How to change environment in ASP.NET Core?

By setting the ASPNETCORE_ENVIRONMENT environment variable.

ASP.NET Core Environments - Development, Staging, Production

💡 Concept Name

ASP.NET Core Hosting Environments

📘 Quick Intro

ASP.NET Core supports multiple hosting environments: Development, Staging, and Production. The application behavior, configuration, and error handling can vary based on the environment, making your app more flexible and secure.

🧠 Analogy / Short Story

Imagine you're rehearsing a play. You rehearse at home (Development), perform a full dress rehearsal on stage (Staging), and finally go live in front of an audience (Production). Each stage has different settings and checks. ASP.NET Core environments work the same way.

🔧 Technical Explanation

The environment is defined using the ASPNETCORE_ENVIRONMENT variable. Common values:

Development: Enables detailed errors, DeveloperExceptionPage, Hot Reload
Staging: Mimics production, used for final testing
Production: Optimized for performance and security

You can load different appsettings.{Environment}.json files and conditionally add middleware or logging based on the current environment.

🎯 Purpose & Use Case

✅ Separate config for dev/staging/prod
✅ Enable debugging tools only in development
✅ Prevent detailed errors in production
✅ Test deployment pipeline in staging

💻 Real Code Example

// Program.cs (ASP.NET Core 6+)
var builder = WebApplication.CreateBuilder(args);

var env = builder.Environment;

builder.Configuration
    .AddJsonFile("appsettings.json")
    .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true);

var app = builder.Build();

if (env.IsDevelopment()) {
    app.UseDeveloperExceptionPage();
} else {
    app.UseExceptionHandler("/Home/Error");
}

❓ Interview Q&A

Q1: What are the default environments in ASP.NET Core?
A: Development, Staging, Production

Q2: How do you set the current environment?
A: Set the ASPNETCORE_ENVIRONMENT variable.

Q3: What happens in Development environment?
A: Developer tools and error pages are enabled.

Q4: Is DeveloperExceptionPage shown in Production?
A: No, it's only enabled in Development.

Q5: How can you check environment in code?
A: Use IHostEnvironment or IWebHostEnvironment.

Q6: Which JSON file is loaded based on environment?
A: appsettings.{Environment}.json

Q7: Why use Staging environment?
A: For testing before production release.

Q8: Can you create custom environments?
A: Yes, any string like "QA" or "Testing" works.

Q9: How to use different middleware based on environment?
A: Use env.IsDevelopment(), etc. in Program.cs

Q10: What's the benefit of environment-specific config?
A: Keeps sensitive or dev-only settings isolated and secure.

📝 MCQs

Q1. What are the three main environments in ASP.NET Core?

Debug, Release, Live
Dev, Preprod, Stable
Development, Staging, Production
Alpha, Beta, Release

Q2. Which environment enables DeveloperExceptionPage?

Production
Staging
Development
QA

Q3. How to set the environment variable?

ENV
DOTNET_ENV
APP_ENV
ASPNETCORE_ENVIRONMENT

Q4. What is used to check current environment in code?

IEnv
IWebLogger
IHostEnvironment
IConfig

Q5. Which file is loaded for Development?

app.Development.config
settings.dev.json
appsettings.dev.json
appsettings.Development.json

Q6. Is it possible to create custom environment like 'QA'?

No
Only in .NET Framework
Yes
Only in Production

Q7. What happens in Production environment?

All logs shown
Hot reload enabled
Error pages hidden, optimized performance
Nothing changes

Q8. What is the environment-aware logging config called?

Custom filter
Error filter
LogMode
Logging section per environment

Q9. What method checks for Staging environment?

env.Stage()
env.CheckStaging()
env.IsStage()
env.IsStaging()

Q10. Why separate environment configs are useful?

To speed up coding
For multiple users
To isolate settings for each stage
To debug only

💡 Bonus Insight

You can set ASPNETCORE_ENVIRONMENT in launchSettings.json during development, in environment variables on a server, or in Azure App Service settings for deployment.

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What are the different environments in ASP.NET Core?