How to create an envelope with a Payment Item field using the C# .NET SDK

Hi Team,

I am implementing the DocuSign Payments feature using the C# .NET SDK and would appreciate some guidance.

My requirement is to:

• Upload a PDF document through my ASP.NET Core Web API.
• Create a new envelope programmatically (without using an existing envelope ID).
• Add a signer.
• Add a Payment Item field to the envelope.
• Configure a payment amount.
• Send the envelope so that the signer is prompted to make the payment during the signing process.

I have reviewed the Payments documentation and several community posts, but I could not find a complete REST API or C# SDK example that demonstrates how to create the Payment Item field programmatically.

Could someone please clarify the following?

1. Which REST API endpoint or .NET SDK classes should be used to add a Payment Item field while creating an envelope?
2. Is the Payment Item field represented as a Formula Tab with a paymentDetails object, or is there another recommended approach?
3. Is there a complete C# (.NET) example that uploads a PDF, creates an envelope, configures the Payment Item field, and sends the envelope?
4. Is there any official documentation that explains how to implement this feature using the eSignature REST API and .NET SDK?

Any guidance, sample code, or documentation links would be greatly appreciated.

Thank you!