问题描述

C# |.NET 4.5 |实体框架 5

我有从 SQL 查询返回的 ID、ParentID、Name 形式的数据.我想获取该数据并将其解析为分层 JSON 字符串.到目前为止，这似乎是一项比应有的艰巨任务.由于我使用的是实体，因此数据作为 IEnumerable 很好地返回给我.现在我相信我只需要某种形式的递归，但我不太确定从哪里开始.任何帮助表示赞赏.

数据返回为

代码是

public static string GetJsonLocationHierarchy(long locationID){使用(实体设置上下文 = 新实体设置()){//ID,ParentID,Name 的 IEnumerablecontext.GetLocationHierarchy(locationID);}}

我希望的最终结果是这样的:

<代码>{id":1"，父ID":1"，"名称": "TopLoc",孩子们": [{id":2"，父ID":1"，名称":Loc1"，孩子们": [{id":4"，parentId":2"，名称":Loc1A"，孩子们": [{}]}]},{id":3"，父ID":1"，名称":Loc2"，孩子们": [{}]}]}

将平面表转换为层次结构的一种方法是将所有节点放入字典中.然后遍历字典，并为每个节点查找其父节点并将其添加到父节点的子节点.从那里，您只需要找到根并对其进行序列化.

这是一个演示该方法的示例程序:

类程序{静态无效主要(字符串 [] 参数){IEnumerable<Location>位置=新列表<位置>{新位置 { Id = 1，ParentId = 1，名称 =TopLoc"}，新位置 { Id = 2，ParentId = 1，名称 =Loc1"}，新位置 { Id = 3, ParentId = 1, Name = "Loc2" },新位置 { Id = 4, ParentId = 2, Name = "Loc1A" },};字典<int，位置>dict = locations.ToDictionary(loc => loc.Id);foreach(dict.Values 中的位置 loc){if (loc.ParentId != loc.Id){位置父 = dict[loc.ParentId];父.子.Add(loc);}}位置根 = dict.Values.First(loc => loc.ParentId == loc.Id);JsonSerializerSettings 设置 = 新的 JsonSerializerSettings{ContractResolver = new CamelCasePropertyNamesContractResolver(),格式 = 格式.缩进};字符串 json = JsonConvert.SerializeObject(root, 设置);Console.WriteLine(json);}}上课地点{公共位置(){孩子 = 新列表<位置>();}公共 int ID { 获取；放;}公共 int ParentId { 获取；放;}公共字符串名称 { 获取；放;}公共列表<位置>孩子{得到;放;}}

这是输出:

<代码>{身份证":1，父ID":1，"名称": "TopLoc",孩子们": [{身份证":2，父ID":1，名称":Loc1"，孩子们": [{身份证":4，父ID":2，名称":Loc1A"，孩子们": []}]},{身份证":3，父ID":1，名称":Loc2"，孩子们": []}]}

C# | .NET 4.5 | Entity Framework 5

I have data coming back from a SQL Query in the form of ID,ParentID,Name. I'd like to take that data and parse it into a Hierarchical JSON string. So far it seems to be much more of a daunting task than it should be. Since I'm using Entity the data comes back nicely to me as an IEnumerable. Now I believe I just need some form of recursion, but I'm not quite sure where to start. Any help is appreciated.

Data Returns as

id   parentId    name
1    1           TopLoc
2    1           Loc1
3    1           Loc2
4    2           Loc1A

Code is

public static string GetJsonLocationHierarchy(long locationID)
{
    using (EntitiesSettings context = new EntitiesSettings())
    {
        // IEnumerable of ID,ParentID,Name
        context.GetLocationHierarchy(locationID);
    }
}

The end result I'd hope would be something like this:

{
    "id": "1",
    "parentId": "1",
    "name": "TopLoc",
    "children": [
        {
            "id": "2",
            "parentId": "1",
            "name": "Loc1",
            "children": [
                {
                    "id": "4",
                    "parentId": "2",
                    "name": "Loc1A",
                    "children": [
                        {}
                    ]
                }
            ]
        },
        {
            "id": "3",
            "parentId": "1",
            "name": "Loc2",
            "children": [
                {}
            ]
        }
    ]
}

One way to turn a flat table into a hierarchy is to put all your nodes into a dictionary. Then iterate over the dictionary, and for each node, look up its parent and add it to the parent's children. From there, you just need to find the root and serialize it.

Here is an example program to demonstrate the approach:

class Program
{
    static void Main(string[] args)
    {
        IEnumerable<Location> locations = new List<Location>
        {
            new Location { Id = 1, ParentId = 1, Name = "TopLoc" },
            new Location { Id = 2, ParentId = 1, Name = "Loc1" },
            new Location { Id = 3, ParentId = 1, Name = "Loc2" },
            new Location { Id = 4, ParentId = 2, Name = "Loc1A" },
        };

        Dictionary<int, Location> dict = locations.ToDictionary(loc => loc.Id);

        foreach (Location loc in dict.Values)
        {
            if (loc.ParentId != loc.Id)
            {
                Location parent = dict[loc.ParentId];
                parent.Children.Add(loc);
            }
        }

        Location root = dict.Values.First(loc => loc.ParentId == loc.Id);

        JsonSerializerSettings settings = new JsonSerializerSettings
        {
            ContractResolver = new CamelCasePropertyNamesContractResolver(),
            Formatting = Formatting.Indented
        };
        string json = JsonConvert.SerializeObject(root, settings);

        Console.WriteLine(json);
    }
}

class Location
{
    public Location()
    {
        Children = new List<Location>();
    }

    public int Id { get; set; }
    public int ParentId { get; set; }
    public string Name { get; set; }
    public List<Location> Children { get; set; }
}

Here is the output:

{
  "id": 1,
  "parentId": 1,
  "name": "TopLoc",
  "children": [
    {
      "id": 2,
      "parentId": 1,
      "name": "Loc1",
      "children": [
        {
          "id": 4,
          "parentId": 2,
          "name": "Loc1A",
          "children": []
        }
      ]
    },
    {
      "id": 3,
      "parentId": 1,
      "name": "Loc2",
      "children": []
    }
  ]
}

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