C# demo app

I'm building a demo app in C# but am very rusty and need some help. It is a WASM front-end that hits a .net api. The front-end passes an uploaded file to the api, then the api passes that to a container/service that encrypts the file and passes the result back to the api, then the api passes back to the front-end as a downloaded file. I need help today/asap

It would be a plus if you are savvy with cloud architecture as well, such as deploying it into a cloud environment.