You have two options to expose data as a service using WCF Data Services:
Use a relational database as the data source
Use a data source other than a relational database
If you are using a relational database as the data source, you can use LINQ to SQL or Entity Framework to expose the data. On the other hand, you can use collections of objects as a data source too. In either case, you need to create a WCF Data Service using the designer. In the next section, we will discuss how we can create an ADO.NET Data Service.