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话不多说，先了解一下MongoDB，在后端服务中选择一个数据库，是由最适合项目应用场景的架构决策所决定的。在做出决策前就需要了解和学习数据库的相关特性，从数据库官网学习了解它的特性是最适合不过的了。

MongoDB官方手册网站：MongoDB是什么？ - 数据库手册 - MongoDB Docs

MongoDB .NET/C# 驱动程序手册网站：快速入门 - C#/.NET 驱动程序 v3.4 - MongoDB Docs

1、添加MongoDB.Driver

dotnet add package MongoDB.Driver

2、添加MongoDB配置信息到appsettings.json中

"MongoDBConfig": {"BooksCollectionName": "Book","DatabaseName": "BookStoreDB","ConnectionString": "mongodb://localhost:27017/",
}

3、创建MongoDB配置信息类

public class MongoDBConfig
{public string BookCollectionName { get; set; } = string.Empty;public string DatabaseName { get; set; } = string.Empty;public string ConnectionString { get; set; } = string.Empty;
}

4、创建实体类-Book

public class Book
{[BsonId][BsonRepresentation(BsonType.ObjectId)]public string Id { get; set; } = ObjectId.GenerateNewId().ToString();[BsonElement("Name")]public string BookName { get; set; } = string.Empty;public decimal Price { get; set; }public string Category { get; set; } = string.Empty;public string Author { get; set; } = string.Empty;[BsonDateTimeOptions(Kind = DateTimeKind.Local)]public DateTime CreationTime { get; set; } = DateTime.Now;
}

注：[BsonDateTimeOptions(Kind = DateTimeKind.Local)]必须要添加的，因为MongoDB写入时间是协调世界时(UTC)，不加这样注解，查询出来结果会有时区误差。

5、创建自定义MongoDB上下文

public class MongoDBContext
{public IMongoCollection<Book> Books { get; }public MongoDBContext(MongoDBConfig mongodbConfig){if (mongodbConfig != null){if (string.IsNullOrEmpty(mongodbConfig.ConnectionString))throw new ArgumentException("MongoDB connection is not configured");var client = new MongoClient(mongodbConfig.ConnectionString);var database = client.GetDatabase(mongodbConfig.DatabaseName);Books = database.GetCollection<User>(mongodbConfig.BookCollectionName);}else{throw new ArgumentNullException(nameof(mongodbConfig));}}
}

6、创建自定义MongoDB扩展注入服务

public static class MongoDBServiceExtensions
{public static IServiceCollection AddMongoDB(this IServiceCollection services, IConfiguration configuration){services.Configure<MongoDBConfig>(configuration.GetSection("MongoDBConfig"));services.AddSingleton<MongoDBContext>(provider =>{var settings = configuration.GetSection("MongoDBConfig").Get<MongoDBConfig>();return settings == null? throw new InvalidOperationException("MongoDBConfig is not configured properly."): new MongoDBContext(settings);});return services;}
}

注：这里为什么会将MongoDBContext注册为单例服务，因为官方文档推荐单例模式

7、Program.cs文件中注入MongoDB

builder.Services.AddMongoDB(builder.Configuration);

8、使用MongoDB

[ApiController]
[Route("api/[controller]")]public class BookController : ControllerBase
{private readonly ILogger<BookController> _logger;private readonly MongoDBContext _mongodbContext;public BookController(MongoDBContext mongodbContext, ILogger<BookController> logger){_logger = logger;_mongodbContext = mongodbContext;}[HttpGet]public async Task<List<Book>> GetList(){return await _mongodbContext.Books.Find(_ => true).ToListAsync();}[HttpGet("{id:length(24)}")]public async Task<ActionResult<Book>> Get(string id){var book = await _mongodbContext.Books.Find(x => x.Id == id).FirstOrDefaultAsync();if (book is null){return NotFound();}return book;}[HttpPost]public async Task<IActionResult> Post(Book newBook){await _mongodbContext.Books.InsertOneAsync(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 _mongodbContext.Books.Find(x => x.Id == id).FirstOrDefaultAsync();if (book is null){return NotFound();}updatedBook.Id = book.Id;await _mongodbContext.Books.ReplaceOneAsync(x => x.Id == id, updatedBook); ;return NoContent();}[HttpDelete("{id:length(24)}")]public async Task<IActionResult> Delete(string id){var book = await _mongodbContext.Books.Find(x => x.Id == id).FirstOrDefaultAsync();if (book is null){return NotFound();}await _mongodbContext.Books.DeleteOneAsync(x => x.Id == id);return NoContent();}
}