at Microsoft.EntityFrameworkCore.DbContext.SaveChanges(Boolean acceptAllChangesOnSuccess)
 Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while updating the entries. See the inner exception for details. 
---> System.Data.SqlClient.SqlException: 当 IDENTITY_INSERT 设置为 OFF 时，不能为表 'XXXProjectJF' 中的标识列插入显式值。

                                    c = new ProjectAch();

                                    c.CreateUser = LoginUserId;

                                    c.CreateDate = DateTime.Now;

                                    c.projectJF= _context.ProjectJFs

                                        .Where(t =>t.ProjectName == projectName .AsNoTracking().FirstOrDefault();