db.SaveChanges 在 ForEach 中导致 'New transaction is not allowed because there are other threads running in the session'

Question

我有一个 excel 文件，大约有 21000 行。我将它导入到我的数据库中的临时 Table。

现在我想对我的数据做一些转换，然后将它们放入我的主table。

当我在 foreach 中执行 SaveChanges() 时，出现以下错误：

Microsoft.Data.SqlClient.SqlException: 'New transaction is not allowed because there are other threads running in the session

当我在 foreach 之后使用它时，没有发生错误，并且 table 只插入了 4 条记录，而不是我预期的所有 21000 条记录。

     public ActionResult FeedTempdataToMainDB()
    {
        
        var L = new Leave();
        //  var leaves = new List<Leave>();
        foreach (var item in db.TempLeaves)
        {
            L.Pcode = Int32.Parse(item.Cod);
            var z = int.Parse(item.LT) - 1;
            if (z == 0) L.LT = Leave.LeaveType.Saati;
            else L.LT = Leave.LeaveType.Roozane;
            var o = int.Parse(item.DLT) - 1;
            if (o == 0) L.DLT = Leave.DLType.Estehghaghi;
            if (o == 1) L.DLT = Leave.DLType.Estelaji;
            else L.DLT = Leave.DLType.Bihoghoogh;
            L.LeaveDayStart = item.LeaveDayStart.Old6digToMiladi();
            L.LeaveDayEnd = item.LeaveDayEnd.Old6digToMiladi();
            L.LeaveTimeStart = StringToHour(item.LeaveTimeStart);
            L.LeaveTimeEnd = StringToHour(item.LeaveTimeEnd);
            L.LeaveDays = int.Parse(item.LeaveDays);
            L.LeaveMinuts = SaatiLengh(item.LeaveMinuts);
            L.RegDate = StringToHour(item.RegTime);
            L.RegDate = item.RegDate.Old6digToMiladi().Date;
            L.RegistrarCode = Int32.Parse(item.RegistrarCode);
            L.HijriYear = L.LeaveDayStart.GetHijriYear();
            var t = IsOk(item.RegTime);
            if (L.DLT == 0 && t == false || L.LT == 0)
            {
                L.Calculate = false;

                L.IsActive = false;
            }
            else { L.Calculate = true; L.IsActive = true; }
            db.Leaves.Add(L);
            db.SaveChangesAsync();
        }
        //db.SaveChanges();
        return RedirectToAction("index");

Answer 1

您的代码中有错误。您在循环外声明并创建了 L。每次添加相同的 L 时，仅使用不同的数据。最后，您得到了在最后一个 foreach 循环中创建的相同数据的列表。

试试这个：

        foreach (var item in db.TempLeaves)
        {
          var z = int.Parse(item.LT) - 1; 
           var L = new Leave{
            Pcode = Int32.Parse(item.Cod),
            LeaveTimeStart = StringToHour(item.LeaveTimeStart),
            LeaveTimeEnd = StringToHour(item.LeaveTimeEnd),
            LeaveDays = int.Parse(item.LeaveDays),
            LT = z == 0? Leave.LeaveType.Saati : Leave.LeaveType.Roozane
            };     
           db.Leaves.Add(L);
        }

或这个

  var leaves= new List<Leave>();
 foreach (var item in db.TempLeaves)
        {
            var z = int.Parse(item.LT) - 1; 
           var L = new Leave{
            Pcode = Int32.Parse(item.Cod),
            LeaveTimeStart = StringToHour(item.LeaveTimeStart),
            LeaveTimeEnd = StringToHour(item.LeaveTimeEnd),
            LeaveDays = int.Parse(item.LeaveDays),
            LT = z == 0? Leave.LeaveType.Saati : Leave.LeaveType.Roozane
             };     
           leaves.Add(L);
        }
   if(leaves.Count>0)
{
   db.Leaves.AddRange(leaves);
  db.SaveChanges();
}

如果你想使用异步保存，你必须先进行异步操作。

Answer 2

每次 foreach 执行 savechnages 的原因是有一个线程不受您的控制。因为 entity framework 正在管理 savechanges 函数。您必须在 foreach 之后执行保存或使用异步函数。

Answer 3

这里是异步的例子：

private static async Task<Student> GetStudent()

{ 学生 student = null;

using (var context = new SchoolDBEntities())
{
    Console.WriteLine("Start GetStudent...");
          
    student = await (context.Students.Where(s => s.StudentID == 1).FirstOrDefaultAsync<Student>());
        
    Console.WriteLine("Finished GetStudent...");
}

return student;

}

Answer 4

*这段代码终于成功了：

public ActionResult FeedTempdataToMainDB()
{
    var leaves = new List<Leave>();
    foreach (var item in db.TempLeaves)
    {
        var L = new Leave();
        L.Pcode = Int32.Parse(item.Cod);
        var z = int.Parse(item.LT) - 1;
        if (z == 0) L.LT = Leave.LeaveType.Saati;
        else L.LT = Leave.LeaveType.Roozane;
        var o = int.Parse(item.DLT);
        if (o == 0) L.DLT = Leave.DLType.Estehghaghi;
        if (o == 1) L.DLT = Leave.DLType.Estelaji;
        else L.DLT = Leave.DLType.Bihoghoogh;
        L.LeaveDayStart = item.LeaveDayStart.Old6digToMiladi();
        L.LeaveDayEnd = item.LeaveDayEnd.Old6digToMiladi();
        L.LeaveTimeStart = StringToHour(item.LeaveTimeStart);
        L.LeaveTimeEnd = StringToHour(item.LeaveTimeEnd);
        L.LeaveDays = int.Parse(item.LeaveDays);
        L.LeaveMinuts = SaatiLengh(item.LeaveMinuts);
        L.RegDate = StringToHour(item.RegTime);
        L.RegDate = item.RegDate.Old6digToMiladi().Date;
        L.RegistrarCode = Int32.Parse(item.RegistrarCode);
        L.HijriYear = L.LeaveDayStart.GetHijriYear();
        var t = IsOk(item.RegTime);
        if (L.DLT == 0 && t == false || L.LT == 0 && t == false)
        {
            L.Calculate = false;

            L.IsActive = false;
        }
        else { L.Calculate = true; L.IsActive = true; }
        leaves.Add(L);
    }

    if (leaves.Count > 0)
    {
        db.Leaves.AddRange(leaves);
        db.SaveChanges();
    }

    return RedirectToAction("index");
}

db.SaveChanges 在 ForEach 中导致 'New transaction is not allowed because there are other threads running in the session'

db.SaveChanges in ForEach causes 'New transaction is not allowed because there are other threads running in the session'

c#

asp.net

model-view-controller

asp.net-mvc

entity-framework