根据条件降序排列答案

【问题标题】：Order by descending based on condition根据条件降序排列
【发布时间】：2010-04-15 07:26:58
【问题描述】：

我想编写一个 LINQ to Entity 查询，它根据输入参数按升序或降序进行排序，有什么办法吗？以下是我的代码。请提出建议。

    public List<Hosters_HostingProviderDetail> GetPendingApproval(SortOrder sortOrder)
    {
        List<Hosters_HostingProviderDetail> returnList = new List<Hosters_HostingProviderDetail>();
        int pendingStateId = Convert.ToInt32(State.Pending);
        //If the sort order is ascending
        if (sortOrder == SortOrder.ASC)
        {
            var hosters = from e in context.Hosters_HostingProviderDetail
                          where e.ActiveStatusID == pendingStateId
                          orderby e.HostingProviderName ascending
                          select e;
            returnList = hosters.ToList<Hosters_HostingProviderDetail>();
            return returnList;
        }
        else
        {
            var hosters = from e in context.Hosters_HostingProviderDetail
                          where e.StateID == pendingStateId
                          orderby e.HostingProviderName descending
                          select e;
            returnList = hosters.ToList<Hosters_HostingProviderDetail>();
            return returnList;
        }
    }

【问题讨论】：

标签： c# asp.net linq linq-to-sql linq-to-entities

【解决方案1】：

我认为您不能将条件放入更大的查询中，但您可以将其分离到另一个 C# 语句中，如下所示：

// Common code:
var hosters = from e in context.Hosters_HostingProviderDetail
              where e.ActiveStatusID == pendingStateId;

// The difference between ASC and DESC:
hosters = (sortOrder == SortOrder.ASC ? hosters.OrderBy(e => e.HostingProviderName) : hosters.OrderByDescending(e => e.HostingProviderName));

// More common code:
returnList = hosters.ToList<Hosters_HostingProviderDetail>();

【讨论】：

【解决方案2】：

你可以用

进一步减少它

var hosters = from e in context.Hosters_HostingProviderDetail
              where e.ActiveStatusID == pendingStateId
              select e;

if (sortOrder == SortOrder.ASC)
   hosters = hosters.OrderBy(e => e.HostingProviderName);
else
    hosters = hosters.OrderByDescending(e => e.HostingProviderName);

return hosters.ToList<Hosters_HostingProviderDetail>();

【讨论】：