原因是返回值显示3，初步判断是Add(entity)方法出错。之后查询MSDN，也无法获得满意的答复，所以在博问上讨教各位：为能够正常插入数据，Add(entity)的错误应该怎么样排除？

public override int Add(ExprmntUser entity, bool isExecute = true)
        {
            try
            {
                
                _DbSet.Add(entity);
                
                if (isExecute)
                {
                    //return _DbContext.SaveChanges() > 0;
                    _DbContext.SaveChanges();
                    return 1;
                }
                else
                {
                    //return true;
                    return 2;
                }
            }
            catch
            {
                //return false;
                return 3;
            }
        }