通用类型JsonConvert.DeserializeObject< List< T>>(字符串) [英] Generic Type JsonConvert.DeserializeObject<List<T>>(string)

问题描述

我正在使用Newtonsoft.JSON.我不知道传递给此方法或检索到该方法的对象的类型，所以我尝试在不知道其类型的对象上使用DeserializeObject.

I am using Newtonsoft.JSON. I won't know the type of object passed to this method, or retrieved to this method, so I am attempting to use DeserializeObject on an object I do not know the type of.

这可能吗?如果是这样，怎么办? 这是我的代码.

Is this possible? If so, how? Here is my code.

public static List<T> GetObject<T>(string cacheKey, IEnumerable<T> obj)
{
    using (HttpClient client = new HttpClient())
    {
        var response = client.GetAsync("http://localhost:53805/api/NonPersisted/Get/" + cacheKey).Result;

        obj = JsonConvert.DeserializeObject<obj.GetType>(response.Content.ToString());
        return obj.ToList();
    }            
}

我首先尝试使用

obj = JsonConvert.DeserializeObject<List<T>>(response.Content.ToString());

这显然行不通，无法解析. obj is a variable but used like a type.

This didn't work, obviously, it was unable to parse. Getting the Type of the object won't build, it says obj is a variable but used like a type.

编辑 似乎可以使用通用List<T>而不用JsonConvert.DeserializeObject<>知道类型.真正的错误是response.Content仅返回类型.你需要...

EDIT It appears you can use a generic List<T> without knowing the type with JsonConvert.DeserializeObject<> The real error was that the response.Content was only returning the type. You need to have...

obj = JsonConvert.DeserializeObject<List<T>>(response.Content.ReadAsStringAsync().Result);

推荐答案

您可以使GetObject方法通用，而无需使用参数IEnumerable<T> obj.

You can make GetObject method generic without having parameter IEnumerable<T> obj.

以下解决方案是建议您假设您知道从URL返回的JSON值的格式.

Following solution I am suggesting with assumption that you know the format of the JSON value being returned from the URL.

例如，URL返回包含项目数组的JSON，并且每个项目都有两个属性firstName和lastName.

For example, that the URL returns JSON which contains array of items and each item has two properties firstName and lastName.

var response = "[{\"firstName\":\"Melanie\",\"lastName\":\"Acevedo\"},
    {\"firstName\":\"Rich\",\"lastName\":\"Garrett\"},
    {\"firstName\":\"Dominguez\",\"lastName\":\"Rose\"},
    {\"firstName\":\"Louisa\",\"lastName\":\"Howell\"},
    {\"firstName\":\"Stone\",\"lastName\":\"Bean\"},
    {\"firstName\":\"Karen\",\"lastName\":\"Buckley\"}]";

我可以编写如下的GetObject方法.

I can write GetObject method as following.

public static List<T> GetObject<T>()
{
    var response = "
        [{\"firstName\":\"Melanie\",\"lastName\":\"Acevedo\"},
        {\"firstName\":\"Rich\",\"lastName\":\"Garrett\"},
        {\"firstName\":\"Dominguez\",\"lastName\":\"Rose\"},
        {\"firstName\":\"Louisa\",\"lastName\":\"Howell\"},
        {\"firstName\":\"Stone\",\"lastName\":\"Bean\"},
        {\"firstName\":\"Karen\",\"lastName\":\"Buckley\"}]";

    var obj = JsonConvert.DeserializeObject<List<T>>(response);
        return obj.ToList();
}

在上述方法中的T可以具有属性firstName和lastName的任何类型.例如

Here T in above method can by any type which has properties firstName and lastName. For example

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public DateTime DateOfBirth { get; set; }
}

public class Employee
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public double Salary { get; set; }
}

我可以通过传递Person或Employee来调用GetObject方法，如下所示将JSON字符串反序列化到这些类的对象集合中.

I can call GetObject method by passing either Person or Employee and get the JSON string deserialize to the collection of objects of these classes as following.

var persons = GetObject<Person>();

foreach (var item in persons)
{
    Console.WriteLine($"{item.FirstName} {item.LastName}");
}

var employees = GetObject<Employee>();

foreach (var item in employees)
{
    Console.WriteLine($"{item.FirstName} {item.LastName}");
}

总的来说，我要说的是，如果知道JSON格式，则可以将适当的Type传递给JsonConvert.Deserialize<T>应该可以正常工作.

Overall, the point I am trying to make is if format of the JSON is know the passing appropriate Type to JsonConvert.Deserialize<T> should work without any problem.

如果传入的JSON表示一个集合，并且尝试将其反序列化为一个简单的类将失败，反之亦然.

If incoming JSON represents a collection and trying to deserialize it to a simple class would fail and vice versa too will not work.

所以对于您的问题，如果您知道JSON将成为一个集合，那么使用JsonConvert.Deserialize<List<T>>应该不会给您带来任何问题，只要T具有可以设置JSON值的属性即可.

So for your problem, if you know that JSON is going to be a collection then using JsonConvert.Deserialize<List<T>> should not give you any problem as long T has the properties to which values from JSON can be set.

我希望这可以帮助您解决问题.

I hope this would help you resolve your issue.

这篇关于通用类型JsonConvert.DeserializeObject< List< T>>(字符串)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！