LinqDBDataContext lqDB = new LinqDBDataContext(ConfigurationManager.ConnectionStrings["BookConnectionString"].ConnectionString.ToString());
            CategoryDataContext DB = new CategoryDataContext(ConfigurationManager.ConnectionStrings["BookConnectionString"].ConnectionString.ToString());
            var result = from b in lqDB.t_Book join
                          c in DB.Category
                         on b.CategoryName equals c.CategoryName
                         select new { b.CategoryName,c.Age };
            //gvBook.DataKeyNames = new string[] { "ISBN" };
            this.gv.DataSourceID = null;
            this.gv.DataSource = result;
          
            this.gv.DataBind();

我已经将DataSourceIDea设为null

为什么还会出现gv”上同时定义了 DataSource 和 DataSourceID。请移除一个定义