調用線程無法訪問此對象

Question

此代碼「var results ..」拋出異常「調用線程無法訪問此對象，因爲不同的線程擁有它」。 LINQ查詢不錯。

請問我做錯了什麼？

DataClassesDataContext db = new DataClassesDataContext(); 

    bool doStg() 
    { 
     try 
     { 
      var results = from t in db.table 
          select t; 

      //doing some things.. 

      return true; 
     } 
     catch (Exception Exception) 
     { 
      MessageBox.Show(Exception.Message); 
      return false; 
     } 
    } 

    bool stepByStep() 
    { 
     Dispatcher.BeginInvoke(new Action(() => info.Text = "Step 1"), null); 
     if (!doStg()) { return false; } 
     Dispatcher.BeginInvoke(new Action(() => progressBar.Value = 33), null); 

     Dispatcher.BeginInvoke(new Action(() => info.Text = "Step 2"), null); 
     if (!doStg()) { return false; } 
     Dispatcher.BeginInvoke(new Action(() => progressBar.Value = 66), null); 

     Dispatcher.BeginInvoke(new Action(() => info.Text = "Step 3"), null); 
     if (!doStg()) { return false; } 
     Dispatcher.BeginInvoke(new Action(() => progressBar.Value = 100), null); 

     return true; 
    } 

    private void button_Click(object sender, RoutedEventArgs e) 
    { 
     BackgroundWorker worker = new BackgroundWorker(); 

     worker.DoWork += delegate(object s, DoWorkEventArgs args) 
     { 
      args.Result = stepByStep(); 
     }; 

     worker.RunWorkerCompleted += delegate(object s, RunWorkerCompletedEventArgs args) 
     { 
      object result = args.Result; 
      if ((bool)result) { MessageBox.Show("Done"); } 
      else { MessageBox.Show("Processing stopped."); } 
     }; 

     worker.RunWorkerAsync(); 
    } 

編輯：

異常源： 「將System.Data.Linq」

TargetSite：{System.Data.Linq.SqlClient.SqlNode VisitInvocation（System.Linq.Expressions.InvocationExpression ）}

Answer 1

移動下面的代碼行：

DataClassesDataContext db = new DataClassesDataContext(); 

放入您的stepByStep()方法體中，然後將db作爲參數傳遞給您的doStg()方法。

bool doStg(DataClassesDataContext db) 
    { 
     try 
     { 
      var results = from t in db.table 
          select t; 

      //doing some things.. 

      return true; 
     } 
     catch (Exception Exception) 
     { 
      MessageBox.Show(Exception.Message); 
      return false; 
     } 
    } 

    bool stepByStep() 
    { 
     DataClassesDataContext db = new DataClassesDataContext(); 

     Dispatcher.BeginInvoke(new Action(() => info.Text = "Step 1"), null); 
     if (!doStg(db)) { return false; } 
     Dispatcher.BeginInvoke(new Action(() => progressBar.Value = 33), null); 

     Dispatcher.BeginInvoke(new Action(() => info.Text = "Step 2"), null); 
     if (!doStg(db)) { return false; } 
     Dispatcher.BeginInvoke(new Action(() => progressBar.Value = 66), null); 

     Dispatcher.BeginInvoke(new Action(() => info.Text = "Step 3"), null); 
     if (!doStg(db)) { return false; } 
     Dispatcher.BeginInvoke(new Action(() => progressBar.Value = 100), null); 

     return true; 
    }