Skip to main content

A Demo On Hot Chocolate GraphQL Integration In Asp.Net Core Application Using Dapper Micro ORM

In this article, we are going to implement a GraphQL Endpoint by using Pure Code First Techniques in the Asp.Net Core application, and database communication will be accomplished by using Dapper Micro ORM.

GraphQL:

GraphQL is an open-source data query and manipulation and language for APIs. It is a query language for your API and a server-side runtime for executing queries by using a type system you define for your data. GraphQL can be integrated into any framework like .Net, Java, NestJS, etc and it isn't tied to any specific database or storage engine and is instead backed by your existing code and data.

GraphQL main operations are:
  • Query (fetching data)
  • Mutation (saving or updating data)

Hot Chocolate GraphQL:

Hot Chocolate is the wrapper library of the original.Net GraphQL library. Hot Chocolate takes the complexity away from building a fully-fledged GraphQL server.

The hot Chocolate library provides 3 different techniques:
  • Schema First
  • Code First
  • Pure Code First
Schema First: This approach fully involves writing GraphQL Schema Definition Language.

Code First: No schema writing, but every plain c# class should have mapping GraphQL c# class.

Pure Code First: No schema writing, no GraphQL c# classes, only plain c# classes are enough. This approach is very simple, schema generation is taken care of by the GraphQL server. Our demo going to adopt this technique to accomplish the GraphQL endpoint.

Create A .Net5 Web API Application:

Let's create a .Net5 Web API application to accomplish our demo.


Dapper:

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.

Install Dapper And Dependent Packages:

Now install the 'Dapper' package.

Now install the 'System.Data.SqlClient' package.

Create A Sample Service Files:

Let's create sample service files like 'PersonService.cs' and 'IPersonService.cs' where we are going to write our database communication logic using the dapper.
Services/IPersonService.cs:
namespace HotChoco.Dapper.Api.Services
{
    public interface IPersonService
    {
    }
}
Services/PersonService.cs:
using Microsoft.Extensions.Configuration;
using System.Data;
using System.Data.SqlClient;

namespace HotChoco.Dapper.Api.Services
{
    public class PersonService: IPersonService
    {
        private readonly IConfiguration _configuration;

        private IDbConnection Connection
        {
            get
            {
                return new SqlConnection(_configuration.GetConnectionString("MyWorldDbConnection"));
            }
        }
        public PersonService(IConfiguration configuration)
        {
            _configuration = configuration;
        }

    }
}
  • (Line: 11-17) Initialize 'SqlConnection' instance.
Now register our service file into the 'Startup.cs'.
Startup.cs:
services.AddScoped<IPersonService, PersonService>();

Install Hot Chocolate GraphQL Library:

Now let's install 'HotChocolate.AspNetCore' package.

Register GraphQL Server And Endpoint:

Now configure the GraphQL server.
Startup.cs:
services.AddGraphQLServer();
Configure the GraphQL endpoint.
Startup.cs:
app.UseEndpoints(endpoints =>
{
	endpoints.MapGraphQL();
	endpoints.MapControllers();
});

Create And Register The Query Resolver File:

Resolver methods are the logical units of the GraphQL endpoints. We have to create individual resolver files for Query and Mutation operations.

Let's create a Query resolver file like 'PersonQueryResolver.cs'.
QueryResolver/PersonQueryResolver.cs:
using HotChocolate.Types;

namespace HotChoco.Dapper.Api.QueryResolver
{
    [ExtendObjectType("Query")]
    public class PersonQueryResolver
    {
    }
}
  • (Line: 5) Our resolver method should be decorated with 'HotChocolate.Types.ExtendObjectType' and we have to pass the name that we have registered globally in the 'Startup.cs'.
Now let's define the Root Query name and also register our resolver type in the 'Startup.cs'
Startup.cs:
services.AddGraphQLServer()
.AddQueryType(q => q.Name("Query"))
.AddType<PersonQueryResolver>();
  • (Line: 2) Register the 'AddQueryType' and define a name like 'Query'. This name should be used by all the query resolvers with the help of 'ExtendObjecType'.
  • (Line: 3) Registered our 'PersonQueryResolver' type.

Query Single Record:

Let's create a response model for our endpoint like 'PersonDto.cs'.
Dtos/PersonDto.cs:
namespace HotChoco.Dapper.Api.Dtos
{
    public class PersonDto
    {
        public int ID { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string Age { get; set; }
    }
}
Using dapper let's write our logic to fetch a single record from the database.
Services/IPersonService.cs:
using HotChoco.Dapper.Api.Dtos;

namespace HotChoco.Dapper.Api.Services
{
    public interface IPersonService
    {
        PersonDto GetFirst();
    }
}
Services/PersonService.cs:
public PersonDto GetFirst()
{

	using (var conn = Connection)
	{
		var query = "Select top 1 * from Persons";
		var person = conn.Query<PersonDto>(query).FirstOrDefault();
		return person;
	}
}
  • (Line: 6) Defined raw SQL query.
  • (Line: 7) The 'Query<T>' extension executes the specified query against the SQL database and results will be automatically typecasted to specified type 'T'.
Now let's create our endpoint method in the resolver file as below.
QueryResolver/PersonQueryResolver.cs:
public PersonDto GetFirstPerson([Service] IPersonService personService)
{
	return personService.GetFirst();
}
  • Methods in the resolver class are the entry points of the GraphQL endpoint.
  • (Line: 1) Injecting our 'IPersonService' using the 'HotChocolate.Service' attribute.
Sample request query looks like below:
query{
  firstPerson{
     firstName
     lastName
     age
  }
}
  • (Line: 1) The 'query' keyword represents GraphQL operation type.
  • (Line: 2) The 'firstPerson' keyword must match with the name of our resolver method but the first character should be small(which means lower camel case).
  • (Line: 3-5) In GraphQL request we can specify payload properties by ourselves only requested will be served by the server. Here also names of the properties should follow the 'Lower Camel Case'.
Now run our application and access the '/graphql' endpoint to check the results.

Query Multiple Records:

Using dapper let's write our logic to fetch a collection of data.
Services/IPersonService.cs:
List<PersonDto> GetAll();
Services/PersonService.cs:
public List<PersonDto> GetAll()
{
	using (var conn = Connection)
	{
		var query = "Select * from Persons";
		var persons = conn.Query<PersonDto>(query).ToList();
		return persons;
	}
}
  • Here fetching collection of 'Persons' records.
Now add our resolver method that returns a collection of data.
QueryResolver/PersonQueryResolver.cs:
public List<PersonDto> GetAllPerson([Service] IPersonService personService)
{
	return personService.GetAll();
}
Sample request query looks like below:
query{
  allPerson{
    firstName
    age
  }
}

Query With Filter Parameters:

Using dapper let's add logic to filter the data by 'FirstName' from the database.
Services/IPersonService.cs:
List<PersonDto> FilterByFirstName(string firstName);
Services/PersonService.cs:
public List<PersonDto> FilterByFirstName(string firstName)
{
	using(var conn = Connection)
	{
		var query = "Select * from Persons where FirstName = @firstName";
		var persons = conn.Query<PersonDto>(query, new { firstName }).ToList();
		return persons;
	}
}
Let's add a resolver method with a filter parameter.
QueryResolver/PersonQueryResolver.cs:
public List<PersonDto> FilterByFirstName(string firstName, [Service] IPersonService personService)
{
	return personService.FilterByFirstName(firstName);
}
Sample Query with query parameter as below:
query($searchByFirstName:String){
  filterByFirstName(firstName:$searchByFirstName){
    firstName
  }
}
  • Here '$searchByFirstName' is the GraphQL variable name.
GraphQL Variable as below:
{
  "searchByFirstName": "naveen"
}

Query Complex Object Types:

Let's understand how to fetch the data for complex object types (parent and child-related objects).
Let's create child object class like 'PersonAddressDto.cs'.
Dtos/PersonAddressDto.cs:
namespace HotChoco.Dapper.Api.Dtos
{
    public class PersonAddressDto
    {
        public int PersonAddressId { get; set; }
        public string AddressLine1 { get; set; }
        public string AddressLine2 { get; set; }
        public string City { get; set; }
        public string State { get; set; }
        public string Country { get; set; }
        public int PersonId { get; set; }
    }
}
Now update the 'PersonDto' with a navigation peroperty of type 'PersonAddressDot'.
Dtos/PersonDto.cs:
using System.Collections.Generic;

namespace HotChoco.Dapper.Api.Dtos
{
    public class PersonDto
    {
        public int ID { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string Age { get; set; }
        public List<PersonAddressDto> Address { get; set; }
    }
}
Using dapper let's write logic to fetch multiple result sets from the database.
Services/IPersonService.cs:
List<PersonDto> GetPersonAddress();
Services/PersonService.cs:
public List<PersonDto> GetPersonAddress()
{
	using (var conn = Connection)
	{
		var query = @"
					Select * From Persons

					Select * From PersonAddress
					";

		var result = conn.QueryMultiple(query);
		var persons = result.Read<PersonDto>().ToList();
		var address = result.Read<PersonAddressDto>().ToList();
		foreach (var person in persons)
		{
			person.Address = address.Where(_ => _.PersonId == person.ID).ToList();
		}
		return persons;
	}
}
  • Here we are fetching 2 result sets like 'Persons' and 'PersonAddres' using the dapper 'QueryMultiple' method.
Let's implement our resolver method as below:
QueryResolver/PersonQueryResolver.cs:
public List<PersonDto> GetPersonAddress([Service] IPersonService personService)
{
	return personService.GetPersonAddress();
}
Sample Query looks like below:
query{
  personAddress{
    lastName
    address{
      addressLine1
      addressLine1
      city
      state
      country
    }
  }
}
  • (Line: 4-10) specifying required properties of the child object(address object). In this way, we can fetch the child object properties in a relational object response.

Create And Register Mutation Resolver File:

Let's create the Mutation resolver file like 'PersonMutationResolver.cs'.
MutationResolver/PersonMutationResolver.cs:
using HotChocolate.Types;

namespace HotChoco.Dapper.Api.MutationResolver
{
    [ExtendObjectType("Mutation")]
    public class PersonMutationResolver
    {
    }
}
  • The 'Mutation' name here we used should be matched with the root mutation name that we are going to register in the Startup.cs.
Now register the name for our mutation and also register our mutation resolver type in the 'Startup.cs'.
Startup.cs:
services.AddGraphQLServer()
.AddQueryType(q => q.Name("Query"))
	.AddType<PersonQueryResolver>()
.AddMutationType(m => m.Name("Mutation"))
	.AddType<PersonMutationResolver>();
  • (Line: 4) Registered root name like 'Mutation' for our GraphQL Mutation type, this name needs to be decorated by every mutation resolver method in our application.

Mutation To Save A Record:

GraphQL Mutation operations are to save the data to the database. Let's implement our save logic using the dapper.
Services/IPersonService.cs:
int SavePerson(PersonDto person)
Services/PersonService.cs:
public int SavePerson(PersonDto person)
{
	using(var conn = Connection)
	{
		var command = @"INSERT INTO Persons(LastName, FirstName, Age)
						VALUES (@LastName, @FirstName, @Age)";

		var saved = conn.Execute(command, param: person);
		return saved;
	}
}
Let's add our mutation resolver method as below:
MutationResolver/PersonMutationResolver.cs:
public int SavePerson(PersonDto person,[Service] IPersonService personService)
{
	return personService.SavePerson(person);
}
The mutation sample looks as below:
mutation($personData:PersonDtoInput){
  savePerson(person:$personData)
}
  • The '$personData' is a GraphQL variable name. The 'PersonDtoInput' is a GraphQL generated input type based on our resolver method input variable type that is 'PersonDto'.
GraphQL variable looks as below:
{
   "personData": {
       "age": "29",
       "firstName": "Gopi",
       "lastName": "P",
       "iD": 0
    }
 }

Support Me!
Buy Me A Coffee PayPal Me

Video Session:

Wrapping Up:

Hopefully, I think this article delivered some useful information integrating HotChocolate GraphQL endpoint into the Asp.Net application using Dapper Micro ORM. I love to have your feedback, suggestions, and better techniques in the comment section below.

Refer:

Follow Me:

Comments

Post a Comment

Popular posts from this blog

Blazor WebAssembly Custom Authentication From Scratch

In this article, we are going to explore and implement custom authentication from the scratch. In this sample, we will use JWT authentication for user authentication. Main Building Blocks Of Blazor WebAssembly Authentication: The core concepts of blazor webassembly authentication are: AuthenticationStateProvider Service AuthorizeView Component Task<AuthenticationState> Cascading Property CascadingAuthenticationState Component AuthorizeRouteView Component AuthenticationStateProvider Service - this provider holds the authentication information about the login user. The 'GetAuthenticationStateAsync()' method in the Authentication state provider returns user AuthenticationState. The 'NotifyAuthenticationStateChaged()' to notify the latest user information within the components which using this AuthenticationStateProvider. AuthorizeView Component - displays different content depending on the user authorization state. This component uses the AuthenticationStateProvider

How Response Caching Works In Asp.Net Core

What Is Response Caching?: Response Caching means storing of response output and using stored response until it's under it's the expiration time. Response Caching approach cuts down some requests to the server and also reduces some workload on the server. Response Caching Headers: Response Caching carried out by the few Http based headers information between client and server. Main Response Caching Headers are like below Cache-Control Pragma Vary Cache-Control Header: Cache-Control header is the main header type for the response caching. Cache-Control will be decorated with the following directives. public - this directive indicates any cache may store the response. private - this directive allows to store response with respect to a single user and can't be stored with shared cache stores. max-age - this directive represents a time to hold a response in the cache. no-cache - this directive represents no storing of response and always fetch the fr

Endpoint Routing In Asp.Net Core

How Routing Works In  Core 2.1 And Below Versions?: In Asp.Net Core routing is configured using app.UseRouter() or app.UseMvc() middleware. app.UseMvc(routes => { routes.MapRoute( name: "default", template: "{controller=Home}/{action=Index}/{id?}"); }); Here in Dotnet Core version 2.1 or below versions on the execution of route middleware request will be navigated appropriate controller matched to the route. An operation or functionality which is dependent on route URL or route values and that need to be implemented before the execution of route middleware can be done by accessing the route path from the current request context as below app.Use(async (context, next) => { if(context.Request.Path.Value.IndexOf("oldvehicle") != -1) { context.Response.Redirect("vehicle"); } else { await next(); } }); app.UseMvc(routes => { routes.MapRoute( name: "vehicleRoute", template: "vehicle", defaul

Asp.Net Core MVC Form Validation Techniques

Introduction: Form validations in any applications are like assures that a valid data is storing on servers. All programing frameworks have their own individual implementations for form validations. In Dotnet Core MVC application server-side validations carried on by the models with the help of Data Annotations and the client-side validations carried by the plugin jQuery Unobtrusive Validation. jQuery Unobtrusive Validation is a custom library developed by Microsoft based on the popular library  jQuery Validate . In this article, we are going to learn how the model validation and client-side validation works in Asp.Net Core MVC Application with sample examples. Getting Started: Let's create an Asp.Net Core MVC application project using preferred editors like Microsoft Visual Studio or Microsoft Visual Studio Code. Here I'm using Visual Studio. Let's create an MVC controller and name it as 'PersonController.cs' and add an action method as bel

.Net5 Web API Managing Files Using Azure Blob Storage

In this article, we are going to understand the different file operations like uploading, reading, downloading, and deleting in .Net5 Web API application using Azure Blob Storage. Azure Blob Storage: Azure blob storage is Microsoft cloud storage. Blob storage can store a massive amount of file data as unstructured data. The unstructured data means not belong to any specific type, which means text or binary data. So something like images or pdf or videos to store in the cloud, then the most recommended is to use the blob store. The key component to creating azure blob storage resource: Storage Account:- A Storage account gives a unique namespace in Azure for all the data we will save. Every object that we store in Azure Storage has an address. The address is nothing but the unique name of our Storage Account name. The combination of the account name and the Azure Storage blob endpoint forms the base address for each object in our Storage account. For example, if our Storage Account is n

.Net5 Web API Redis Cache Using StackExchange.Redis.Extensions.AspNetCore Library

In this article, we are going to explore the integration of Redis cache in .Net5 Web API application using the 'StackExchange.Redis.Exntensions' library. Note:- Microsoft has introduced an 'IDistributedCache' interface in dotnet core which supports different cache stores like In-Memory, Redis, NCache, etc. It is simple and easy to work with  'IDistributedCache', for the Redis store with limited features but if we want more features of the Redis store we can choose to use 'StackExchange.Redis.Extensions'.  Click here for Redis Cache Integration Using IDistributedCache Interface . Overview On StackExchange.Redis.Extnesions Library: The 'StackExchange.Redis.Extension' library extended from the main library 'StackExchange.Redis'. Some of the key features of this library like: Default serialization and deserialization. Easy to save and fetch complex objects. Search key. Multiple Database Access Setup Redis Docker Instance: For this sampl

.NET Core MVC Application File Upload To Physical Location With Buffered Technique

Buffering Technique In File Upload: The server will use its Memory(RAM) or Disk Storage to save the files on receiving a file upload request from the client.  Usage of Memory(RAM) or Disk depends on the number of file requests and the size of the file.  Any single buffered file exceeding 64KB is moved from Memory to a temp file on disk.  If an application receives heavy traffic of uploading files there might be a chance of out of Disk or RAM memory which leads to crash application. So this Buffer technique used for small files uploading. In the following article, we create a sample for the file uploading using .NET Core MVC application. Create The .NET Core MVC Project: Let's create a .NET Core MVC project, here for this sample I'm using Visual Studio Code as below.   Check the link to use the Visual Studio Code for .NET Core Application . IFormFile: Microsoft.AspNetCore.Http.IFormFile used for file upload with buffered technique. On uploading files f

Ionic Picker Sample Code In Angular

Introduction: Ionic Picker(ion-picker) is a popup slides up from the bottom of the device screen, which contains rows with selectable column separated items. The main building block of ion-picker as follows: PickerController PickerOptions PickerController: PickerController object helps in creating an ion-picker overlay. create(opts?: Opts): Promise<Overlay> PickerController create method helps in create the picker overlay with the picker options PickerOptions: PickerOptions is a configuration object used by PickerController to display ion-picker. Single Column Ionic Picker: single.item.picker.ts: import { Component } from "@angular/core"; import { PickerController } from "@ionic/angular"; import { PickerOptions } from "@ionic/core"; @Component({ selector: "single-column-picker", templateUrl:"single.item.picker.html" }) export class SingleItemPicker { animals: string[] = ["Tiger&quo

NestJS File Upload

In this article, we are going to understand the steps to create a file uploading endpoint in the NestJS application. Key Features In NestJS File Upload: Let us know some key features of NestJS file upload before implementing a sample application. FileInterceptor: The 'FileInterceptor' will be decorated on top of the file upload endpoint. This interceptor will read single file data from the form posted to the endpoint. export declare function FilesInterceptor(fieldName: string, localOptions?: MulterOptions): Type<NestInterceptor>; Here we can observe the 'fieldName' first input parameter this value should be a match with our 'name' attribute value on the form file input field. So our interceptor read our files that are attached to the file input field. Another input parameter of 'MulterOptions' that provides configuration like file destination path, customizing file name, etc. FilesInterceptor: The 'FilesInterceptor' will be decorated on t

.Net Core HttpClient JSON Extension Methods Using System.Net.Http.Json Package

.Net Core 3.0 onwards Microsoft brought up a new package called System.Net.Http.Json. This new package provides JSON extension methods for HttpClient. These JSON extension methods will have a prebuild mechanism for serializing or deserializing response data or payload of HttpClient call. System.Net.Http.Json extension methods that are provided to HttpClient, few of them are mentioned below. GetFromJsonAsync PostAsJsonAsync PutAsJsonAsync ReadFromJsonAsync In this article, we understand System.Net.Http.Json package by implementing the HttpClient samples by with and without JSON extension methods and compare them. Create A .Net Core Web API Sample Application: Let's create a .Net Core sample Web API application, from this application we will consume another Web API by implementing HttpClient calls. We can create a Web API sample application using IDE like Visual Studio 2019(Supports .Net Core 3.0 plus) or  Visual Studio Code . Create A Typed Client: In .Net Core using the Http