ASP.NET - Configuration Providers

Configuration providers supply key-value settings to an ASP.NET Core application. Each provider loads data from a different source, such as files, memory or environment variables. Multiple providers can be combined so the app reads configuration from all available inputs.

Built-in Providers
ASP.NET Core includes providers for JSON files, environment variables, command-line arguments, INI files, XML files and in-memory collections. These cover most needs without custom code. Apps can mix providers to support flexible deployment patterns.

Load Order and Precedence
Providers load in sequence. Values from later providers overwrite earlier ones. For example, an environment variable can override a value from appsettings.json. This priority order allows sensitive or environment-specific settings to replace defaults safely without editing code.

Adding Providers in Program Setup
The Host builder configures providers automatically, but developers can customize the pipeline. Providers are added in ConfigureAppConfiguration. This lets teams insert new sources or remove defaults depending on deployment requirements.

Custom Providers
If built-in providers are not enough, developers can create a custom provider that reads configuration from new locations such as databases, APIs or encrypted files. Custom providers inherit from ConfigurationProvider and implement loading logic that fills the data dictionary.

Why Providers Matter
Providers keep configuration flexible and independent of code. Applications can move between environments, scale across servers or switch cloud platforms without changing source files. Only provider order and data sources need adjustment.

Example

var builder = WebApplication.CreateBuilder(args);

builder.Configuration
    .AddJsonFile("extra.json", optional: true)
    .AddEnvironmentVariables()
    .AddInMemoryCollection(new Dictionary<string, string>
    {
        ["FeatureX:Enabled"] = "true"
    });

var app = builder.Build();

app.MapGet("/", () => builder.Configuration["FeatureX:Enabled"]);

app.Run();

Behavior

• Base JSON loads first

• Environment variables override when present

• In-memory values override everything before them