Added `Encrypting Setting Values in the Application Configuration`section.

Resolve #21900

docs/en/framework/infrastructure/settings.md

@@ -160,6 +160,39 @@ Setting values should be configured under the `Settings` section as like in this
 
 > `IConfiguration`  is an .NET Core service and it can read values not only from the `appsettings.json`, but also from the environment, user secrets... etc. See [Microsoft's documentation](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration/) for more.
 
+#### Encrypting Setting Values in the Application Configuration
+
+You have to use the `ISettingEncryptionService` to encrypt the setting values when the `IsEncrypted` property of a setting definition is set to `true`, which means that the setting value should be encrypted in the `appsettings.json`.
+
+Example of injecting the `ISettingEncryptionService` into a class and encrypting the plain text:
+
+````csharp
+public class MyService
+{
+    private readonly ISettingEncryptionService _encryptionService;
+
+    public MyService(ISettingEncryptionService encryptionService)
+    {
+        _encryptionService = encryptionService;
+    }
+
+    public void EncryptValue(string plainText)
+    {
+        var ciphertext = _encryptionService.Encrypt(plainText);
+    }
+}
+````
+
+Then, Replace `ENCRYPTED_VALUE_HERE` with the ciphertext generated by `ISettingEncryptionService.Encrypt` method.
+
+````json
+{
+  "Settings": {
+    "MySetting": "ENCRYPTED_VALUE_HERE"
+  }
+}
+````
+
 ### Custom Setting Value Providers
 
 If you need to extend the setting system, you can define a class derived from the `SettingValueProvider` class. Example: