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A Sample On .Net Core Web API Using Dapper


Overview On Dapper Object-Relational Mapping:

Dapper is an Object-Relational Mapping framework for .Net applications. It is a mapping model between the database and .Net objects. The Dapper provides all query and command execution methods as extension methods under the 'System.Data.IDbConnection' interface. The Dapper works as a similar ADO.Net but with much more model mapping support. The Dapper key features are like:
  • High performance in query execution
  • Multiple query execution support
  • An easy model mapping between the .Net Object and database result.

Create A Sample .Net Core Web API Application:

Let's understand the Dapper ORM query and commands execution steps by writing some sample code, so let's get started by creating a .Net Core Web API application. The IDE's for development can be chosen by personal preference but the most recommended IDE's are Visual Studio 2019 and Visual Studio Code.

SQL Table Schema:

In this article we are going to work on 'Todo' table, so execute the below table schema.
CREATE TABLE [dbo].[Todo] (
    [Id]  INT  IDENTITY (1, 1) NOT NULL,
    [ItemName] VARCHAR (MAX) NULL,
    [IsCompleted] BIT NOT NULL
);
Now run the sample test data. 
SET IDENTITY_INSERT [dbo].[Todo] ON
INSERT INTO [dbo].[Todo] ([Id], [ItemName], [IsCompleted]) VALUES (1, N'Buy a book', 1)
INSERT INTO [dbo].[Todo] ([Id], [ItemName], [IsCompleted]) VALUES (2, N'Need To Watch Movie', 0)
INSERT INTO [dbo].[Todo] ([Id], [ItemName], [IsCompleted]) VALUES (3, N'Book A Flight Ticke', 0)
SET IDENTITY_INSERT [dbo].[Todo] OFF

Install Packages:

SQL Provider Package:

Install-Package System.Data.SqlClient
Dapper Package:

Install-Package Dapper

Initial Project Configuration Steps(Connection String / Models / Repositories):

In this section we are going to implement initial steps like adding ConnectionString, Models, Repositories with some basic configurations.

In appsettings.development.json file add your SQL connection string as below.
{
  "Logging": {
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "MyWorldDbConnection": "your_sql_server_connection"
  }
}
Now add Todo.cs model
Models/Todo.cs: 
namespace API.Dapper.Sample.Models
{
    public class Todo
    {
        public int Id { get; set; }
        public string ItemName { get; set; }
        public bool IsCompleted { get; set; }
    }
}
Now let's create 'Todo' repository and it interface.
Repos/ITodoRepository.cs:
using API.Dapper.Sample.Models;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace API.Dapper.Sample.Repos
{
    public interface ITodosRepository
    {
        
    }
}
  • Here we have added few references(libraries accessed with using statement) intentionally because all these references are required by us on completion of the sample.
Repos/TodoRepository.cs: 
using API.Dapper.Sample.Models;
using Dapper;
using Microsoft.Extensions.Configuration;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Threading.Tasks;

namespace API.Dapper.Sample.Repos
{
    public class TodosRepository: ITodosRepository
    {
        private string myWorldDbConnection = string.Empty;

        private IDbConnection Connection
        {
            get
            {
                return new SqlConnection(myWorldDbConnection);
            }
        }
        public TodosRepository(IConfiguration configuration)
        {
            myWorldDbConnection = configuration.GetConnectionString("MyWorldDbConnection");
        }
    }
}
  • (Line: 25) The 'Microsoft.Extensions.Configuration.IConfiguration' is injected into the 'TodosRepository'. The 'IConfiguration' interface has the capability to access the appsettings. The 'GetConnectionString()' is default method in 'IConfiguration' which can read the 'ConnectionStrings' property object in the appsettings.
  • (Line: 16-22) The 'Connection' property of type 'System.Data.IDbConnection' initialized. This property uses 'System.Data.SqlClient.SqlConnection' instance to open the database connection.
Now register the 'TodosRepository' in DI(dependency injection) service in the startup file
Startup.cs:
public void ConfigureServices(IServiceCollection services)
{
	services.AddControllers();
	services.AddScoped<ITodosRepository, TodosRepository>();
}
Let's now add a 'TodosController' as follow
Controllers/TodosController.cs:
using API.Dapper.Sample.Models;
using API.Dapper.Sample.Repos;
using Microsoft.AspNetCore.Mvc;
using System.Threading.Tasks;

namespace API.Dapper.Sample.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class TodosController : ControllerBase
    {
        private readonly ITodosRepository _todosRepository;
        public TodosController(ITodosRepository todosRepository)
        {
            _todosRepository = todosRepository;
        }
    }
}
  • (Line: 13) Injects 'ITodosRepository'

Read Collection Of Records:

Using Dapper ORM query extension methods we need to fetch collection records from the database.

Now create an abstract method in the 'ITodosRepository.cs' that represents a method that outputs the collection of records.
Repos/ITodosRepository.cs:
Task<List<Todo>> GetAllTodosAsync();
Now implement this abstract method in the 'TodosRepository.cs'
Repos/TodosRepository.cs: 
public async Task<List<Todo>> GetAllTodosAsync()
{
	using(IDbConnection conn = Connection)
	{
		string query = "SELECT * FROM Todo";
		List<Todo> todos = (await conn.QueryAsync<Todo>(sql: query)).ToList();
		return todos;
	}
}
  • (Line: 3) The 'using' statement automatically closes the database connection string once the scope of the code executes out the 'using' statement.
  • (Line: 5) The simple raw SQL query to fetch all records.
  • (Line: 6) The 'Dapper.SqlMapper..QueryAsync<T>()' method which we using as extension method of 'System.Data.IDbConnection'. The QueryAsync method executes the query which takes it as an input parameter and returns the data by mapping to the 'T' type defined to it.
Now define the action method endpoint.
Controllers/TodosController.cs:
[HttpGet]
[Route("get-all")]
public async Task<IActionResult> GetAllTodosAsync()
{
	var result = await _todosRepository.GetAllTodosAsync();
	return Ok(result);
}

Read Single Record:

Let's define an abstract method in 'ITodosRepository', this method going to fulfill the role to return a single record from our repository.
Repos/ITodosRepository.cs:
Task<Todo> GetTodoByIdAsync(int id);
Now let's implement this abstract method into our 'TodosRepository'
Repos/TodosRepository.cs: 
public async Task<Todo> GetTodoByIdAsync(int id)
{
	using(IDbConnection conn = Connection)
	{
		string query = "SELECT * FROM Todo WHERE Id = @id";
		Todo todo = await conn.QueryFirstOrDefaultAsync<Todo>(sql: query, param: new { id });
		return todo;
	}
}
  • (Line: 5) Now the raw SQL query contains parameter '@id', dapper will pass the value at the time query execution.
  • (Line: 6) The extension method 'QueryFirstOrDefaultAsync' returns the first record as per the filter we passed. To this extension method, we are passing filter values as anonymous objects using the 'new' keyword.
Now define the action method endpoint
Controllers/TodosController.cs:
[HttpGet]
[Route("get-todoitem-by-id")]
public async Task<IActionResult> GetTodoItemByIdAsync(int id)
{
	var result = await _todosRepository.GetTodoByIdAsync(id);
	return Ok(result);
}

Read Multiple Result Sets:

The Dapper has the capability to return the multiple table results sets. Now let's create a new model to capture multiple results.
Models/TodosContainer.cs:
using System.Collections.Generic;

namespace API.Dapper.Sample.Models
{
    public class TodosContainer
    {
        public int Count { get; set; }
        public List<Todo> Todos {get;set;}
    }
}
  • Here we have 2 properties one for the total count and the other for the list of 'Todos'.
Now let's define an abstract method for reading multiple results in 'ITodosRepository'
Repos/ITodosRepository.cs:
Task<TodosContainer> GetTodosAndCountAsync();
Now let's write an implementation for this abstract method
Repos/TodosRepository.cs:
public async Task<TodosContainer> GetTodosAndCountAsync()
{
	using (IDbConnection conn = Connection)
	{
		string query = @"
				SELECT COUNT(*) FROM Todo

	
				SELECT * FROM Todo";

		var reader = await conn.QueryMultipleAsync(sql: query);

		return new TodosContainer
		{
			Count = (await reader.ReadAsync<int>()).FirstOrDefault(),
			Todos = (await reader.ReadAsync<Todo>()).ToList()
		};
	}
}
  • (Line: 5-9) Here defined to queries one returns count of todos and other returns total todos(If you want you can return select query of fetching data of two tables also).
  • (Line: 11) The extension method 'QueryMultipleAsync' executes the query and returns multiple result sets.
  • (Line: 15) Reading the first result set i.e total count.
  • (Line: 16) Reading the second result set i.e collection of 'Todos'.
Now let's define the action method endpoint.
Controllers/TodosController.cs:
[HttpGet]
[Route("get-todos-and-count")]
public async Task<IActionResult> GetTodosAndCountAsync()
{
	var result = await _todosRepository.GetTodosAndCountAsync();
	return Ok(result);
}

Save Record:

Repos/ITodosRepository.cs:
Task<int> SaveAsync(Todo newTodo);
Repos/TodosRepository.cs: 
public async Task<int> SaveAsync(Todo newTodo)
{
	using(IDbConnection conn = Connection)
	{
		string command = @"
				INSERT INTO Todo(ItemName, IsCompleted)
				VALUES(@ItemName, @IsCompleted)";

		var result = await conn.ExecuteAsync(sql: command, param: newTodo);
		return result;
	}
}
  • (Line: 6-7) Here we can see SQL insert command and with dynamic parameters like '@ItemName','@IsCompleted'.
  • (Line: 9) The extension method 'ExecuteAsync' executes the given command to it. This method takes 'param' as 'newTodo'(Todo instance), each property name of 'newTodo' must match with the dynamic parameter name is the SQL command. The return type of the 'ExecuteAsync' is an integer value to represent the number of rows was effected on command execution, so if it returns zero then there is no effect of the command on the database.
Now let's define the action method endpoint.
Controllers/TodosController.cs:
[HttpPost]
[Route("save")]
public async Task<IActionResult> SaveAsync(Todo newTodo)
{
	var result = await _todosRepository.SaveAsync(newTodo);
	return Ok(result);
}

Update Record:

Repos/ITodosRepository:
Task<int> UpdateTodoStatusAsync(Todo updateTodo);
Repos/TodosRepository: 
public async Task<int> UpdateTodoStatusAsync(Todo updateTodo)
{
	using(IDbConnection conn = Connection)
	{
		string command = @"
		UPDATE Todo SET IsCompleted = @IsCompleted WHERE Id = @Id";

		var result = await conn.ExecuteAsync(sql: command, param: updateTodo);
		return result;
	}
}
  • Here we are updating only the 'IsCompleted' column of the Todo table
Controllers/TodosController.cs: 
[HttpPost]
[Route("update-todo-status")]
public async Task<IActionResult> UpdateTodoStatusAsync(Todo updateTodo)
{
	var result = await _todosRepository.UpdateTodoStatusAsync(updateTodo);
	return Ok(result);
}

Delete Record:

Repos/ITodosRepository:
Task<int> DeleteAsync(int id);
Repos/TodosRepository: 
public async Task<int> DeleteAsync(int id)
{
	using(IDbConnection conn = Connection)
	{
		string command = @"DELETE FROM Todo WHERE Id = @id";
		var result = await conn.ExecuteAsync(sql: command, param: new { id });
		return result;
	}
}
  • Here we can observe SQL raw delete query based on the '@id' parameter
Controllers/TodoController.cs: 
[HttpDelete]
[Route("delete")]
public async Task<IActionResult> DeleteAsync(int id)
{
	var result = await _todosRepository.DeleteAsync(id);
	return Ok(result);
}

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Wrapping Up:

Hopefully, I think this article delivered some useful information on the Dapper ORM integration in .Net Core Application. I love to have your feedback, suggestions, and better techniques in the comment section below.

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