I am pretty new to this topic, I want to understand how key vault secures my environment.
If someones get my Keyvault Url is it possible to easily get my secrets, keys stored using that URL by using some dot net code and default credentials to azure ??
No, by having the public URL alone users will not be able to access the secrets, keys stored. You need to add that user and provide the right policy to access those using the access policy.
However if you are deploying this application to production, its better to have Private endpoint and firewall created for the specific IPs only. You can read the best practices from here.
