Skip to main content

Part-1 An Overview On GraphQL Implementation In .Net Application Using Hot Chocolate Library

In this article, we are going to understand the implementation steps of GraphQL in .Net5 application using Hot Chocolate Library.


GraphQL is an open-source data query and manipulation 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, NetsJS, etc and it isn't tied to any specific database or storage engine and instead backed by your existing code and data.

GraphQL caries two important operations:

  • Query - fetching data
  • Mutation - save or update.

Hot Chocolate GraphQL:

Hot Chocolate is an open-source GraphQL server that is compliant with the newest GraphQL latest specs. It is the wrapper library of the original .Net GraphQL library. Hot Chocolate takes the complexity away from building a fully-fledged GraphQL server.

An Overview On GrphQL SDL(Schema Definition Language):

A syntax to data query and manipulation in GraphQL called SDL(schema definition language). GraphQL SDL syntax looks similar to the javascript object. Hot Chocolate GraphQL library providers flexibility to develop GraphQL endpoint either using Schema First approach(purely uses GraphQL SDL syntax) or using Code First approach(in this approach framework will take responsibility of generating GraphQL SDL implicitly for dotnet developers this will be ideal approach). So this section is to get familiar with GraphQL SDL syntax for better understanding.

GraphQL SDL syntax to define 'type'(in c# class is equivalent to the GraphQL SDL 'type') object(in c# it is like our database table representing class). 

type Book {
  Id: Int
  Name: String
  • Here we defined the 'Book' GraphQL SDL type object. Its properties are 'Id', 'Name'. Its properties types are like 'Int', 'String' are GraphQL scalar types.
GraphQL SDL syntax to define the Query type.
type Query {
  book: Book
  • This 'Query type' is an entry point to fetch data. It contains all resolvers(means logic to fetch data).
  • Here we define 'book: Book' means on requesting 'book' query we get a response of single object of type 'Book', similarly we need to define all fetch logic inside of the 'Query'.
GraphQL SDL syntax to define the Mutation type.
type Mutation{
  • The 'Mutation type' contains all the logic for saving or updating the data.
  • Here 'create(book: BookInput)' is the resolver method to save data.
GraphQL SDL syntax to define the Schema type.
type Schema{
  • Schema is the root type in GraphQL where 'Query' and 'Mutations' registered.
Note: No need to remember all the syntax above mentioned here I'm going to explain integration using a code-first approach where we don't need to write SDL syntax.

Create A .Net5 Web API Application:

Let's create a .Net5 Web API application in which we are going to integrate GraphQL. For development, any IDE can be used but most preferred are Visual Studio 2019(Version 16.8.* that supports .Net5) or Visual Studio Code.

Hot Chocolate Library:

Package Manager Command:
Install-Package HotChocolate.AspNetCore -Version 11.0.2
.Net CLI Command:
dotnet add package HotChocolate.AspNetCore -Version 11.0.2

Register GraphQL Service And Endpoint:

First we need to register our GraphQL service that is 'AddGraphQLServer()'. This 'AddGraphQLServer()' extension method enables schema and executor.
Startup.cs:(ConfigureServices Method)
Now configure GraphQL endpoint.
Startup.cs:(Configure Method)
app.UseEndpoints(endpoints =>

POCO Class And GraphQL ObjectType:

A plain class is a general used to represent a table for fetching the data in .Net application. So lets create a POCO(Plain Old CLR Object) class that will type for our data return form the server.
namespace HC.GraphQL.Sample.Data.Entities
  public class Gadgets
   public int Id { get; set; }
   public string ProductName { get; set; }
   public string Brand { get; set; }
   public decimal Cost { get; set; }
   public string Type { get; set; }
Now GraphQL doesn't understand our 'Gadget.cs' .net class because GraphQL can only understand SDL syntax. So to make our POCO class understand by GraphQL we need to map it with 'HotChocolate.Types.ObjectType'. In this 'ObjectType' we need to register all our POCO class properties so that on runtime 'ObjecType' generates GraphQL SDL type which is understandable by the GraphQL execution schema.
So let's create a 'HotChocolate.Types.ObjectType' for our 'Gadget' class.
using HC.GraphQL.Sample.Data.Entities;
using HotChocolate.Types;

namespace HC.GraphQL.Sample.ObjectTypes
  public class GadgetsObjectType : ObjectType<Gadgets>
   protected override void Configure(IObjectTypeDescriptor<Gadgets> descriptor)
	descriptor.Field(g => g.Id).Type<IntType>().Name("Id");
	descriptor.Field(g => g.ProductName).Type<StringType>().Name("ProductName");
	descriptor.Field(g => g.Brand).Type<StringType>().Name("Brand");
	descriptor.Field(g => g.Cost).Type<DecimalType>().Name("Cost");
	descriptor.Field(g => g.Type).Type<StringType>().Name("Type");
  • Here we create 'GadgetsObjectType' that inherits 'HotChocolate.Types.ObjectType<Gadgets>'.
  • Inside the 'Configure' method we are registering the properties of 'Gadget' classes as the 'Field' to the ObjectType.
  • Here 'IntType','StringType','DecimalType' are scalar types provided by the HotChocolate GraphQL library.
  • The 'Name()' extension method to define the name of each 'Field' registered.
Now on runtime, the 'GadgetsObjectType' generates the GraphQL type as below
type Gadgets{
    Id: Int,
    ProductName: String,

Create Query And Its ObjectType:

In GraphQL 'Query' type is the entry point for fetching the data. So let's create our query class.
using HC.GraphQL.Sample.Data.Entities;

namespace HC.GraphQL.Sample.SchemaCore
  public class Query
   public Gadgets FirstGadget()
	return new Gadgets{
	 Id = 1,
	 ProductName = "Samsung M30s",
	 Brand = "Samsung",
	 Cost = 15000,
	 Type = "Mobile"
  • Here 'FirstGadget()' method is our resolver method where we fetching a single record.
Since 'Query' is a normal c# class we need to create an ObjectType for it.
using HC.GraphQL.Sample.SchemaCore;
using HotChocolate.Types;

namespace HC.GraphQL.Sample.ObjectTypes
  public class QueryObjectType:ObjectType<Query>
   protected override void Configure(IObjectTypeDescriptor<Query> descriptor)
	descriptor.Field(g => g.FirstGadget())
  • Here we registered our resolver method 'FirsGadget()' as a field for QueryObjectType. 
  • Defined its 'Type' as 'GadgetsObjectType'(This GadgetObjectType represents our c# gadget class for GraphQL).
  • The 'Name' extension method defines the name for the field.
On runtime, this QueryObjectType represents the schema like as below.
type Query{
  FirstGadget: Gadgets

Register Query:

Now we need to register our 'QueryObjectType' in the Startup file
Startup.cs:(ConfigureServices Method)


GraphQL is about asking for specific fields on objects on the server. Let's test API by requesting Fields.
Request Query:
  • Here 'query' to invoke the 'QueryObjectType'. The name 'FirstGadget' should match with the registered name in 'QueryObjectType' so this will invoke the specific resolver method on our server-side. In the above request, we are asking the server only to send 2 properties.
Now run the application and navigate to route '/graphql' which opens the GraphQL tool called 'Bana Cake Pop' provided by HotChocolate for easy querying.

Create A Resolver Method To Fetch Multiple Records:

Now let's add a new resolver method in the 'Query' class that returns multiple records.
public List<Gadgets> AllGadgets()
  return new List<Gadgets>
	new Gadgets{
	Id = 1,
	ProductName = "Samsung M30s",
	Brand = "Samsung",
	Cost = 15000,
	Type = "Mobile"
   new Gadgets{
	Id = 2,
	ProductName = "Think Pad",
	Brand = "Lenovo",
	Cost = 75000,
	Type = "Laptop"
Now register this 'AllGadgets' resolver method as a field in the 'QueryObjectType'.
descriptor.Field(g => g.AllGadgets())
  • Here 'ListType' GraphQL type that is equivalent to 'List'
In the next part, we will implement database integration, passing query parameters to filter data and GraphQL mutations.

Support Me!
Buy Me A Coffee PayPal Me

Wrapping Up:

Hopefully, I think this article delivered some useful information on implementing Hot Chocolate GraphQL in .Net5 Application. I love to have your feedback, suggestions, and better techniques in the comment section below.


Follow Me:


  1. Hi Naveen, I've implemented a few graphql servers in dotnet, but I have always had trouble consuming it from a client i.e an app or website and I'd be interested to hear if you'd do a chapter exclusively on actually consuming it, ideally using Blazor
    Many thanks,

    1. Hi Mani

      I made blog using angular

      I tried using blazor library like Strawberry Shake(Hot Chocolate GraphQL library)
      but currently i'm facing some issue with it.


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

.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

.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

GraphQL API Integration In Asp.Net Core Application

Introduction: GraphQL 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 ASP.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. How GraphQL API Different From Rest API: GraphQL exposes a single end-point or route for the entire application, regardless of its responses or actions. HTTP-POST is the only Http verb recommended by the GraphQL. The client applications (consumers of API) can give instructions to GraphQL API about what type of properties to be returned in the response. Building Blocks Of GraphQL API: The main building blocks of GraphQL API is Schemas and Types.  A 'Schema' in GrpahQL API describes the functionality available to the clients connect to API. Schema mostly consists of GraphQL Object Types, Queries, Mutations, etc. T

ASP.NET Core Web API Versioning

Introduction: An iteration and evolutionary changes of an ASP.NET Core Web API is handled by Versioning. Versioning of an API gives confidence to the clients which consumes API for a long time. Any changes or development of an API will be accessible using the new version and it won't cause issues to the clients consuming the old version of API. When To Use Versioning: Any API response changes. Developing an API by implementing testing levels like 'Alpha', 'Beta', and 'RC' versions before releasing Production. Deprecating an API which means API going to be removed or upgraded by a version within a short period. Versioning Types: Query String Versioning Url Path Versioning Media Type Versioning API Version Nuget: To Configure versioning to AspNet Core Web API Microsoft provided a library(Microsoft.AspNetCore.Mvc.Versioning). So to use the versioning library please install NuGet below.              Install-Package Microsoft.A

Blazor Server CRUD Operations

Introduction: Blazor Server is a web framework to develop server-side single-page applications. Blazor is made up of components with the combinations on C#, Html, CSS.  Blazor Server is production-ready from the .Net Core 3.0.  Blazor Server Working Mechanism: Blazor Server is a very light-weight web development framework.  In Blazor Server, not all code gets downloaded to the client browsers. Blazor Server made of components these components can be a block of code or page with respective navigation.  Blazor server application communicates with the server with a SignalR background connection which is inbuilt functionality. Application click,  form submission, change events, application page navigation every operation is carried out by the SignalR connection by communicating with the server.  Blazor updates the Html DOM very gently on every data update without any overhead. Blazor Server application maintains a nice intelligent tree structure to update the required inform