The CRM Web API Preview is nicely documented but I am missing an article explaining how to generate strongly typed objects from the metadata document to use with server side code. The following walkthrough describe just that:
2. Download the MetaData document: Navigate to the Metadata document URL ([organization URI]/api/data/$metadata) with your browser. You should get an XML file describing your Organization Metadata.
To download, save (Ctrl+S in Chrome) the file to any directory you wish.
3. Install OData v4 Client Code Generator VS Extension in Visual Studio and Restart Visual Studio
4. Add OData Client item to your VS project
5. Edit the newly created OData file, insert the Metadata file location (step 2) as the MetadataDocumentUri constant value and save the file.
The OData v4 Client Code Generator should automatically generate a .cs file with strongly typed objects to match the Metadata document.
6. Consume the newly created classes in your code