This article will cover the ways to configure hosting environment in ASP.NET Core application based on the environment on which it is deployed as application behavior can be controlled based on the environment.
The hosting environment in ASP.NET Core is used to indicate at runtime on which environment (Development, Staging, or Production) an ASP.NET Core application is running. There can be different values for Hosting Environment in ASP.NET Core for the same application on different machines/servers and it can be set any single value. Framework provided environments are Development, Staging & Production but you can specify your own values as well i.e. Testing, QA, PrePROD, etc.
Environment variables allow the application to be configured as per the environment on which the application is running.
Why hosting environments?
As part of the software development life cycle, an application has to go through various phases like Development, Testing & Production. We as application developers need to configure different parameters for different environments. i.e. each environment will have its own database (connection string, user id/password, etc), different versions (URL) of third party services, different settings for application features like logging, bundling, minification, exception handling, etc based on the environment (Development, UAT or Production) in which application is running.
Multiple environments let us control these parameters at runtime i.e database connections, third-party service URLs, application behaviour like logging, exception, bundling, etc can be configured environment-wise.
How to configure hosting environment in ASP.NET Core
There are a number of ways to configure the hosting environment ASP.NET Core. This environment variable needs to be set on each machine on which the application is required to run.
using windows command line
To set the environment variable from the command prompt following command can be used. This is applicable for the current session and the app should be started using the dotnet run command.
set ASPNETCORE_ENVIRONMENT=Staging dotnet run --no-launch-profile
using PowerShell
$Env:ASPNETCORE_ENVIRONMENT = "Staging" dotnet run --no-launch-profile
Both command line & PowerShell sets environment variables only for the processes launched from that command window.
using windows environment variables
To configure hosting environment in ASP.NET Core variable globally in windows so that each you don’t need to set it before running the application use windows environment variables
To set environment variable globally open Control Panel ==> System ==> Advanced System Settings ==> Environment Variables ==> System Variable New/Edit & set values in ‘name’ and ‘value’ and click ok
using web.config
Environment variable can be set in web.config as well. Environment variable can be specified for the process in the processPath attribute in web.config. Environment variables set in this section takes precedence over system environment variables.
<aspNetCore processPath="dotnet"
arguments=".\MyApp.dll"
stdoutLogEnabled="false"
stdoutLogFile=".\logs\stdout"
hostingModel="inprocess">
<environmentVariables>
<environmentVariable name="ASPNETCORE_ENVIRONMENT" value="Development" />
</environmentVariables>
</aspNetCore>
Developers can use this to temporarily set the environment to development for debugging purpose.
using Per IIS Application Pool
Environment variable can also be set at IIS pool level for an application running in an isolated application pool. When ASPNETCORE_ENVIRONMENT is set for an app pool, its value overrides a setting at the system level.
<applicationPools>
<add name="CorePool" managedRuntimeVersion="v4.0" managedPipelineMode="Classic">
<environmentVariables>
<add name="ASPNETCORE_ENVIRONMENT" value="Staging" />
</environmentVariables>
</add>
</applicationPools>
AppCmd.exe can be used to add environment variables to the IIS pool level.
appcmd.exe set config -section:system.applicationHost/applicationPools /+"[name='CorePool'].environmentVariables.[name='ASPNETCORE_ENVIRONMENT',value='Staging']" /commit:apphost
Restart IIS or Server after setting the environment variable in IIS for application to have new values available after changes.
How to use hosting environment in ASP.NET Core in your application
Environment based startup class
Below is the example of environment based startup class in which IWebHostingEnvironment has been injected to identify the environment and add code behavior accordingly.
public class Startup
{
public Startup(IConfiguration configuration, IWebHostEnvironment env)
{
Configuration = configuration;
var builder = new ConfigurationBuilder()
.AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true);
}
//Remaining code was removed
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
else
{
app.UseExceptionHandler("/Home/Error");
}
app.UseStaticFiles();
app.UseRouting();
//Remaining code was removed
}
}
In the above code in startup constructor environment variable name has been used to load appsettings.json file based on the environment configured for application i.e. appsettings.development.json or appsettings.production.json file will be used based on the environment set at runtime.
Also in the configure method different application behavior has been set for exception handling based on the environment set at runtime.
How to add custom hosting environment in ASP.NET Core
Development, Staging & Production environments are provided by default by the framework. But ASPNETCORE_ENVIRONMENT can be set to any string value. To configure your own environments following extension class can be added.
public static class HostingEnvironmentExtensions
{
public const string QAEnvironment = "QA";
public const string UATEnvironment = "UAT";
public const string TestEnvironment = "Test";
public static bool IsQA(this IWebHostEnvironment hostingEnvironment)
{
return hostingEnvironment.IsEnvironment(QAEnvironment);
}
public static bool IsUAT(this IWebHostEnvironment hostingEnvironment)
{
return hostingEnvironment.IsEnvironment(UATEnvironment);
}
public static bool IsTest(this IWebHostEnvironment hostingEnvironment)
{
return hostingEnvironment.IsEnvironment(TestEnvironment);
}
}
Once configured it will be available under environment variable as shown below
Summary
Hosting environment in ASP.NET Core allows developers to control how their application will behave in different environments. There are multiple ways available to set an environment variable for the application.
ASP.NET Core has provided 3 environments i.e. development, staging & production by default but custom environments can be added and practically any string can be used for environment name.
References: https://docs.microsoft.com/en-us/aspnet/core/fundamentals/environments?view=aspnetcore-3.1
You can also check my other Article on ASP.NET Core bundling & minification: https://procodeguide.com/programming/asp-net-core-bundling-minification/
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