LINQ orderby 排序妙用

做排序，项目中发现好多地方要用到排序，什么正序、倒序、写的很累，不过为发现排序写一个综合方法很不错的

1、得到某某的数据

　　IEnumerable<xxxx> = .....................;

2、得到要排序的参数orderby

　　orderby参数格式：

　　orderby = "CreateTime asc,Title desc";

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　　OrderUsingSortExpression(res.AsQueryable(), orderby).AsEnumerable();

3、对数据进行排序的方法

　　   public static IOrderedQueryable<TEntity> OrderUsingSortExpression<TEntity>(this IQueryable<TEntity> source, string sortExpression) where TEntity : class
        {
            String[] orderFields = sortExpression.Split(',');
            IOrderedQueryable<TEntity> result = null;
            for (int currentFieldIndex = 0; currentFieldIndex < orderFields.Length; currentFieldIndex++)
            {
                String[] expressionPart = orderFields[currentFieldIndex].Trim().Split(' ');
                String sortField = expressionPart[0];
                Boolean sortDescending = (expressionPart.Length == 2) && (expressionPart[1].Equals("DESC", StringComparison.OrdinalIgnoreCase));
                if (sortDescending)
                {
                    result = currentFieldIndex == 0 ? source.OrderByDescending(sortField) : result.ThenByDescending(sortField);
                }
                else
                {
                    result = currentFieldIndex == 0 ? source.OrderBy(sortField) : result.ThenBy(sortField);
                }
            }
            return result;
        }

　　4、这样所有的后台方法不论排序有多少个，只用定义一个orderby参数，按照一定的规格就好了