Build a C# application

The following tutorial implements a REST API server using the Entity Framework ORM. The scenario is that of an e-commerce application where database access is managed using the Entity Framework Core. It includes the following tables:

  • users — the users of the e-commerce site
  • products — the products being sold
  • orders — the orders placed by the users
  • orderline — each line item of an order

The source for the above application can be found in the Using ORMs with YugabyteDB repository.

Prerequisites

The tutorial assumes that you have:

  • YugabyteDB up and running. If you are new to YugabyteDB, follow the steps in Quick start to have YugabyteDB up and running in minutes.

  • .NET SDK 6.0 or later.

Clone the "orm-examples" repository

$ git clone https://github.com/yugabyte/orm-examples.git && cd orm-examples/csharp/entityframework

Database configuration

  • To modify the database connection settings, change the default ConnectionStrings in appsettings.json file which is in the following format:

Host=$hostName; Port=$dbPort; Username=$dbUser; Password=$dbPassword; Database=$database

Properties Description Default
Host Database server IP address or DNS name. 127.0.0.1
Port Database port where it accepts client connections. 5433
Username The username to connect to the database. yugabyte
Password The password to connect to the database. yugabyte
Database Database instance in database server. ysql_entityframework

Start the REST API server

To change default port for REST API Server, go to Properties/launchSettings.json and change the applicationUrl field.

  • Build the REST API server.
$ dotnet build
  • Run the REST API server
$ dotnet run

The REST server will run at http://localhost:8080 by default.

Send requests to the application

Create 2 users.

$ curl --data '{ "firstName" : "John", "lastName" : "Smith", "email" : "jsmith@example.com" }' \
   -v -X POST -H 'Content-Type:application/json' http://localhost:8080/users

$ curl --data '{ "firstName" : "Tom", "lastName" : "Stewart", "email" : "tstewart@example.com" }' \
   -v -X POST -H 'Content-Type:application/json' http://localhost:8080/users

Create 2 products.

$ curl \
  --data '{ "productName": "Notebook", "description": "200 page notebook", "price": 7.50 }' \
  -v -X POST -H 'Content-Type:application/json' http://localhost:8080/products

$ curl \
  --data '{ "productName": "Pencil", "description": "Mechanical pencil", "price": 2.50 }' \
  -v -X POST -H 'Content-Type:application/json' http://localhost:8080/products

Verify the userId and productId from the database using the following YSQL commands.

yugabyte=# \c ysql_entityframework

You are now connected to database "ysql_entityframework" as user "yugabyte".

ysql_entityframework=# SELECT count(*) FROM users;

 user_id | first_name | last_name |      user_email
---------+------------+-----------+----------------------
       1 | John       | Smith     | jsmith@example.com
     101 | Tom        | Stewart   | tstewart@example.com
(2 rows)

ysql_entityframework=# SELECT count(*) FROM products;

 product_id |    description    | price | product_name
------------+-------------------+-------+--------------
          1 | 200 page notebook |  7.50 | Notebook
        101 | Mechanical pencil |  2.50 | Pencil
(2 rows)

Create 2 orders with products using the userId for John.

$ curl \
  --data '{ "userId": "1", "products": [ { "productId": 1, "units": 2 } ] }' \
  -v -X POST -H 'Content-Type:application/json' http://localhost:8080/orders

$ curl \
  --data '{ "userId": "1", "products": [ { "productId": 1, "units": 2 }, { "productId": 101, "units": 4 } ] }' \
  -v -X POST -H 'Content-Type:application/json' http://localhost:8080/orders

Query results

Using the YSQL shell

ysql_entityframework=# SELECT count(*) FROM users;

 count
-------
     2
(1 row)

ysql_entityframework=# SELECT count(*) FROM products;

 count
-------
     2
(1 row)

ysql_entityframework=# SELECT count(*) FROM orders;

 count
-------
     2
(1 row)

Using the REST API

To use the REST API server to verify that the users, products, and orders were created in the ysql_entityframework database, enter the following commands. The results are output in JSON format.

$ curl http://localhost:8080/users

{
  "content": [
    {
      "userId": 101,
      "firstName": "Tom",
      "lastName": "Stewart",
      "email": "tstewart@example.com"
    },
    {
      "userId": 1,
      "firstName": "John",
      "lastName": "Smith",
      "email": "jsmith@example.com"
    }
  ],
  ...
}

$ curl http://localhost:8080/products

{
  "content": [
    {
      "productId": 101,
      "productName": "Pencil",
      "description": "Mechanical pencil",
      "price": 2.5
    },
    {
      "productId": 1,
      "productName": "Notebook",
      "description": "200 page notebook",
      "price": 7.5
    }
  ],
  ...
}

$ curl http://localhost:8080/orders

{
  "content": [
    {
      "orderId":"2692e1e9-0bbd-40e8-bf51-4fbcc4e9fea2",
      "orderTime":"2022-02-24T02:32:52.60555",
      "orderTotal":15.00,
      "userId":1,
      "users":null,
      "products":null
    },
    {
      "orderId":"f7343f22-7dfc-4a18-b4d3-9fcd17161518",
      "orderTime":"2022-02-24T02:33:06.832663",
      "orderTotal":25.00,
      "userId":1,
      "users":null,
      "products":null
    }
  ]
}

Explore the source

The application source is available in the orm-examples repository.