2 Batch deletion     db.T_Investigator.RemoveRange(list)

3 Bulk changes    for Cyclic modification .

Be careful ： Find out first , Last savechange（）, Written in a transaction , One context at a time .

 public int SubmitAll(int[] idList, int userId)
{
int num = 0;
using (var pmdb = new ProjectManagementEntities())
{
using (var tran = pmdb.Database.BeginTransaction())
{
try
{
var list = pmdb.T_Investigator.Where(d => idList.Contains(d.InvestigatorID) && d.CreateUserID == userId && d.HasSubmitted == false).ToList();
if (list.Count > 0)
{
foreach (var item in list)
{
item.HasSubmitted = true;
}
num = pmdb.SaveChanges();
tran.Commit();
}
}
catch (Exception ex)
{
tran.Rollback();// Roll back
throw ex;
}
}
}
return num;
}


Online cases ：

EF Those batch operations in

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