Adding custom code (.NET) | Fern Documentation

This page covers how to add custom logic and methods to your .NET SDK.

Adding custom logic

To get started adding custom code:

These steps cover adding a new custom file to the SDK. To preserve line-level edits to a generated file, use Replay instead.

Create a new file and add your custom logic

src/YourNamespace/Helper.cs

1 namespace YourNamespace;
2 
3 public static class Helper
4 {
5     public static void MyHelper()
6     {
7         Console.WriteLine("Hello World!");
8     }
9 }

Add your file to `.fernignore`

.fernignore

1 # Specify files that shouldn't be modified by Fern
2 
3 src/YourNamespace/Helper.cs

Consume the helper

Now your users can consume the helper function by importing it from the SDK.

1 using YourNamespace;
2 
3 Helper.MyHelper();

Adding custom SDK methods

Fern also allows you to add custom methods to the SDK itself (e.g. client.my_method() ) by inheriting the Fern generated client and then extending it.

Update `generators.yml` configuration

Name your Fern-generated client something like BaseClient to reflect that this client will be extended.

generators.yml

1 - name: fern-csharp-sdk
2   version: 2.69.1
3   config:
4     client-class-name: BaseClient

Import and extend the generated client

First, import the Fern generated base client and extend it. Then, add whatever methods you want.

src/YourNamespace/MyClient.cs

1 namespace YourNamespace;
2 
3 public class MyClient : BaseClient
4 {
5     public MyClient(ClientOptions? clientOptions = null) : base(clientOptions)
6     {
7     }
8 
9     public void MyHelper()
10     {
11         Console.WriteLine("Hello World!");
12     }
13 }

Update `.fernignore`

Add the MyClient.cs to .fernignore.