C# + EntityFramework：通过查询将多个组转换为嵌套 JSON

Posted 2023-04-12

【中文标题】C# + EntityFramework：通过查询将多个组转换为嵌套 JSON

【英文标题】：C# + EntityFramework: Convert multiple group by query to nested JSON

【发布时间】：2015-09-12 14:51:40

【问题描述】：

我做了以下 linq 声明

C#

var list = from row in repository.GetAllEntities()
                       group row by new  row.RegionString, row.SubRegionString, row.CountryString  into g
                       select new  g.Key.RegionString, g.Key.SubRegionString, g.Key.CountryString, Count = g.Count() ;

return Json(list, JsonRequestBehavior.AllowGet);

返回

[
  
    "RegionString":"Americas",
    "SubRegionString":"",
    "CountryString":"",
    "Count":2
  ,
  
    "RegionString":"Americas",
    "SubRegionString":"NorthAmerica",
    "CountryString":"Canada",
    "Count":5
  ,
  
    "RegionString":"Americas",
    "SubRegionString":"NorthAmerica",
    "CountryString":"US",
    "Count":3
  ,
  
    "RegionString":"Americas",
    "SubRegionString":"SouthAmerica",
    "CountryString":"Chile",
    "Count":3
  ,
  
    "RegionString":"EMEA",
    "SubRegionString":"AsiaPacific",
    "CountryString":"Australia",
    "Count":2
  ,
  
    "RegionString":"EMEA",
    "SubRegionString":"AsiaPacific",
    "CountryString":"Japan",
    "Count":1
  ,
  
    "RegionString":"EMEA",
    "SubRegionString":"SouthernEurope",
    "CountryString":"Turkey",
    "Count":1
  ,
  
    "RegionString":"EMEA",
    "SubRegionString":"WesternEurope",
    "CountryString":"",
    "Count":1
  
]

但我正在尝试将其变成这种格式

[
    name: "Americas",
    children: [
     
         name: "NorthAmerica",
         children: [ "name": "Canada", "count": 5 ,
                     "name": "US", "count": 3 ]

     ,
     
         name: "SouthAmerica",
         children: [ "name": "Chile", "count": 1 ]
     ,
    ],
,

    name: "EMA",
    children: [
     
         name: "AsiaPacific",
         children: [ "name": "Australia", "count": 2 ,
                     "name": "Japan", "count": 1 ]

     ,
     
         name: "SouthernEurope",
         children: [ "name": "Turkey", "count": 1 ]
     ,
    ],
]

如何修改语句以获得我正在寻找的结果？非 linq 答案也是可以接受的。

编辑： Region 是 SubRegion 的父级，SubRegion 是 Country 的父级，Count 是属于 Country 的唯一项目数

【问题讨论】：

你能解释一下除了格式之外你想做什么吗？ IE。子区域是区域字符串的子区域

刚刚用层次结构编辑了答案。希望这会有所帮助

你可以用我现在正在尝试解决的字典字典来做到这一点

【参考方案1】：

这是您想要的 linq 查询（为了便于阅读，我删除了 -String 后缀）：

var list =
    from entity in repository.GetAllEntities()
    group entity by entity.Region into regions
    let childrenOfRegions =
        from region in regions
        group region by region.SubRegion into subregions
        let countriesOfSubRegions =
            from subregion in subregions
            group subregion by subregion.Country into countries
            select new  Name = countries.Key 
        select new  Name = subregions.Key, Children = countriesOfSubRegions 
    select new  Name = regions.Key, Children = childrenOfRegions ;  

这个查询中没有Count，因为我不太明白你在数什么。

我在这里所做的是将行分组到区域中，在最后一行中，您可以看到 select new Name = regions.Key, ... 我返回区域的部分。 要获得孩子，您需要将区域分组为子区域（与区域相同）。你一直重复这个到国家，你就完成了。