Check out example codes for "c# httpclient azure function authorization". It will help you in understanding the concepts better.

Code Example 1

//Append URL with code and key or add x-functions-key header.
"https://myazurecloudfunctions.azurewebsites.net/api/SayHi?code=udXhf3pviSICFMtViW/pqmV/1Q5vLH5aMcRWXfD/q6NXk2VVxRlfYw=="

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