Hi A L,
Thank you for reaching out to Microsoft Q & A forum.
I have finished the tutorial exercise on, Creating a Web API Project , and I found the instructions straightforward and easy to follow. Following them, I managed to set up a new API application.
Before going through the .http files you must install REST Client extension
Then after going through explore with .http files.
1.Open the ContosoPizza.http file.
This file has been pre-configured with the @ContosoPizza_HostAddress variables and a GET command calling /weatherforecast/ that accepts application/json.
2.Select the Sent Request command above the GET which will send a request to the running service.
I've attached a screenshot for your reference.
Explore with .http files: If you encounter any future issues, please feel free to contact us, and we will be pleased to assist you further.
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Thank you.