MVC EF 修改某些值

 我这里是不修改创建时间,和创建人 ..其它的都修改.

DbEntityEntry<JF_Tasks> entry = db.Entry<JF_Tasks>(jf_tasks);
entry.State = EntityState.Modified;   //全更新
entry.Property(a => a.CreatedOn).IsModified = false; //设置不更新的值
entry.Property(a => a.CreatedBy).IsModified = false;
await db.SaveChangesAsync();

 只修改删除标记

message.isdelete = true;
DbEntityEntry<message> entry = db.Entry(message);
entry.State = EntityState.Unchanged; //全不更新
entry.Property(m => m.isdelete).IsModified = true; //设置要更新的属性