RadzenUpload and base64

Good evening, I was wondering if it was possible to get a base64 from a RadzenUpload.

No, but you can use RadzenFileInput:

my problem is that using RadzenFileInput I can only insert small files

Yes, it can be used for small files only. Large file converted to base64 string will be even larger.

using RadzenUpload in which format can I save the data on the db?

The file is received server side in the controller used for upload as IFormFile:

you can inject your database context in this controller, read the file and add/update relevant record. In this demo there is an example how to add additional parameter:

but these are API, I am using a brazor server approach. within these API I will not be able to call the methods present in the components that I need to work my data.

I'm afraid that I cannot add anything else - check again my previous reply

let me explain better, I put your code in a razor component, but I can't make InvokeAsync work, it doesn't call the desired function

You cannot put this code in a razor component. It's a server-side razor controller. Again, read my reply on how to add parameters to upload, to inject the EF context, to find the relevant record, to read the file and update desires record field.