Question

try
{
    sqlTran = conn.BeginTransaction();
    String tblAuto = "Select * from tblAuto_Num where Company_Code='Comp'AND Module='WSS' AND Sub_Module='SVS' AND Doc_Type='ORD'; ";
    SqlCommand cmd = new SqlCommand(tblAuto, conn);
    SqlDataReader reader = cmd.ExecuteReader();

    while (reader.Read())
    {  
    }           

    reader.Close();
    Label1.Text = "ttt";
    sqlTran.Commit();

    conn.Close();
}
catch (Exception ex)
{
    if (sqlTran != null) sqlTran.Rollback();
    Label1.Text = ex.toString();
}

我实施SqlDataReader reader = cmd.ExecuteReader();的那一刻，它会转到catch块。任何人都可以解释原因吗？

这是错误消息：

System.InvalidOperationException: ExecuteReader requires the command to have a transaction when the connection assigned to the command is in a pending local transaction. The Transaction property of the command has not been initialized. 
at System.Data.SqlClient.SqlCommand.ValidateCommand(String method, Boolean async) 
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean asyncWrite) 
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method) at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method) 
at System.Data.SqlClient.SqlCommand.ExecuteReader() at TicketApp.Default.ButtonAppointment_Click(Object sender, EventArgs e) 
in c:\Users\Farhad\Documents\Visual Studio 2013\Projects\TicketApp\TicketApp\Default.aspx.cs:line 29

Answer 1

在使用IDisposable时，使用使用代替 try..catch ：

using (var sqlTran = conn.BeginTransaction()) {
  // Format out SQL to be more readable
  String tblAuto = 
    @"select * 
        from tblAuto_Num 
       where Company_Code = 'Comp' and 
             Module = 'WSS' and 
             Sub_Module = 'SVS' and 
             Doc_Type='ORD'; ";

  try {
    using (SqlCommand cmd = new SqlCommand(tblAuto, conn)) {
      cmd.Transaction = sqlTran; // <- Do not forget this

      using (SqlDataReader reader = cmd.ExecuteReader()) {
        while (reader.Read()) {
          ...
        }
      } 
    }

    sqlTran.Commit();
  }
  catch (Exception) {
    try {
      sqlTran.Rollback();
      Label1.Text = "bbb";

      throw; // <- When catch Exception (base class)  do not forget to throw
    } 
    catch (Exception) {
      // when rollback can't be performed
      throw;
    }
  }
}

实施'读者'去阻止

1 个答案: