With "Mini C# Pro" you can write and compile C# code on your Android device.
It has the following features
- works off-line
- automatic code indentation
- syntax highlighting
- in case of an error it gives most of the the time clear debug-information
- various code examples
As all paid apps in the Play Store there is a 15 minute window to try out the app for free. In these 15 minutes you can cancel your purchase and reclaim your money.