Skip to main content

Configuration And Working Mechanism Of JSON Files On .Net Core Application Starts


.Net Core application JSON file configuration technique has come into picture by replacing traditional way like Web.Config file approach. By default application loads "appSettings.json" file on startup. If we have defined environment variable then application also loads environmental specific json files like "appSettings.Development.json"(for environment variable is Development), "appSettings.Stage.json"(for environment variable is Stage), "appSettings.Production.json"(for environment variable is Production) along with the "appSetting.json".

Create A Sample .Net Core Application:

Now for better understanding let's walk through with a sample .Net Core Web API application. The application can be created either by using Visual Studio 2019(VS Editor supports .Net Core Version 3.0plus) or visual Studio Code

App Loads appSettings.json And appSettings.{Environmental_Variable}.json By Default:

On application start, appSettings.json and appSettings.{Environment_Variable}.json file automatically loaded by the application and injected those file values into the Microsoft.Extensions.Configuration.IConfiguration in Startup file. So let's add debugger in Startup.cs file and inspect the JSON files as below.
Here in the picture, we can observe that appSettings.json and appSettings.Development.json are loaded on the app starts.

Let's change the 'Environmental variable' to confirm based on setting the file will get loaded.

In Visual Studio Code editor to set the environment variable for testing open the launch.json file in '.vscode' folder as below

For Visual Studio 2019 or 2017 open launchSettings.json file in 'Properties' folder.

Now let change the environmental variable to 'Stage' and check the Startup.cs file by running application in debug mode as below.

Values Of appSettings.json Override By appSetting.{Environmental_Variable}.json:

Till now we learnt along with appSetting.json file environmental variable json files get loaded on application starts. One more important thing to remember is appsettings.json file values will be overridden by appsettings.{environmental_variable}.json while reading the settings in the application. So properties name should be matched in both files to get the benefit of the override mechanism.

Let's understand this overriding concept by implementing a sample endpoint. Now in "appsetting.json" file add new object property as below
appsettings.json:
{
  "MyUser":{
    "VariableName":"Production"
  }
}
Let's add a model to represent the above JSON object
Model/MyUser.cs:
public class MyUser
{
	public string VariableName{get;set;}
}
Now register 'MyUser' object with the json object in Startup.cs as below
Startup.cs:
public void ConfigureServices(IServiceCollection services)
{
	services.Configure<Models.MyUser>(Configuration.GetSection("MyUser"));
}
Now let's create a testing endpoint as below.
Controllers/TestController.cs:
[Route("test")]
public class TestController : ControllerBase
{
	private readonly MyUser _myUser;
	public TestController(IOptions<MyUser> myUser)
	{
		_myUser = myUser.Value;
	}
	[Route("get")]
	public IActionResult Get()
	{
		return Ok(_myUser);
	}
}
#L5 at this line number 'MyUser' object gets injected into the constructor using 'Microsoft.Extension.Options.IOption<MyUser>

Now run the application and output shows as below.
Now override the appsettings.json values with the appsettings.Development.json file values
appsettings.Development.json:
{
  "MyUser":{
    "VariableName":"Development"
  }
}
Now re-run the application and output shows like appsettings.Development.json values override the appsettings.json values as below.

Load Custom JSON File:

Configuring everything into the appsettings.json file is good, but there are cases where a large number of settings need to be read from a file(which are not suitable to store in Database) in that case adding everything into the appsettings.json makes the file more tedious and confusing. So it is always best to practise to maintain separate JSON files in this kind of scenarios. After separating settings into the custom file we need to configure the custom file to load at the time of application starts just like the appsettings.json.

Let's add a sample JSON file like 'myCustom.json' at the location(the root of the application) where appsettings.json existed.
Now in Program.cs file we need to use an extension method of IHostBuilder like 'ConfigureAppConfiguration' method. This method helps to add n-number of custom JSON files which gets loaded on application starts.
Program.cs:
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureAppConfiguration((hoistingContext, config) => {
	config.AddJsonFile("myCustom.json");
})
.ConfigureWebHostDefaults(webBuilder =>
{
	webBuilder.UseStartup<Startup>();
});
#L4 at this we are adding our custom JSON file inside of the 'ConfigureAppConfiguration' methods. So this file will get loaded automatically along with appsettings.json file.

Now run the application in debug mode and we can see 'myCustom.json' file loaded.

Load Custom JSON File Based On Environmental Variable:

We can load custom files based on environment variable configured for the application.

Let's add files with environment variable inside of their file name as below.
Now update the "ConfigureAppConfiguration" method  in Program.cs file as below.
Program.cs:
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureAppConfiguration((hoistingContext, config) => {
	config.AddJsonFile($"myCustom.{Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT")}.json");
})
.ConfigureWebHostDefaults(webBuilder =>
{
	webBuilder.UseStartup<Startup>();
});
#L4 at this line using 'System.Environment.GetEnvironmentVariable()' method is used to fetch variable value.

Now run the application in debug mode and output as shown below.

Load JSON File From Custom Path:

Previously we have created custom JSON file in the root path, so we simply specified file name in Program.cs. If we have more number of custom JSON file it is good to maintain them inside of the folders.

Let's add our custom JSON file inside of the 'wwwroot' folder as below.
Update the Program.cs file as below.
Program.cs:
public static IHostBuilder CreateHostBuilder(string[] args) =>
	Host.CreateDefaultBuilder(args)
	.ConfigureAppConfiguration((hoistingContext, config) => {
		config.AddJsonFile("wwwroot/Config/myCustom.json");
	})
	.ConfigureWebHostDefaults(webBuilder =>
	{
		webBuilder.UseStartup<Startup>();
	});
#L4 at this line JSON file configured with the full file path.

Now run the application in debug mode and output shown below.

Wrapping Up:

Hopefully, I think this article delivered some useful information about loading of appsetting.json and custom JSON files in .Net Core application. I love to have your feedback, suggestions, and better techniques in the comment section below.

Follow Me:

Comments

Popular posts from this blog

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", defaults:new { …

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.Types likely to be called Grap…

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 VersioningUrl Path VersioningMedia 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.AspNetCore.Mvc.Versioning -version 4.0.0 Register API V…

.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 from the client, then the entire …

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: PickerControllerPickerOptions 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", "Lion", "Elephant"…

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 below.
PersonController.cs: us…

Blazor WebAssembly Dynamic Form Validation

Introduction: In Blazor WebAssembly(client-side framework) form validation can be done with Data Annotations. Using Data Annotations we can validate form either by default validation attributes or by creating custom validation attributes. Using this Data Annotation attribute we can dynamically add or remove validation on a specific field in a form.
Create Blazor WebAssembly Project: To create a Blazor WebAssembly template project need to install the latest version of VisualStudio 2019 for rich intelligence support or we can use VisualStudio code but less intelligence support from the editor. Click here to know about Blazor WebAssembly template creation. Blazor WebAssembly is in preview mode, not yet ready for production.
Create Razor Component: After creating a sample project using the Blazor WebAssembly template, in "Pages" folder add new Razor Component, name it as "UserForm.razor"
Add Route: In Blazor routing can be configured using @page  directive, and URL should b…

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 information or changed …

NestJS API CRUD Operations With MongoDB

Introduction: NestJS is a framework used to develop server-side applications. NestJS built on top of Node.js frameworks like Express. It is a combination of Progressive Javascript, Object-Oriented Programming, Functional Programming, and Functional Reactive Programming.
Nest CLI Installation: Using Nest CLI we are able to generate the NestJS starter project with the default template. To install Nest CLI globally over our system open command prompt and run the command
npm i -g @nestjs/cli Now create a sample project by using Nest CLI command  nest new your_project_name package.json: Now open the package.json file from the sample application created, you can observe few properties like "scripts", "dependencies", and "devDependencies".
"dependencies" contains all plugins to be installed and used them to run the application.
"devDependencies" contain all plugins to be installed and used them at the time of application development.
"scrip…

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-ControlPragmaVary 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 fresh response from serverno-store…