Great question! What you are talking about is Xamarin, which is a framework for writing cross-platform apps. If you are already familiar with Microsoft tools, it may help early on, as you will be familiar with the IDE. On a longer interval I advice against using this platform because there will be several drawbacks:
Android and iOS operating systems update frequently. In order to fully utilize these advancements, native implementation is always a better bet.
Any bugs with their wrapper will be bugged until Microsoft decides to fix it
New features on iOS and Android are not always available in Xamarin until later while they catch up their wrappers
If you wanted to build native Android apps, which is our recommendation, use Android Studio and Kotlin language as those are the current recommended standards for Android platform. For iOS the recommendation is to use Swift 5 and target at least iOS 11 and newer and Xcode IDE.
Cross-platform frameworks may sound cool and useful initially, but are not necessarily production ready and often cause more problems than benefit.