排序字段其在LINQ

Question

由3个个子串我有如下LINQ查询，

var sortedResults = (from r in this.CurrentTemplateInfos 
         where r.EffectiveEnd == null 
         orderby r.Description 
         select r); 

从上述查询，字段说明由通过科隆(:)分离3个个子串(Showtype:Show:StartDate-Endate)。现在根据新的要求i需要通过升序前两个fields(Showtype:Show)并从StartDate降低的描述值，例如，

Show : Main Street Trolley : 6/12/2010 - 7/15/2010 

ShowType : Parades : 2/10/2010 - 6/16/2010 

ShowType : Parades : 6/17/2010 - 8/26/2010 

ShowType : Parades : 8/27/2010 - 10/26/2010 

输出应该是

Show : Main Street Trolley : 6/12/2010 - 7/15/2010 

ShowType :Parades : 8/27/2010 - 10/26/2010 

ShowType : Parades : 6/17/2010 - 8/26/2010 

ShowType : Parades : 2/10/2010 - 6/16/2010 

请帮助我在此。

Answer 1

使用助手类型将字段分成不同的字段，然后按子句的顺序使用该字段。喜欢的东西：

// Elsewhere 
class SortFields { 
    public string Field1 { get; set; } 
    public string Field2 { get; set; } 
    public DateTime StartDate { get; set; } 

    public static SortFields SplitInput(string input) { 
    // Factory... Implement split/parse logic 
    } 
} 

然后

from r in this.CurrentTemplateInfos 
where r.EffectiveEnd == null 
let fields = SortField.SplitInput(r.Description) 
// This means sort by Field1, then Field2 and then StartDate 
// and the default in each criterion is ascending unless you 
// specify descending keyword. 
orderby fields.Field1, fields.Field2, fields.StartDate descending 
select r 

注意，可以使用使用多个let条款做了分流/解析，但我认为小帮手型更清晰。

Answer 2

var sortedResults = from r in this.CurrentTemplateInfos 
        where r.EffectiveEnd == null 
        let parts = r.Description.Split(':') 
        let firstPart = parts[0] + parts[1] 
        let startDate = DateTime.Parse(parts[2].Split('-').First().Trim()) 
        orderby firstPart, startDate descending 
        select r;