netcore入门案例：netcore api连接mysql的完整记事本接口示例

以下是一个使用 .NET Core API 连接 MySQL 数据库实现简单记事本功能的完整示例，包含创建、读取、更新和删除（CRUD）操作。

1. 创建 .NET Core Web API 项目

首先，打开命令行工具，使用以下命令创建一个新的 .NET Core Web API 项目：

dotnet new webapi -n NotePadAPI
cd NotePadAPI

2. 安装 MySQL 数据库驱动

在项目目录下，使用以下命令安装 MySQL 数据库驱动：

dotnet add package MySqlConnector

3. 配置数据库连接字符串

打开 appsettings.json 文件，添加 MySQL 数据库连接字符串：

{
    
    
  "ConnectionStrings": {
    
    
    "DefaultConnection": "Server=localhost;Database=notepad;Uid=your_username;Pwd=your_password;"
  },
  "Logging": {
    
    
    "LogLevel": {
    
    
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*"
}

请将 your_username 和 your_password 替换为你的 MySQL 用户名和密码。

4. 创建数据库和表

在 MySQL 中创建一个名为 notepad 的数据库，并创建一个名为 notes 的表：

CREATE DATABASE notepad;

USE notepad;

CREATE TABLE notes (
    id INT AUTO_INCREMENT PRIMARY KEY,
    title VARCHAR(255) NOT NULL,
    content TEXT NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

5. 创建数据模型

在 Models 文件夹下创建 Note.cs 文件：

using System;

namespace NotePadAPI.Models
{
    
    
    public class Note
    {
    
    
        public int Id {
    
     get; set; }
        public string Title {
    
     get; set; }
        public string Content {
    
     get; set; }
        public DateTime CreatedAt {
    
     get; set; }
    }
}

6. 创建数据库上下文

在 Data 文件夹下创建 NoteContext.cs 文件：

using Microsoft.Data.SqlClient;
using MySqlConnector;
using NotePadAPI.Models;
using System.Collections.Generic;
using System.Data;

namespace NotePadAPI.Data
{
    
    
    public class NoteContext
    {
    
    
        private readonly string _connectionString;

        public NoteContext(string connectionString)
        {
    
    
            _connectionString = connectionString;
        }

        public List<Note> GetAllNotes()
        {
    
    
            var notes = new List<Note>();
            using (var connection = new MySqlConnection(_connectionString))
            {
    
    
                var query = "SELECT * FROM notes";
                var command = new MySqlCommand(query, connection);
                connection.Open();
                var reader = command.ExecuteReader();
                while (reader.Read())
                {
    
    
                    notes.Add(new Note
                    {
    
    
                        Id = reader.GetInt32("id"),
                        Title = reader.GetString("title"),
                        Content = reader.GetString("content"),
                        CreatedAt = reader.GetDateTime("created_at")
                    });
                }
                reader.Close();
            }
            return notes;
        }

        public Note GetNoteById(int id)
        {
    
    
            using (var connection = new MySqlConnection(_connectionString))
            {
    
    
                var query = "SELECT * FROM notes WHERE id = @id";
                var command = new MySqlCommand(query, connection);
                command.Parameters.AddWithValue("@id", id);
                connection.Open();
                var reader = command.ExecuteReader();
                if (reader.Read())
                {
    
    
                    return new Note
                    {
    
    
                        Id = reader.GetInt32("id"),
                        Title = reader.GetString("title"),
                        Content = reader.GetString("content"),
                        CreatedAt = reader.GetDateTime("created_at")
                    };
                }
                reader.Close();
            }
            return null;
        }

        public void CreateNote(Note note)
        {
    
    
            using (var connection = new MySqlConnection(_connectionString))
            {
    
    
                var query = "INSERT INTO notes (title, content) VALUES (@title, @content)";
                var command = new MySqlCommand(query, connection);
                command.Parameters.AddWithValue("@title", note.Title);
                command.Parameters.AddWithValue("@content", note.Content);
                connection.Open();
                command.ExecuteNonQuery();
            }
        }

        public void UpdateNote(Note note)
        {
    
    
            using (var connection = new MySqlConnection(_connectionString))
            {
    
    
                var query = "UPDATE notes SET title = @title, content = @content WHERE id = @id";
                var command = new MySqlCommand(query, connection);
                command.Parameters.AddWithValue("@title", note.Title);
                command.Parameters.AddWithValue("@content", note.Content);
                command.Parameters.AddWithValue("@id", note.Id);
                connection.Open();
                command.ExecuteNonQuery();
            }
        }

        public void DeleteNote(int id)
        {
    
    
            using (var connection = new MySqlConnection(_connectionString))
            {
    
    
                var query = "DELETE FROM notes WHERE id = @id";
                var command = new MySqlCommand(query, connection);
                command.Parameters.AddWithValue("@id", id);
                connection.Open();
                command.ExecuteNonQuery();
            }
        }
    }
}

7. 创建控制器

在 Controllers 文件夹下创建 NotesController.cs 文件：

using Microsoft.AspNetCore.Mvc;
using NotePadAPI.Data;
using NotePadAPI.Models;
using System.Collections.Generic;

namespace NotePadAPI.Controllers
{
    
    
    [ApiController]
    [Route("api/[controller]")]
    public class NotesController : ControllerBase
    {
    
    
        private readonly NoteContext _context;

        public NotesController(NoteContext context)
        {
    
    
            _context = context;
        }

        [HttpGet]
        public ActionResult<IEnumerable<Note>> GetAllNotes()
        {
    
    
            var notes = _context.GetAllNotes();
            return Ok(notes);
        }

        [HttpGet("{id}")]
        public ActionResult<Note> GetNoteById(int id)
        {
    
    
            var note = _context.GetNoteById(id);
            if (note == null)
            {
    
    
                return NotFound();
            }
            return Ok(note);
        }

        [HttpPost]
        public ActionResult<Note> CreateNote(Note note)
        {
    
    
            _context.CreateNote(note);
            return CreatedAtAction(nameof(GetNoteById), new {
    
     id = note.Id }, note);
        }

        [HttpPut("{id}")]
        public IActionResult UpdateNote(int id, Note note)
        {
    
    
            if (id != note.Id)
            {
    
    
                return BadRequest();
            }
            _context.UpdateNote(note);
            return NoContent();
        }

        [HttpDelete("{id}")]
        public IActionResult DeleteNote(int id)
        {
    
    
            _context.DeleteNote(id);
            return NoContent();
        }
    }
}

8. 配置服务

打开 Program.cs 文件，配置数据库上下文：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using NotePadAPI.Data;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

// Configure database context
var connectionString = builder.Configuration.GetConnectionString("DefaultConnection");
builder.Services.AddSingleton(new NoteContext(connectionString));

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    
    
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

9. 运行项目

在命令行中运行以下命令启动项目：

dotnet run

10. 测试 API

你可以使用 Postman 或其他 API 测试工具来测试以下接口：

获取所有笔记：GET http://localhost:5000/api/notes
获取单个笔记：GET http://localhost:5000/api/notes/{id}
创建笔记：POST http://localhost:5000/api/notes，请求体为 JSON 格式的笔记信息。
更新笔记：PUT http://localhost:5000/api/notes/{id}，请求体为 JSON 格式的更新后的笔记信息。
删除笔记：DELETE http://localhost:5000/api/notes/{id}

通过以上步骤，你就可以实现一个简单的记事本 API，使用 .NET Core 连接 MySQL 数据库进行数据的 CRUD 操作。