
               }
          //}

      }

What I have tried:

im have tried different methods to show the splash screen while i'm gathering data from database but im stuck .

解决方案

You cannot access any control from any thread other than the UI thread - when you try, you get a "cross thread exception" as you are seeing.

Two ways to fix this:
1) Invoke the control instead of accessing it directly: Control.Invoke Method (Delegate) (System.Windows.Forms)[^]
2) Move your long running code into a background thread using the BackgroundWorker class which is designed to provide progress information to the UI thread for updates.

Refactor your code to move the long-running part to a background thread, and keep the parts that access the UI on the UI thread:

private static DataTable LoadInstitutions(string selectedValue)
{
    ConnectionClass connectionClass = new ConnectionClass();
    const string sql = "A query to gather data";
    
    DataTable result = new DataTable();
    OleDbDataAdapter da = new OleDbDataAdapter(sql, connectionClass.Connection(selectedValue));
    da.Fill(result);
    
    DataRow dr = result.NewRow();
    dr["hello1"] = "";
    result.Rows.InsertAt(dr, 0);
    
    return result;
}

private async Task LoadInstitutions()
{
    try
    {
        string selectedValue = cmbEnviroment.SelectedItem.ToString().Trim();
        DataTable table = await Task.Run(() => LoadInstitutions(selectedValue));
        cmbInstitution.DataSource = table4;
        cmbInstitution.DisplayMember = "hello1";
        cmbInstitution.ValueMember = "hello1";
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.ToString());
    }
}

private async void cmbEnviroment_SelectedIndexChanged(object sender, EventArgs e)
{
    ComboBox senderComboBox = (ComboBox)sender;
    if (senderComboBox.SelectedIndex > 0)
    {
        LoadingScreen ls = new LoadingScreen();
        ls.TopMost = true;
        ls.Show();
        try
        {
            await LoadInstitutions();
        }
        finally
        {
            ls.Close();
        }
    }
}

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