A good way to do such a thing is by going for the Code-first approach in ADO.NET entity framework. After you have created the entities on the server and built a DataContext implementation for them, follow these steps to add entities to your Mono for Android project (If you're using Visual Studio that is).
- Right click the Mono for android project and select Add Existing item
- Select the files you want to add
- Click the small Arrow next to the Open button and choose Link.
Now when you edit the files in the server project or the client, they will stay in sync.
Keep in mind that the set of attributes and API's you can use from the entities is limited. It may take a bit of fiddeling to get things right.
Tip: Use partial classes for adding environment specific behavior and data. Add a second .cs file for each entity class and add any members that you don't want on the client to that file. The same works for client features you only want in your app, but not on the server.
All of the above also works when you work on a mac with MonoDevelop. That application also supports linking items that are on a different location from the .csproj file location.