已经有与此连接关联的DataReader的开放必须先关闭VB.NET

Question

我收到此错误信息

“已经有与此连接 相关联的打开的DataReader，必须先关闭”

请帮我
我的代码是：

Public Sub update_qty(ByVal qry1 As String) 
     Dim dr As MySqlDataReader 'SQLiteDataReader 
     Dim comm As MySqlCommand 'SQLiteCommand 


     Try 

      comm = New MySqlCommand(qry1, conn) 
      dr = comm.ExecuteReader() 
     Catch ex As Exception 
      MsgBox(ex.Message) 
     End Try 

     Do While dr.Read() 
      exe_query("call cargosys.paymentsAdd('" & var1 & "', " & dr("inNo") & ")") 
     Loop 

     dr.Close() 
End Sub 

Public Sub exe_query(ByVal qry As String) As String 

     Dim cmd As MySqlCommand 

     Try 
      cmd = New MySqlCommand(qry, conn) 
      cmd.ExecuteNonQuery() 


     Catch ex As MySqlException 
      MessageBox.Show(ex.ToString)  
     End Try 

End Sub 

Answer 1

你的问题是，你的代码打开DataReader，然后执行SqlCommand当DataReader读

试图改变这一行：

dr = comm.ExecuteReader() 

到：

dr = comm.ExecuteReader(CommandBehavior.CloseConnection) 

更多：DataReader CommandBehavior

或更改您的连接字符串enabl e MARS（多活动结果集）。 此设置将允许在同一连接上检索多个只进，只读结果集。

例如：

connectionString= 
"Data Source=.\SQLEXPRESS; 
AttachDbFilename=|DataDirectory|Northwind.MDF; 
Integrated Security=True; 
User Instance=True; 
MultipleActiveResultSets=True" 

更多：MARS

编辑

由于MARS关键字不被支持，尝试你的代码改成这样：

Public Sub update_qty(ByVal qry1 As String) 
     Dim dr As MySqlDataReader 'SQLiteDataReader 
     Dim comm As MySqlCommand 'SQLiteCommand 


     Try 

      comm = New MySqlCommand(qry1, conn) 
      dr = comm.ExecuteReader() 
     Catch ex As Exception 
      MsgBox(ex.Message) 
     End Try 

     Dim myList As New List(Of String) 

     Do While dr.Read() 
      myList.Add("call cargosys.paymentsAdd('" & var1 & "', " & dr("inNo") & ")") 
     Loop 

     dr.Close() 
End Sub 

Public Sub exe_query(myList As List(Of String)) 

     Dim cmd As MySqlCommand 

     For Each query As String In myList 
      Try 
       cmd = New MySqlCommand(query, conn) 
       cmd.ExecuteNonQuery() 

      Catch ex As MySqlException 
       MessageBox.Show(ex.ToString)  
      End Try 
     Next 

End Sub 

而不是做DataReader.Read - >SqlCommand.ExecuteNonQuery同时，此代码将首先读取所有数据，然后运行SqlCommand.ExecuteNonQuery。