/// <summary>
 /// 把IOrderedQueryable集合按照指定的属性与排序方式进行排序
 /// </summary>
 /// <typeparam name="T">数据集类型</typeparam>
 /// <param name="source">要排序的数据集</param>
 /// <param name="sortCondition">排序条件</param>
 /// <returns>返回排序后的结果集</returns>
 public static IOrderedQueryable <T> ThenBy <T>(this IOrderedQueryable <T> source, PropertySortCondition sortCondition)
 {
     if (sortCondition.CheckArgument("sortCondition"))
     {
         return(QueryableHelper <T> .ThenBy(source, sortCondition.PropertyName, sortCondition.ListSortDirection));
     }
     return(null);
 }
 /// <summary>
 /// 把IQueryable集合按照指定的属性与排序方式进行排序
 /// </summary>
 /// <typeparam name="T">数据集类型</typeparam>
 /// <param name="source">要排序的数据集</param>
 /// <param name="propName">要排序的属性名称</param>
 /// <param name="listSort">排序方式</param>
 /// <returns>返回排序后的结果集</returns>
 public static IOrderedQueryable <T> OrderBy <T>(this IQueryable <T> source, string propName,
                                                 ListSortDirection listSort = ListSortDirection.Ascending)
 {
     if (propName.CheckArgument("propName"))
     {
         return(QueryableHelper <T> .OrderBy(source, propName, listSort));
     }
     return(null);
 }