How to read AppSettings values from a .json file in ASP.NET Core?

Question

Aryan Kumar · Answer

Sure. Here is how to read appsettings values from a .json file in ASP.NET Core:

Create a .json file and add the appsettings values that you want to read. For example, the following .json file defines an appsetting named "MySetting":

JSON

{
  "MySetting": "My Value"
}

In your ASP.NET Core application, add the following code to your Startup.cs file:

C#

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
  // ...

  // Add the appsettings file to the configuration.
  app.UseAppSettingsFile("appsettings.json");

  // Read the appsetting value.
  var mySetting = app.Configuration["MySetting"];

  // Do something with the appsetting value.
  Console.WriteLine(mySetting);
}

Run your ASP.NET Core application and the appsetting value will be printed to the console.

Here is a breakdown of the code:

The UseAppSettingsFile() method adds the appsettings file to the configuration.
The app.Configuration["MySetting"] property gets the value of the appsetting named "MySetting".
The Console.WriteLine() method prints the appsetting value to the console.

You can also use the ConfigurationManager class to read appsettings values from a .json file. The following code is equivalent to the code above:

C#

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
  // ...

  // Read the appsetting value using the ConfigurationManager class.
  var mySetting = ConfigurationManager.AppSettings["MySetting"];

  // Do something with the appsetting value.
  Console.WriteLine(mySetting);
}

However, the ConfigurationManager class is deprecated in ASP.NET Core 3.0 and later. You should use the app.Configuration property instead.

If you are using a .NET Core 2.1 or earlier version, you can use the ConfigurationManager class to read appsettings values from a .json file. However, it is recommended to upgrade to a newer version of .NET Core and use the app.Configuration property instead.

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How to read AppSettings values from a .json file in ASP.NET Core?

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