EF4.1中 DBContext.Entry就报错。无法修改数据

Question

DBContext.Entry就报错。无法修改数据
代码如下：
using (HSContext context= new HSContext())
            {                context.DBSet<T>().Attach(entity);
               
                var d = content.Entry(entity);  //context.DBSet<T>().Entry(entity);
                if(d.State== EntityState.Detached)
                    d.State = EntityState.Modified;
  
                content.Entry(entity).State = EntityState.Modified;                
                content.SaveChanges();
                
            }