XMLDocument、XMLTextWriter和HttpWebResponse类在.NET核心项目中不起作用

using System.Xml.Linq;

XDocument doc = new XDocument(
    new XElement("Root",
        new XElement("Child", "content")
    )
);

using System.Xml.Linq;

XElement root = new XElement("Root",
    new XElement("Child", "content")
);

using (StringWriter writer = new StringWriter())
{
    root.Save(writer);
    Console.WriteLine(writer.ToString());
}

using System.Net.Http;
using System.Threading.Tasks;

public class HttpClientExample
{
    private static readonly HttpClient client = new HttpClient();

    public static async Task Main()
    {
        HttpResponseMessage response = await client.GetAsync("https://api.example.com/data");
        response.EnsureSuccessStatusCode(); // 抛出异常如果响应状态码不是成功的

        string responseBody = await response.Content.ReadAsStringAsync();
        Console.WriteLine(responseBody);
    }
}

MyProject/
├── MyProject.csproj
├── Program.cs
└── Controllers/
    └── MyController.cs

using System;
using System.Net.Http;
using System.Threading.Tasks;

class Program
{
    private static readonly HttpClient client = new HttpClient();

    static async Task Main(string[] args)
    {
        try
        {
            HttpResponseMessage response = await client.GetAsync("https://api.example.com/data");
            response.EnsureSuccessStatusCode();
            string responseBody = await response.Content.ReadAsStringAsync();
            Console.WriteLine(responseBody);
        }
        catch (Exception ex)
        {
            Console.WriteLine($"An error occurred: {ex.Message}");
        }
    }
}