AddTable

Using the AddTable method allows you to create a new table for an entity class. On adding a new table, the DatabaseSchemaUpdater also applies the metadata associated with the entity class and creates any related indexes or foreign key constraints.

To add a new entity to the Twitter data model, we first create that entity and decorate it with Table and Column attributes. In the following example, the TwitterFriend class represents a Twitter user, who happens to be a contact of another Twitter user (see Listing 29.10). TwitterFriend contains an Id and a ScreenName property. In addition, an index is declared for the ScreenName property.

LISTING 29.10. TwitterFriend Class

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[Table]
[Index(Columns = "ScreenName")]
public class TwitterFriend : NotifyPropertyChangeBase
{
    string id;

    [Column(IsPrimaryKey = true)]
    public string Id
    {
        get
        {
            return id;
        }
        set
        {
            Assign(ref id, value);
        }
    }

    string screenName;

    [Column]
    public string ScreenName
    {
        get
        {
            return screenName;
        }
        set
        {
            Assign(ref screenName, value);
        }
    }
}

The following code is used to upgrade the schema to include a new table for storing TwitterFriend data:

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using (DataContext dataContext
            = new TwitterDataContext("isostore:Twitter.sdf"))
{
    DatabaseSchemaUpdater updater
                = dataContext.CreateDatabaseSchemaUpdater();
    updater.AddTable<TwitterFriend>();
    updater.Execute();
}

It can be seen from Figure 29.10 that after execution, the Twitter database contains the new table, with a secondary index on the ScreenName column, as desired.

FIGURE 29.10 The TwitterFriend table has been added to the schema.