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如何将LINQ到SQL分组结果映射到此现有接口?

linq-to-sql linq c#

Chris Farmer Marcelo Cantos · 技术社区 · 15 年前

我有一个Linq to SQL查询,它返回 Sponsor 这样的对象:

var result = ( from s in db.Sponsors
               join sl in sb.SponsorLevels on s.SponsorLevelId equals sl.SponsorLevelId
               select new Sponsor 
               {
                 Name = s.Name,
                 Level = sl.LevelName
               }
             ).GroupBy(s => s.LevelName);

我的应用程序已使用定义为…

public interface ISponsorLevelGroup
{
    string Level { get; set; }
    IList<Sponsor> Sponsors { get; set; }
}

……在哪里 Level String属性是Linq结果的分组键。我最终想把LINQ结果变成 IList<ISponsorLevelGroup> .

逻辑上,我的linq to sql结果是 ISponsorLevelGroup 对象,但我不确定如何最有效地将一个映射到另一个。此时,我似乎被降级为手动遍历组及其内部的集合,并将数据复制到实现特定接口的对象中。有更好的方法吗?如何最有效地将LINQ结果 iList<isMonsorLevelGroup> ?

2 回复 | 直到 15 年前

Ian Johnson 15 年前

你试过了吗?

private class SponsorLevelGroup : ISponsorLevelGroup
{
   public string Level { get; set; }
   public IList<Sponsor> Sponsors { get; set; }
}

var result = ( from s in db.Sponsors
               join sl in sb.SponsorLevels on s.SponsorLevelId equals sl.SponsorLevelId
               select new Sponsor 
               {
                 Name = s.Name,
                 Level = sl.LevelName
               }
             ).GroupBy(s => s.LevelName)
              .Select(g => new SponsorLevelGroup
                               {
                                   Level = g.Key,
                                   Sponsors = g.ToList()
                                }) ;

这将返回一个集合isponsorLevelGroup对象

bruno conde 15 年前

这就是你需要的吗?我没有像你一样创建一个新的赞助商类。看看这是否合理。

    public class Sponsor
    {
        public int SponsorLevelId { get; set; }
        public string Name { get; set; }

        public override string ToString()
        {
            return string.Format("Name: {0}", Name);
        }
    }

    public class SponsorLevel
    {
        public int SponsorLevelId { get; set; }
        public string LevelName { get; set; }
    }

    public class SponsorLevelGroup
    {
        public string Level { get; set; }
        public IList<Sponsor> Sponsors { get; set; }

        public override string ToString()
        {
            return string.Format("Level: {0} Sponsors: {1}", Level, Sponsors.Count);
        }
    }

    static void Main(string[] args)
    {
        List<Sponsor> sponsors = new List<Sponsor>()
        {
            new Sponsor { SponsorLevelId = 1, Name = "A" },
            new Sponsor { SponsorLevelId = 2, Name = "B" },
            new Sponsor { SponsorLevelId = 1, Name = "C" },
            new Sponsor { SponsorLevelId = 3, Name = "D" }
        };

        List<SponsorLevel> sponsorLevels = new List<SponsorLevel>()
        {
            new SponsorLevel { SponsorLevelId = 1, LevelName = "L1" },
            new SponsorLevel { SponsorLevelId = 2, LevelName = "L2" },
            new SponsorLevel { SponsorLevelId = 3, LevelName = "L3" }
        };

        var result = (from s in sponsors
                      join sl in sponsorLevels on s.SponsorLevelId equals sl.SponsorLevelId
                      group s by sl.LevelName into g
                      select new SponsorLevelGroup
                      {
                          Level = g.Key,
                          Sponsors = g.ToList()
                      }
         );

        foreach (var r in result)
        {
            Console.WriteLine(r);
        }
     }

印刷品:

Level: L1 Sponsors: 2
Level: L2 Sponsors: 1
Level: L3 Sponsors: 1