五、.Net Core Web Api连接MongoDB自动创建表格并实现CRUD功能

1.注册MongoDB账号，并获取Connection String；

MongoDB官网：MongoDB: The Developer Data Platform | MongoDB

获取Connection String教程：Connection String 获取

在VSCode for Mac按下shift+command+p搜索 Nuget Package Manager: Add Package，给项目添加包

搜索包：MongoDB.Driver，Microsoft.EntityFrameworkCore，MongoDB.EntityFrameworkCore

MongoDB.Driver选择最新版本即可，如最新版本不适配您当前的.Net版本，请尝试根据MongoDB官网有关MongoDB.Driver的兼容性来进行安装：兼容性 - C#/.NET v2.28 (mongodb.com)；

Microsoft.EntityFrameworkCore和MongoDB.EntityFrameworkCore包选择8.x版本。

在Web Api的appsetting.Development.json 添加MongoDB信息，在ConnectionString的值中填入在MongoDB官网获取的ConnectionString；

<code>{ -- -->

"Logging": {

"LogLevel": {

"Default": "Information",

"Microsoft.AspNetCore": "Warning"

}

},

"TeachingAppDatabase": {

"BooksCollectionName": "books",

"ConnectionString": "Fill it with your MongoDB connection string",

"DatabaseName": "teaching_blazor_app"

}

}

创建Config/MongoDbConfiguration.cs，对应appsettings.Development.json中的参数。

using System;

namespace TeachingWebApi.Config

{

public class TeachingAppDatabaseSettings

{

public string BooksCollectionName { get; init; }

public string ConnectionString { get; init; }

public string DatabaseName { get; init; }

}

}

在Program.cs中加入以下服务，通过IConfiguration读取appsettings.Development.json中的参数。

builder.Services.Configure<TeachingAppDatabaseSettings>(

builder.Configuration.GetSection("TeachingAppDatabase"));

创建BookService.cs添加 CRUD 操作服务.

using Microsoft.Extensions.Options;

using MongoDB.Driver;

using TeachingWebApi.Config;

using TeachingWebApi.Models;

namespace TeachingWebApi.Services;

public class BooksService

{

private readonly IMongoCollection<Book> _booksCollection;

public BooksService(

IOptions<TeachingAppDatabaseSettings> mongoDatabaseSettings)

{

var mongoClient = new MongoClient(

mongoDatabaseSettings.Value.ConnectionString);

var mongoDatabase = mongoClient.GetDatabase(

mongoDatabaseSettings.Value.DatabaseName);

_booksCollection = mongoDatabase.GetCollection<Book>(

mongoDatabaseSettings.Value.BooksCollectionName);

}

public async Task<List<Book>> GetAsync() =>

await _booksCollection.Find(_ => true).ToListAsync();

public async Task<Book?> GetAsync(string id) =>

await _booksCollection.Find(x => x.Id == id).FirstOrDefaultAsync();

public async Task CreateAsync(Book newBook) =>

await _booksCollection.InsertOneAsync(newBook);

public async Task UpdateAsync(string id, Book updatedBook) =>

await _booksCollection.ReplaceOneAsync(x => x.Id == id, updatedBook);

public async Task RemoveAsync(string id) =>

await _booksCollection.DeleteOneAsync(x => x.Id == id);

}

新建一个BookController.cs，实现CRUD；

using Microsoft.AspNetCore.Mvc;

using TeachingWebApi.Models;

using TeachingWebApi.Services;

namespace BookStoreApi.Controllers;

[ApiController]

[Route("api/[controller]")]

public class BooksController : ControllerBase

{

private readonly BooksService _booksService;

public BooksController(BooksService booksService) =>

_booksService = booksService;

[HttpGet]

public async Task<List<Book>> Get() =>

await _booksService.GetAsync();

[HttpGet("{id:length(24)}")]

public async Task<ActionResult<Book>> Get(string id)

{

var book = await _booksService.GetAsync(id);

if (book is null)

{

return NotFound();

}

return book;

}

[HttpPost]

public async Task<IActionResult> Post(Book newBook)

{

await _booksService.CreateAsync(newBook);

return CreatedAtAction(nameof(Get), new { id = newBook.Id }, newBook);

}

[HttpPut("{id:length(24)}")]

public async Task<IActionResult> Update(string id, Book updatedBook)

{

var book = await _booksService.GetAsync(id);

if (book is null)

{

return NotFound();

}

updatedBook.Id = book.Id;

await _booksService.UpdateAsync(id, updatedBook);

return NoContent();

}

[HttpDelete("{id:length(24)}")]

public async Task<IActionResult> Delete(string id)

{

var book = await _booksService.GetAsync(id);

if (book is null)

{

return NotFound();

}

await _booksService.RemoveAsync(id);

return NoContent();

}

}

添加代码到Program.cs，以向 DI 注册 BooksService 类，以支持消费类中的构造函数注入。 单一实例服务生存期是最合适的，因为 BooksService 直接依赖于 MongoClient。 根据官方 Mongo Client 重用准则，应使用单一实例服务生存期在 DI 中注册 MongoClient。

builder.Services.AddSingleton<BooksService>();

新建类MongoDBContext.cs，负责连接MongoDB的上下文类；

using Microsoft.EntityFrameworkCore;

using Microsoft.Extensions.Options;

using MongoDB.Driver;

using TeachingWebApi.Config;

using TeachingWebApi.Models;

namespace TeachingWebApi.Utils.Data

{

public class MongoDbContext : DbContext

{

public readonly IMongoDatabase _db;

private readonly string _booksCollectionName;

private readonly IOptions<TeachingAppDatabaseSettings> _setting;

public MongoDbContext(IOptions<TeachingAppDatabaseSettings> setting)

{

_setting = setting;

var client = new MongoClient(_setting.Value.ConnectionString);

_db = client.GetDatabase(_setting.Value.DatabaseName);

_booksCollectionName = _setting.Value.BooksCollectionName;

}

public IMongoCollection<Book> Books =>

_db.GetCollection<Book>(_booksCollectionName);

}

}

添加类DatabaseSeeder.cs，负责初始化数据库；

using Microsoft.Extensions.Localization;

using Microsoft.AspNetCore.Identity;

using MongoDB.Driver;

using TeachingWebApi.Utils.Data;

namespace CoolWebApi.Data.Seeder

{

public class DatabaseSeeder

{

private readonly MongoDbContext _dbContext;

public DatabaseSeeder(

MongoDbContext dbContext)

{

_dbContext = dbContext;

}

public void Initialize()

{

InitializeCollection();

}

public async void InitializeCollection()

{

await CreateCollection("books");

}

private async Task CreateCollection(string collectionName)

{

if (!CollectionExists(_dbContext._db, collectionName))

{

await _dbContext._db.CreateCollectionAsync(collectionName, new CreateCollectionOptions

{

Capped = false

});

Console.WriteLine("Collection created!");

}

}

private bool CollectionExists(IMongoDatabase database, string collectionName)

{

return database.ListCollectionNames().ToList().Contains(collectionName);

}

}

}

在Program.cs添加数据库支持，使用Microsoft.EntityFrameworkCore和MongoDB.EntityFrameworkCore包，当项目运行时会执行DatabaseSeeder.cs和MongoDbContext.cs这两个类，实现初始化项目时生成数据库表；

builder.Services

.AddTransient<DatabaseSeeder>()

.AddDbContext<MongoDbContext>(options => options

.UseMongoDB(new MongoClient(MongoDbConectionString), "teaching_blazor_app"));

运行应用，记得将ConnectionString里的改成自己的密码，不然会报认证失败的错误；

可以看到MongoDB的Collections已经自动生成了Books表，使用Swagger进行测试；