C# in Depth

318 CHAPTER 12 LINQ beyond collectionsListing 12.1Adding a constructor to the User entity classpublic partial class User{public User (string name, UserType userType): this(){Name = name;UserType = userType;}}It’s important to call the parameterless constructor from our new one—the generatedcode initializes some members there. In the same way as we added a constructor, wecan override ToString in all the entities, so that the results will be exactly as they werein chapter 11. The generated code contains many partial method declarations, so youcan easily react to various events occurring on particular instances.At this point, we can simply copy over the SampleData.cs file from chapter 11 andbuild the project. Now for the tricky bit—copying the sample data into the databasefrom the in-memory version.12.1.2 Populating the database with sample dataOK, I lied. Populating the database is ludicrously easy. Listing 12.2 shows just how simpleit is.Listing 12.2Populating the database with our sample datausing (var context = new DefectModelDataContext()){context.Log = Console.Out; C Enables console logging Bcontext.Users.InsertAllOnSubmit(SampleData.AllUsers);context.Projects.InsertAllOnSubmit(SampleData.AllProjects);context.Defects.InsertAllOnSubmit(SampleData.AllDefects);context.NotificationSubscriptions.InsertAllOnSubmit(SampleData.AllSubscriptions);Populatescontext.SubmitChanges();Flushes changes entities}to databaseECreatescontext towork inI’m sure you’ll agree that’s not a lot of code—but all of it is new. Let’s take it one stepat a time. First we create a new data context to work with B. Data contexts are prettymultifunctional, taking responsibility for connection and transaction management,query translation, tracking changes in entities, and dealing with identity. For the purposesof this chapter, we can regard a data context as our point of contact with thedatabase. We won’t be looking at the more advanced features here, but there’s oneuseful capability we’ll take advantage of: at C we tell the data context to write out allthe SQL commands it executes to the console.The four statements at D add the sample entities to the context. The four propertiesof the context (Users, Projects, Defects, and NotificationSubscriptions) areDLicensed to Rhona Hadida