Reading Configuration Information in Asp.net Core

Configuration in asp.net core

Asp.net Core supports lots of config providers for different sources such as:

• Command-line Configuration Provider
• Environment Variables Configuration Provider
• File Configuration Provider
• XML Configuration Provider

Two important types of configurations ASP.NET Core supports are:

• app configuration defined in appsettings.json
• host configuration provided through Environment variables prefixed with ASPNETCORE_

Reading configuration from appsettings in asp.net core

Configuration data is available in asp.net core application as key value pairs.Important file for storing configuration data is appsettings.json.Following is how values are stored in appsettings.json

{
"section0": {
"key0": "value",
"key1": "value"
}

We can read it as section name followed by key name:

section0:key0

Read in code

We can read the configuration information from appsettings.json using the configuration API as:

Import Configuration API

using Microsoft.Extensions.Configuration;

Declare class variable

private readonly IConfiguration _config;

Inject in the constructor

public Startup(IConfiguration config)
{
_config = config;
}

or

public HomeController(IConfiguration configuration)
{
_configuration = configuration;
}

Access the configuration information using the configuration API as:

Following will return the value.assuming key is at the root level

Configuration["key"]

if key is in a subsection

"sec2": {
"key1": "val1"
}

Accessing as a strongly typed object

You can use the Configuration.GetValue<T>(key) method for fetching the value from appsettings.json as a strongly typed object:-

var val1 = Configuration.GetValue<int>("key2");
int tot = val1 + 2;

Getting data related to a section

GetSection extracts a configuration subsection with the specified subsection key to access value in a subsection

configuration.GetSection("section2:subsection0");

in a section

configuration.GetSection("section2:subsection0");

Accessing within a subsection

var val1 = Configuration.GetSection("sec2:key1");

if you try to access key as below then you will not get any value.

var val1 = Configuration.GetSection("key1");

To retrieve the configuration value as a specified type

config.GetValue<T>("Key", Default Value);

 

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