Windows Phone更改数据库架构

using (ToDoDataContext db = new ToDoDataContext(("isostore:/ToDo.sdf")))
{
        //Create the database schema updater
        DatabaseSchemaUpdater dbUpdate = db.CreateDatabaseSchemaUpdater();

        //Get database version
        int dbVersion = dbUpdate.DatabaseSchemaVersion;

        //Update database as applicable
        if (dbVersion < 5)
        {   //Copy data from existing database to new database 
            MigrateDatabaseToLatestVersion();
        }
        else if (dbVersion == 5)
        {   //Add column to existing database to match the data context
            dbUpdate.AddColumn<ToDoItem>("TaskURL");
            dbUpdate.DatabaseSchemaVersion = 6;
            dbUpdate.Execute();
        }
}