Network Connection

Hi Xamarin Forum

may I ask how to check network connection every 5 seconds?
I tried the guide written in Stack Overflow https://stackoverflow.com/questions/46852164/always-check-if-there-is-internet-connection-xamarin-forms

I tried to retype the Xamarin.Forms.Device.StartTimer to Device.StartTimer but still

I got the error Not all code paths return a value in lambda expression of Type 'Func' and the error is on =>

what am I missing?