C#http协议实现数据库增删改查

以下是一个简单的 C# 程序，通过 http 协议实现增删改查数据库：

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

namespace HttpClientExample
{
    class Program
    {
        static HttpClient client = new HttpClient();

        static void Main(string[] args)
        {
            client.BaseAddress = new Uri("http://localhost:5000/");
            client.DefaultRequestHeaders.Accept.Clear();
            client.DefaultRequestHeaders.Accept.Add(
                new MediaTypeWithQualityHeaderValue("application/json"));

            RunAsync().Wait();
        }

        static async Task RunAsync()
        {
            try
            {
                // 创建一个新用户
                User user = new User() { Name = "Tom", Age = 20 };
                await CreateUserAsync(user);

                // 获取用户列表
                await GetUsersAsync();

                // 更新用户信息
                user.Age = 21;
                await UpdateUserAsync(user);

                // 获取单个用户信息
                await GetUserAsync(user.Id);

                // 删除用户
                await DeleteUserAsync(user.Id);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }

            Console.ReadLine();
        }

        static async Task CreateUserAsync(User user)
        {
            HttpResponseMessage response = await client.PostAsJsonAsync(
                "api/users", user);
            response.EnsureSuccessStatusCode();

            user = await response.Content.ReadAsAsync<User>();

            Console.WriteLine($"Created user with id: {user.Id}");
        }

        static async Task UpdateUserAsync(User user)
        {
            HttpResponseMessage response = await client.PutAsJsonAsync(
                $"api/users/{user.Id}", user);
            response.EnsureSuccessStatusCode();

            user = await response.Content.ReadAsAsync<User>();

            Console.WriteLine($"Updated user {user.Id}");
        }

        static async Task DeleteUserAsync(int id)
        {
            HttpResponseMessage response = await client.DeleteAsync(
                $"api/users/{id}");
            response.EnsureSuccessStatusCode();

            Console.WriteLine($"Deleted user {id}");
        }

        static async Task GetUsersAsync()
        {
            HttpResponseMessage response = await client.GetAsync("api/users");
            response.EnsureSuccessStatusCode();

            var users = await response.Content.ReadAsAsync<User[]>();

            Console.WriteLine("Users:");
            foreach (var user in users)
            {
                Console.WriteLine($"Id: {user.Id}, Name: {user.Name}, Age: {user.Age}");
            }
        }

        static async Task GetUserAsync(int id)
        {
            HttpResponseMessage response = await client.GetAsync($"api/users/{id}");
            response.EnsureSuccessStatusCode();

            var user = await response.Content.ReadAsAsync<User>();

            Console.WriteLine($"User: Id: {user.Id}, Name: {user.Name}, Age: {user.Age}");
        }
    }
}

上述代码中，`User` 类是一个简单的数据模型，包含 `Id`，`Name` 和 `Age` 三个属性。通过 http 协议，我们可以向服务端发送 POST、PUT、DELETE 和 GET 请求，来实现增删改查操作。

服务端的代码实现可以参考以下示例：

using System.Collections.Generic;
using Microsoft.AspNetCore.Mvc;

namespace WebApiExample.Controllers
{
    [ApiController]
    [Route("api/[controller]")]
    public class UsersController : ControllerBase
    {
        private static readonly List<User> Users = new List<User>();

        [HttpGet]
        public IEnumerable<User> GetAll()
        {
            return Users;
        }

        [HttpGet("{id}")]
        public ActionResult<User> GetById(int id)
        {
            var user = Users.Find(u => u.Id == id);
            if (user == null)
            {
                return NotFound();
            }
            return user;
        }

        [HttpPost]
        public ActionResult<User> Create(User user)
        {
            user.Id = Users.Count + 1;
            Users.Add(user);

            return CreatedAtAction(nameof(GetById), new { id = user.Id }, user);
        }

        [HttpPut("{id}")]
        public IActionResult Update(int id, User user)
        {
            var existingUser = Users.Find(u => u.Id == id);
            if (existingUser == null)
            {
                return NotFound();
            }

            existingUser.Name = user.Name;
            existingUser.Age = user.Age;

            return NoContent();
        }

        [HttpDelete("{id}")]
        public IActionResult Delete(int id)
        {
            var user = Users.Find(u => u.Id == id);
            if (user == null)
            {
                return NotFound();
            }

            Users.Remove(user);

            return NoContent();
        }
    }

    public class User
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
    }
}

上述代码中，我们通过 ASP.NET Core 的 Web API 实现了一个简单的用户管理服务，包含 GET、POST、PUT 和 DELETE 四个接口，用于增删改查用户信息。服务端监听的端口是 `5000`。