TipCalc is based on an existing iOS and Android sample but has been completely rewritten for Xamarin.Forms using XAML and data-binding. This new version now builds for iOS, Android, and Windows Phone.
If you open the solution in Xamarin Studio, it will not be able to load the Windows Phone project; and if you open the solution in Xamarin Studio under Windows, it will not be able to load the iOS project either.
TipCalc lets you type in a food-and-drink subtotal and a post-tax total from your restaurant bill and then select a tip percentage. It applies the percentage to the food-and-drink subtotal and adds the result to the post-tax total, rounded to the nearest quarter.
The solution contains four projects: the iOS, Android, and Windows Phone projects are small and standard Xamarin.Forms stub applications. All the common application code is in the TipCalc portable class library. The calculations are handled in aTipCalcModel class, and the entire user interface is realized in XAML in the TipCalcPage.xaml file. Two data-binding value converters help massage the data between the data model and the XAML file.
Author : https://github.com/rzaitov.
If you like this tutorial then you can download full copy of the code from github.