在 JArray 中使用 LINQ

Question

我有一个JSON

{
  "departments": [
    {
      "2": {"city": "Petersburg", "employees": "1200"}
    },
    {
      "1": {"city": "Ekaterinburg", "employees": "4000"}
    }
  ]
}

如果我使用 LINQ 或其他方法知道 ID，我如何获得城市的价值？

我试过了

var id = 2;
json["departments"].Single(x=>x.Name==id.ToString())["city"];

但是它不起作用，我得到一个编译错误：

'JToken' does not contain a definition for 'Name' and no accessible extension method 'Name' accepting a first argument of type 'JToken' could be found (are you missing a using directive or an assembly reference?)

演示 fiddle here.

Answer 1

您的 LINQ 查询可以按如下方式实现：

var id = "2";
var city = (string)json["departments"]
    .Where(o => o[id] != null) // From the departments array, select the object where the required id property exists
    .Select(o => o[id]["city"]).SingleOrDefault(); // An extract the value of "city" from the nested object.

或者，等价地：

var id = "2";
var city = (string)json["departments"]
    .SelectMany(i => i) // Use SelectMany() to project the properties of the array items to a flat enumerable 
    .Cast<JProperty>()  // Cast them to JProperty
    .Where(p => p.Name == id) // Now you can use Name
    .Select(p => p.Value["city"])
    .SingleOrDefault();

或者，您可以使用 SelectToken() 来达到这个目的：

var id = "2";
var path = $"departments[*].{id}.city"; // departments[*].2.city
var city = (string)json.SelectToken(path);

SelectToken()支持JSONPath syntax，[*]是JSONPath通配符，表示搜索所有数组项。

演示 fiddle here.

在 JArray 中使用 LINQ

Using LINQ in JArray

c#

linq

json

json.net