Create a web API with ASP.NET Core and MongoDB

By Pratik Khandelwal and Scott Addie

This tutorial creates a web API that runs Create, Read, Update, and Delete (CRUD) operations on a MongoDB NoSQL database.

In this tutorial, you learn how to:

• Configure MongoDB
• Create a MongoDB database
• Define a MongoDB collection and schema
• Perform MongoDB CRUD operations from a web API
• Customize JSON serialization

Prerequisites

• MongoDB 6.0.5 or later
• MongoDB Shell

Visual Studio

• Visual Studio 2022 with the ASP.NET and web development workload.

  

Visual Studio Code

• Visual Studio Code
• C# for Visual Studio Code (latest version)
• .NET 8.0 SDK

The Visual Studio Code instructions use the .NET CLI for ASP.NET Core development functions such as project creation. You can follow these instructions on macOS, Linux, or Windows and with any code editor. Minor changes may be required if you use something other than Visual Studio Code.

Visual Studio for Mac

• Visual Studio 2022 for Mac (latest version)

  Important

  Microsoft has announced the retirement of Visual Studio for Mac. Visual Studio for Mac will no longer be supported starting August 31, 2024. Alternatives include:

  • Visual Studio Code with the C# Dev Kit and related extensions, such as .NET MAUI and Unity.
  • Visual Studio IDE running on Windows in a VM on Mac.
  • Visual Studio IDE running on Windows in a VM in the Cloud.

  For more information, see Visual Studio for Mac retirement announcement.

Configure MongoDB

Enable MongoDB and MongoDB Shell access from anywhere on the development machine (Windows/Linux/macOS):

1. Download and Install MongoDB Shell:

   • macOS/Linux: Choose a directory to extract the MongoDB Shell to. Add the resulting path for mongosh to the PATH environment variable.
   • Windows: MongoDB Shell (mongosh.exe) is installed at C:\Users<user>\AppData\Local\Programs\mongosh. Add the resulting path for mongosh.exe to the PATH environment variable.

2. Download and Install MongoDB:

   • macOS/Linux: Verify the directory that MongoDB was installed at, usually in /usr/local/mongodb. Add the resulting path for mongodb to the PATH environment variable.
   • Windows: MongoDB is installed at C:\Program Files\MongoDB by default. Add C:\Program Files\MongoDB\Server\<version_number>\bin to the PATH environment variable.

3. Choose a Data Storage Directory: Select a directory on your development machine for storing data. Create the directory if it doesn't exist. The MongoDB Shell doesn't create new directories:

   • macOS/Linux: For example, /usr/local/var/mongodb.
   • Windows: For example, C:\\BooksData.

4. In the OS command shell (not the MongoDB Shell), use the following command to connect to MongoDB on default port 27017. Replace <data_directory_path> with the directory chosen in the previous step.

   mongod --dbpath <data_directory_path>
   

Use the previously installed MongoDB Shell in the following steps to create a database, make collections, and store documents. For more information on MongoDB Shell commands, see mongosh.

1. Open a MongoDB command shell instance by launching mongosh.exe.

2. In the command shell, connect to the default test database by running the following command:

   mongosh
   

3. Run the following command in the command shell:

   use BookStore
   

   A database named BookStore is created if it doesn't already exist. If the database does exist, its connection is opened for transactions.

4. Create a Books collection using following command:

   db.createCollection('Books')
   

   The following result is displayed:

   { "ok" : 1 }
   

5. Define a schema for the Books collection and insert two documents using the following command:

   db.Books.insertMany([{ "Name": "Design Patterns", "Price": 54.93, "Category": "Computers", "Author": "Ralph Johnson" }, { "Name": "Clean Code", "Price": 43.15, "Category": "Computers","Author": "Robert C. Martin" }])
   

   A result similar to the following is displayed:

   {
       "acknowledged" : true,
       "insertedIds" : [
           ObjectId("61a6058e6c43f32854e51f51"),
           ObjectId("61a6058e6c43f32854e51f52")
        ]
    }
   

   Note

   The ObjectIds shown in the preceding result won't match those shown in the command shell.

6. View the documents in the database using the following command:

   db.Books.find().pretty()
   

   A result similar to the following is displayed:

   {
        "_id" : ObjectId("61a6058e6c43f32854e51f51"),
        "Name" : "Design Patterns",
        "Price" : 54.93,
        "Category" : "Computers",
        "Author" : "Ralph Johnson"
    }
    {
        "_id" : ObjectId("61a6058e6c43f32854e51f52"),
        "Name" : "Clean Code",
        "Price" : 43.15,
        "Category" : "Computers",
        "Author" : "Robert C. Martin"
    }
   

   The schema adds an autogenerated _id property of type ObjectId for each document.

Create the ASP.NET Core web API project

Visual Studio

1. Go to File > New > Project.

2. Select the ASP.NET Core Web API project type, and select Next.

3. Name the project BookStoreApi, and select Next.

4. Select the .NET 8.0 (Long Term support) framework and select Create.

5. In the Package Manager Console window, navigate to the project root. Run the following command to install the .NET driver for MongoDB:

   Install-Package MongoDB.Driver
   

Visual Studio Code

1. Run the following commands in a command shell:

   dotnet new webapi -o BookStoreApi
   code BookStoreApi
   

   The preceding commands generate a new ASP.NET Core web API project and then open the project in Visual Studio Code.

2. Once the OmniSharp server starts up, a dialog asks Required assets to build and debug are missing from 'BookStoreApi'. Add them?. Select Yes.

3. Open the Integrated Terminal and run the following command to install the .NET driver for MongoDB:

   dotnet add package MongoDB.Driver
   

Visual Studio for Mac

1. Select File > New Project....
2. Select Web and Console > App from the sidebar.
3. Select the ASP.NET Core > API C# project template, and select Next.
4. Select .NET 8.0 from the Target Framework drop-down list, and select Next.
5. Enter BookStoreApi for the Project Name, and select Create.
6. In the Solution pad, right-click the project's Dependencies node and select Manage NuGet Packages.
7. Enter MongoDB.Driver in the search box, select the MongoDB.Driver package, and select Add Package.
8. Select the Accept button in the License Acceptance dialog.

Add an entity model

1. Add a Models directory to the project root.

2. Add a Book class to the Models directory with the following code:

   using MongoDB.Bson;
   using MongoDB.Bson.Serialization.Attributes;
   
   namespace BookStoreApi.Models;
   
   public class Book
   {
       [BsonId]
       [BsonRepresentation(BsonType.ObjectId)]
       public string? Id { get; set; }
   
       [BsonElement("Name")]
       public string BookName { get; set; } = null!;
   
       public decimal Price { get; set; }
   
       public string Category { get; set; } = null!;
   
       public string Author { get; set; } = null!;
   }
   

   In the preceding class, the Id property is:

   • Required for mapping the Common Language Runtime (CLR) object to the MongoDB collection.
   • Annotated with [BsonId] to make this property the document's primary key.
   • Annotated with [BsonRepresentation(BsonType.ObjectId)] to allow passing the parameter as type string instead of an ObjectId structure. Mongo handles the conversion from string to ObjectId.

   The BookName property is annotated with the [BsonElement] attribute. The attribute's value of Name represents the property name in the MongoDB collection.

Add a configuration model

1. Add the following database configuration values to appsettings.json:

   {
       "BookStoreDatabase": {
           "ConnectionString": "mongodb://localhost:27017",
           "DatabaseName": "BookStore",
           "BooksCollectionName": "Books"
       },
       "Logging": {
           "LogLevel": {
               "Default": "Information",
               "Microsoft.AspNetCore": "Warning"
           }
       },
       "AllowedHosts": "*"
   }
   

2. Add a BookStoreDatabaseSettings class to the Models directory with the following code:

   namespace BookStoreApi.Models;
   
   public class BookStoreDatabaseSettings
   {
       public string ConnectionString { get; set; } = null!;
   
       public string DatabaseName { get; set; } = null!;
   
       public string BooksCollectionName { get; set; } = null!;
   }
   

   The preceding BookStoreDatabaseSettings class is used to store the appsettings.json file's BookStoreDatabase property values. The JSON and C# property names are named identically to ease the mapping process.

3. Add the following highlighted code to Program.cs:

   var builder = WebApplication.CreateBuilder(args);
   
   // Add services to the container.
   builder.Services.Configure<BookStoreDatabaseSettings>(
       builder.Configuration.GetSection("BookStoreDatabase"));
   

   In the preceding code, the configuration instance to which the appsettings.json file's BookStoreDatabase section binds is registered in the Dependency Injection (DI) container. For example, the BookStoreDatabaseSettings object's ConnectionString property is populated with the BookStoreDatabase:ConnectionString property in appsettings.json.

4. Add the following code to the top of Program.cs to resolve the BookStoreDatabaseSettings reference:

   using BookStoreApi.Models;
   

Add a CRUD operations service

1. Add a Services directory to the project root.

2. Add a BooksService class to the Services directory with the following code:

   using BookStoreApi.Models;
   using Microsoft.Extensions.Options;
   using MongoDB.Driver;
   
   namespace BookStoreApi.Services;
   
   public class BooksService
   {
       private readonly IMongoCollection<Book> _booksCollection;
   
       public BooksService(
           IOptions<BookStoreDatabaseSettings> bookStoreDatabaseSettings)
       {
           var mongoClient = new MongoClient(
               bookStoreDatabaseSettings.Value.ConnectionString);
   
           var mongoDatabase = mongoClient.GetDatabase(
               bookStoreDatabaseSettings.Value.DatabaseName);
   
           _booksCollection = mongoDatabase.GetCollection<Book>(
               bookStoreDatabaseSettings.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);
   }
   

   In the preceding code, a BookStoreDatabaseSettings instance is retrieved from DI via constructor injection. This technique provides access to the appsettings.json configuration values that were added in the Add a configuration model section.

3. Add the following highlighted code to Program.cs:

   var builder = WebApplication.CreateBuilder(args);
   
   // Add services to the container.
   builder.Services.Configure<BookStoreDatabaseSettings>(
       builder.Configuration.GetSection("BookStoreDatabase"));
   
   builder.Services.AddSingleton<BooksService>();
   

   In the preceding code, the BooksService class is registered with DI to support constructor injection in consuming classes. The singleton service lifetime is most appropriate because BooksService takes a direct dependency on MongoClient. Per the official Mongo Client reuse guidelines, MongoClient should be registered in DI with a singleton service lifetime.

4. Add the following code to the top of Program.cs to resolve the BooksService reference:

   using BookStoreApi.Services;
   

The BooksService class uses the following MongoDB.Driver members to run CRUD operations against the database:

• MongoClient: Reads the server instance for running database operations. The constructor of this class is provided in the MongoDB connection string:

  public BooksService(
      IOptions<BookStoreDatabaseSettings> bookStoreDatabaseSettings)
  {
      var mongoClient = new MongoClient(
          bookStoreDatabaseSettings.Value.ConnectionString);
  
      var mongoDatabase = mongoClient.GetDatabase(
          bookStoreDatabaseSettings.Value.DatabaseName);
  
      _booksCollection = mongoDatabase.GetCollection<Book>(
          bookStoreDatabaseSettings.Value.BooksCollectionName);
  }
  

• IMongoDatabase: Represents the Mongo database for running operations. This tutorial uses the generic GetCollection<TDocument>(collection) method on the interface to gain access to data in a specific collection. Run CRUD operations against the collection after this method is called. In the GetCollection<TDocument>(collection) method call:

  • collection represents the collection name.
  • TDocument represents the CLR object type stored in the collection.

GetCollection<TDocument>(collection) returns a MongoCollection object representing the collection. In this tutorial, the following methods are invoked on the collection:

• DeleteOneAsync: Deletes a single document matching the provided search criteria.
• Find<TDocument>: Returns all documents in the collection matching the provided search criteria.
• InsertOneAsync: Inserts the provided object as a new document in the collection.
• ReplaceOneAsync: Replaces the single document matching the provided search criteria with the provided object.

Add a controller

Add a BooksController class to the Controllers directory with the following code:

using BookStoreApi.Models;
using BookStoreApi.Services;
using Microsoft.AspNetCore.Mvc;

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();
    }
}

The preceding web API controller:

• Uses the BooksService class to run CRUD operations.
• Contains action methods to support GET, POST, PUT, and DELETE HTTP requests.
• Calls CreatedAtAction in the Create action method to return an HTTP 201 response. Status code 201 is the standard response for an HTTP POST method that creates a new resource on the server. CreatedAtAction also adds a Location header to the response. The Location header specifies the URI of the newly created book.

Test the web API

1. Build and run the app.

2. Navigate to https://localhost:<port>/api/books, where <port> is the automatically assigned port number for the app, to test the controller's parameterless Get action method, select Try it out > Execute. A JSON response similar to the following is displayed:

   [
     {
       "id": "61a6058e6c43f32854e51f51",
       "bookName": "Design Patterns",
       "price": 54.93,
       "category": "Computers",
       "author": "Ralph Johnson"
     },
     {
       "id": "61a6058e6c43f32854e51f52",
       "bookName": "Clean Code",
       "price": 43.15,
       "category": "Computers",
       "author": "Robert C. Martin"
     }
   ]
   

3. Navigate to https://localhost:<port>/api/books/{id here} to test the controller's overloaded Get action method. A JSON response similar to the following is displayed:

   {
     "id": "61a6058e6c43f32854e51f52",
     "bookName": "Clean Code",
     "price": 43.15,
     "category": "Computers",
     "author": "Robert C. Martin"
   }
   

Configure JSON serialization options

There are two details to change about the JSON responses returned in the Test the web API section:

• The property names' default camel casing should be changed to match the Pascal casing of the CLR object's property names.
• The bookName property should be returned as Name.

To satisfy the preceding requirements, make the following changes:

1. In Program.cs, chain the following highlighted code on to the AddControllers method call:

   var builder = WebApplication.CreateBuilder(args);
   
   // Add services to the container.
   builder.Services.Configure<BookStoreDatabaseSettings>(
       builder.Configuration.GetSection("BookStoreDatabase"));
   
   builder.Services.AddSingleton<BooksService>();
   
   builder.Services.AddControllers()
       .AddJsonOptions(
           options => options.JsonSerializerOptions.PropertyNamingPolicy = null);
   

   With the preceding change, property names in the web API's serialized JSON response match their corresponding property names in the CLR object type. For example, the Book class's Author property serializes as Author instead of author.

2. In Models/Book.cs, annotate the BookName property with the [JsonPropertyName] attribute:

   [BsonElement("Name")]
   [JsonPropertyName("Name")]
   public string BookName { get; set; } = null!;
   

   The [JsonPropertyName] attribute's value of Name represents the property name in the web API's serialized JSON response.

3. Add the following code to the top of Models/Book.cs to resolve the [JsonProperty] attribute reference:

   using System.Text.Json.Serialization;
   

4. Repeat the steps defined in the Test the web API section. Notice the difference in JSON property names.

Add authentication support to a web API

ASP.NET Core Identity adds user interface (UI) login functionality to ASP.NET Core web apps. To secure web APIs and SPAs, use one of the following:

• Microsoft Entra ID
• Azure Active Directory B2C (Azure AD B2C)
• Duende Identity Server

Duende Identity Server is an OpenID Connect and OAuth 2.0 framework for ASP.NET Core. Duende Identity Server enables the following security features:

• Authentication as a Service (AaaS)
• Single sign-on/off (SSO) over multiple application types
• Access control for APIs
• Federation Gateway

Important

Duende Software might require you to pay a license fee for production use of Duende Identity Server. For more information, see Migrate from ASP.NET Core 5.0 to 6.0.

For more information, see the Duende Identity Server documentation (Duende Software website).

Additional resources

• View or download sample code (how to download)
• Create web APIs with ASP.NET Core
• Controller action return types in ASP.NET Core web API
• Create a web API with ASP.NET Core