Create a web API with ASP.NET Core and MongoDB

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By Pratik Khandelwal and Scott Addie

:::moniker range=">= aspnetcore-9.0"

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:

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• 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

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Visual Studio Code

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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.

   consoleCopy

   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, or by running the following command in the command shell:

   consoleCopy

   mongosh
   

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

   consoleCopy

   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.

3. Create a Books collection using following command:

   consoleCopy

   db.createCollection('Books')
   

   The following result is displayed:

   consoleCopy

   { "ok" : 1 }
   

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

   consoleCopy

   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:

   consoleCopy

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

   [!NOTE] The ObjectIds shown in the preceding result won't match those shown in the command shell.

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

   consoleCopy

   db.Books.find().pretty()
   

   A result similar to the following is displayed:

   consoleCopy

   {
        "_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. In the Additional information dialog:

• Confirm the Framework is .NET 9.0 (Standard Term Support).
• Confirm the checkbox for Use controllers is checked.
• Confirm the checkbox for Enable OpenAPI support is checked.
• Select Create.

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

   powershellCopy

   Install-Package MongoDB.Driver
   

Visual Studio Code

1. Run the following commands in a command shell:

   dotnetcliCopy

   dotnet new webapi -o BookStoreApi --use-controllers
   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:

   dotnetcliCopy

   dotnet add package MongoDB.Driver
   

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:

   :::code language="csharp" source="first-mongo-app/samples_snapshot/9.x/Book.cs":::

   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:

   :::code language="json" source="first-mongo-app/samples/9.x/BookStoreApi/appsettings.json" highlight="2-6":::

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

   :::code language="csharp" source="first-mongo-app/samples/9.x/BookStoreApi/Models/BookStoreDatabaseSettings.cs":::

   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:

   :::code language="csharp" source="first-mongo-app/samples/9.x/BookStoreApi/Program.cs" id="snippet_BookStoreDatabaseSettings" highlight="4-5":::

   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:

   :::code language="csharp" source="first-mongo-app/samples/9.x/BookStoreApi/Program.cs" id="snippet_UsingModels":::

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:

   :::code language="csharp" source="first-mongo-app/samples/9.x/BookStoreApi/Services/BooksService.cs" id="snippet_File":::

   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:

   :::code language="csharp" source="first-mongo-app/samples/9.x/BookStoreApi/Program.cs" id="snippet_BooksService" highlight="7":::

   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:

   :::code language="csharp" source="first-mongo-app/samples/9.x/BookStoreApi/Program.cs" id="snippet_UsingServices":::

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:

  :::code language="csharp" source="first-mongo-app/samples/9.x/BookStoreApi/Services/BooksService.cs" id="snippet_ctor" highlight="4-5":::

• 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:

:::code language="csharp" source="first-mongo-app/samples/9.x/BookStoreApi/Controllers/BooksController.cs":::

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 xref:Microsoft.AspNetCore.Mvc.ControllerBase.CreatedAtAction%2A 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.

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:

   :::code language="csharp" source="first-mongo-app/samples/9.x/BookStoreApi/Program.cs" id="snippet_AddControllers" highlight="10-11":::

   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:

   :::code language="csharp" source="first-mongo-app/samples/9.x/BookStoreApi/Models/Book.cs" id="snippet_BookName" highlight="2":::

   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:

   :::code language="csharp" source="first-mongo-app/samples/9.x/BookStoreApi/Models/Book.cs" id="snippet_UsingSystemTextJsonSerialization":::

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

Test the web API

Visual Studio

This tutorial uses Endpoints Explorer and .http files to test the API.

1. Build and run the app.

2. In Endpoints Explorer, right-click the first GET endpoint /api/books, and select Generate request.

   The following content is added to the BookStoreApi.http file. If this is the first time that a request is generated, the file is created in the project root.

   Copy

   @BookStoreApi_HostAddress = https://localhost:<port>
    
   GET {{BookStoreApi_HostAddress}}/api/books
    
   ###
   

   The port number should already be set to the port used by the app, for example, https://localhost:56874. If that's not the case you can find your port number in the output window when you launch the app.

3. Select the Send request link above the new GET request line.

   The GET request is sent to the app and the response is displayed in the Response pane.

4. The response body shows the JSON result containing the book entries similar to the following:

   jsonCopy

   [
     {
       "Id": "61a6058e6c43f32854e51f51",
       "Name": "Design Patterns",
       "Price": 54.93,
       "Category": "Computers",
       "Author": "Ralph Johnson"
     },
     {
       "Id": "61a6058e6c43f32854e51f52",
       "Name": "Clean Code",
       "Price": 43.15,
       "Category": "Computers",
       "Author": "Robert C. Martin"
     }
   ]
   

5. To retrieve a single book, right-click the /api/books/{id}, params (string id) GET endpoint in the Endpoints Explorer, and select Generate request.

   The following content is appended to the BookStoreApi.http file:

   Copy

   @id=string
   GET {{BookStoreApi_HostAddress}}/api/books/{{id}}
   
   ###
   

6. Replace id variable with one of the IDs returned from the earlier request, for example:

   Copy

   @id="61a6058e6c43f32854e51f52"
   GET {{BookStoreApi_HostAddress}}/api/books/{{id}}
   
   ###
   

7. Select the Send request link above the new GET request line.

   The GET request is sent to the app and the response is displayed in the Response pane.

8. The response body shows JSON similar to the following:

   jsonCopy

   {
     "Id": "61a6058e6c43f32854e51f52",
     "Name": "Clean Code",
     "Price": 43.15,
     "Category": "Computers",
     "Author": "Robert C. Martin"
   }
   

9. To test the POST endpoint, right-click the /api/books POST endpoint and select Generate request.

   The following content is added to the BookStoreApi.http file:

   Copy

   POST {{BookStoreApi_HostAddress}}/api/books
   Content-Type: application/json
   
   {
     //Book
   }
   
   ###
   

10. Replace the Book comment with a book object as the JSON request body:

    Copy

    POST {{BookStoreApi_HostAddress}}/api/books
    Content-Type: application/json
    
     {
       "Name": "The Pragmatic Programmer",
       "Price": 49.99,
       "Category": "Computers",
       "Author": "Andy Hunt"
     }
    
    ###
    

11. Select the Send request link above the POST request line.

    The POST request is sent to the app, and the response is displayed in the Response pane. The response should include the newly created book with its assigned ID.

12. Lastly, to delete a book, right-click the /api/books/{id}, params (string id) DELETE endpoint and select Generate request.

    The following content is appended to the BookStoreApi.http file:

    Copy

    DELETE {{BookStoreApi_HostAddress}}/api/Books/{{id}}
     
    ###
    

13. Replace the id variable with one of the IDs returned from the earlier request, and click Send request. For example:

    Copy

    DELETE {{BookStoreApi_HostAddress}}/api/Books/67f417517ce1b36aeab71236
    
    ###
    

Visual Studio Code

This tutorial uses the OpenAPI specification (openapi.json) and Swagger UI to test the API.

1. Install Swagger UI by running the following command:

dotnet add package NSwag.AspNetCore

The previous command adds the NSwag.AspNetCore package, which contains tools to generate Swagger documents and UI. Because our project is using OpenAPI, we only use the NSwag package to generate the Swagger UI.

1. Configure Swagger middleware

In Program.cs, add the following highlighted code:

:::code language="csharp" source="first-mongo-app/samples/9.x/BookStoreApi/Program.cs" id="snippet_UseSwagger" highlight="6-9":::

The previous code enables the Swagger middleware for serving the generated JSON document using the Swagger UI. Swagger is only enabled in a development environment. Enabling Swagger in a production environment could expose potentially sensitive details about the API's structure and implementation.

The app uses the OpenAPI document generated by OpenApi, located at /openapi/v1.json, to generate the UI. View the generated OpenAPI specification for the WeatherForecast API while the project is running by navigating to https://localhost:<port>/openapi/v1.json in your browser.

The OpenAPI specification is a document in JSON format that describes the structure and capabilities of your API, including endpoints, request/response formats, parameters, and more. It's essentially a blueprint of your API that can be used by various tools to understand and interact with your API.

1. Build and run the app.

2. Navigate to https://localhost:<port>/swagger in your browser. Swagger provides a UI to test all the API endpoints based on the OpenAPI document.

3. Expand the GET /api/books endpoint and click the Try it out button.

4. Click the Execute button to send the request to the API.

5. The Response body section displays a JSON array with books similar to the following:

   jsonCopy

   [
     {
       "Id": "61a6058e6c43f32854e51f51",
       "Name": "Design Patterns",
       "Price": 54.93,
       "Category": "Computers",
       "Author": "Ralph Johnson"
     },
     {
       "Id": "61a6058e6c43f32854e51f52",
       "Name": "Clean Code",
       "Price": 43.15,
       "Category": "Computers",
       "Author": "Robert C. Martin"
     }
   ]
   

6. Next, expand the GET /api/books/{id} endpoint and click Try it out.

7. Enter one of the book IDs from the previous response in the id field, then click Execute.

8. The Response body section displays the JSON object for the specified book. For example, the result for the ID 61a6058e6c43f32854e51f52 is similar to the following:

   jsonCopy

   {
     "Id": "61a6058e6c43f32854e51f52",
     "Name": "Clean Code",
     "Price": 43.15,
     "Category": "Computers",
     "Author": "Robert C. Martin"
   }
   

9. To test creating a new book, expand the POST /api/books endpoint and click Try it out.

10. Replace the default request body with a new book object:

    jsonCopy

    {
      "Name": "The Pragmatic Programmer",
      "Price": 49.99,
      "Category": "Computers",
      "Author": "Andy Hunt"
    }
    

11. Click Execute to send the request.

12. The response should have a status code of 201 (Created) and include the newly created book with its assigned ID in the response body.

13. Lastly, to delete a book record, expand the DELETE /api/books/{id} endpoint, click Try it out, and enter one of the book IDs from the previous response in the id field. Click Execute to send the request.

14. The response should have a status code of 204 (No Content), indicating that the book was successfully deleted.

Add authentication support to a web API

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Additional resources

• View or download sample code (how to download)
• xref:web-api/index
• xref:web-api/action-return-types
• Create a web API with ASP.NET Core

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