10.Local Database & LINQ
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LINQ to SQL allows accessing local SQLite databases on Windows Phone. It supports queries, inserts, updates and deletes through a data context. The database schema can be upgraded by adding or removing tables and columns. Performance best practices include keeping change sets small and submitting changes frequently to avoid data loss.
![Database Creation: Example
// Define the tables in the database
[Table]
public class Wine : INotifyPropertyChanged, INotifyPropertyChanging
{
private string wineID;
private string name;
[Column(IsPrimaryKey=true)]
public string WineID
{
get { return wineID; }
set {
InvokePropertyChanging(new PropertyChangingEventArgs("WineID"
));
wineID = value;
InvokePropertyChanged(new PropertyChangedEventArgs("WineID"))
;
}
}
[Column]
public string Name { ... }
...
}
Define Tables](https://image.slidesharecdn.com/10-sessionv2-140816042452-phpapp01/85/10-Local-Database-LINQ-12-320.jpg)
![Example: Parent Object
[Table]
public class Contact : INotifyPropertyChanged, INotifyPropertyChanging
{
// Fields
private EntitySet<Lead> leads = new EntitySet<Lead>();
[Association(Storage = "leads", OtherKey = "ContactID")]
public EntitySet<Lead> Leads
{
get { return this.leads; }
set {
InvokePropertyChanging(
new PropertyChangingEventArgs("Leads"));
this.leads.Assign(value);
InvokePropertyChanged(
new PropertyChangedEventArgs("Leads"));
}
}](https://image.slidesharecdn.com/10-sessionv2-140816042452-phpapp01/85/10-Local-Database-LINQ-21-320.jpg)
![Example: Child Object
[Table]
[Index (Name="ContactID_Idx", Columns="ContactID", IsUnique=false)]
public class Lead : INotifyPropertyChanged, INotifyPropertyChanging
{
private EntityRef<Contact> contact;
[Column]
public long ContactID {get; set; }
[Association(Storage = "contact", ThisKey = "ContactID", IsForeignKey=true)]
public Contact Contact
{
get { return this.contact.Entity; }
set {
InvokePropertyChanging(new PropertyChangingEventArgs("Contact"));
this.contact.Entity = value;
InvokePropertyChanged(new PropertyChangedEventArgs("Contact"));
if (value != null)
this.ContactID = value.ContactID;
}
}](https://image.slidesharecdn.com/10-sessionv2-140816042452-phpapp01/85/10-Local-Database-LINQ-22-320.jpg)
10.Local Database & LINQ
- 1. Local Database & LINQ Nguyen Tuan | Microsoft Certified Trainer
- 2. Agenda Database Support in Windows Phone OS LINQ to SQL Queries Inserts, updates, deletes… Database schema upgrades Performance and best practices
- 3. LINQ to SQL
- 4. Locations where apps can access data Installation Folder App data FoldersApp data FoldersApp data Folders Credential Locker
- 6. Complex Schema • Numerous relationships and constraints • Example: Shopping List • 7 tables • 100s of records • 5 foreign keys ItemReferenceData PK ItemId ItemName ItemDescription FK1 CategoryId Categories PK CategoryId CategoryName Lists PK ListId ListName ListItems PK ListItemId ListItemName FK1 ListId Quantity Category Description FK2 StoreId Stores PK StoreId StoreName StoreLocationLat StoreLocationLong StoreAddressLine1 StoreAddressLine2 StoreAddressCity StoreAddressState StoreAddressCountry StoryAddressZip Favorites PK FavoriteItemId FavoriteItemName FavoriteItemCategory FavoriteItemQuantity FavoriteItemDescription FK1 FavoriteItemListId FavoriteItemPhoto History PK HistoryItemId HistoryItemName HistoryItemCategory HistoryItemQuantity HistoryItemDescriptioin HistoryItemDateAdded FK1 HistoryItemListId HistoryItemPhoto
- 7. Reference Data • Huge amounts of static reference data • Example: dictionary app • 3 tables • 1 table with 500k rows Words PK WordId Word Pronunciation Definition AlternateSpellings Origin Favorites PK FavoriteId FK1 WordId History PK HistoryItemId FK1 WordId AddedDate
- 8. Web Service Cache • Fetch reference data from cloud • Cache locally • Combine with user-specific data Cloud Service Windows Phone
- 9. Local Data Storage: Overview Application Settings File App Application Files Package Manager App Data Folder WP7 Isolated Storage APIs Install DB Databasefile DB Database File (r/o)
- 10. Architecture Custom Data Context App Objects Identity Management Change Tracking Update Processing Object Materialization Core ADO.NET (System.Data) SQLCE ADO.NET Provider (System.Data.SqlServerCe) SQLCEDB .CallSystem.Linq.Queryable.Select( .Call System.Linq.Queryable.Where( .Constant(Table(Wines)),'(.Lambda #Lambda1)), '(.Lambda#Lambda2)).Lambda #Lambda1(db.Wines $w) { $w.Country== “USA" } .Lambda #Lambda2(w.Country$w){ $w.Name} var query = from w in db.Wines where w.Country == "USA" select w.Name; select Name from Wines where Country = "USA"
- 11. Objects, Objects, Objects… Design time Create object model: wines, varietals, vineyards, etc. Decorate objects with attributes for persistence Run time Create DataContextreference to database Translate object model into a databasefile Submit API persists changes to DB Database upgrade Create new objects to enable new features Use upgrade APIs to change DB Varietals Wines Vineyards WineMakers Wines PK WineID Name Description RetailPrice FK2 VarietalID FK1 VineyardID Vineyards PK VineyardID Name Latitude Longitude Country Varietals PK VarietalID Name Winemaker PK WinemakerID FirstName LastName
- 12. Database Creation: Example // Define the tables in the database [Table] public class Wine : INotifyPropertyChanged, INotifyPropertyChanging { private string wineID; private string name; [Column(IsPrimaryKey=true)] public string WineID { get { return wineID; } set { InvokePropertyChanging(new PropertyChangingEventArgs("WineID" )); wineID = value; InvokePropertyChanged(new PropertyChangedEventArgs("WineID")) ; } } [Column] public string Name { ... } ... } Define Tables
- 13. Database Creation: Example // Define the data context. public partial class WineDataContext : DataContext { public Table<Wine> Wines; public Table<Vineyard> Vineyards; public WineDataContext(string connection) : base(connection) { } } ... // Create the database from data context, using a connection string DataContext db = new WineDataContext("isostore:/wineDB.sdf"); if (!db.DatabaseExists()) db.CreateDatabase();
- 14. Using SQLMetal code generator tool • Use Visual Studio or SQL Server Management Studio visual designers to create a SQL Server Compact Edition 3.5 database on Dev PC • Start a Visual Studio Command Prompt • Run the SQLMetal tool to generate LINQ to SQL code file • c:>Sqlmetal /code:northwindEntities.cs /context:NorthwindDataContext /pluralize northwind.sdf • Include generated code in your Windows Phone project • Few fixes required to get it to compile
- 15. Queries: Examples // Create the database form data context, using a connection string DataContext db = new WineDataContext("isostore:/wineDB.sdf"); // Find all wines currently at home, ordered by date acquired var q = from w in db.Wines where w.Varietal.Name == “Shiraz” && w.IsAtHome == true orderby w.DateAcquired select w;
- 16. DB Name Little Penguin Varietal Pinot Noir AtHome False Name Little Penguin Varietal Pinot Noir AtHome True Inserts/Updates/Deletes • It’s all about the DataContext • Changes made against the DataContext first • Changes persisted by calling SubmitChanges() • SubmitChanges • LINQ to SQL determines change set and submits to DB Name Little Penguin Varietal Pinot Noir AtHome False Name Yellow Tail Varietal Pinot Noir AtHome True
- 17. Inserts/Updates/Deletes Insert Update Wine newWine = new Wine { WineID = “1768", Name = “Windows Phone Syrah", Description = “Bold and spicy" }; db.Wines.InsertOnSubmit(newWine) ; db.SubmitChanges(); Wine wine = (from w in db.Wines where w.WineID == “1768" select w).First(); wine.Description = “Hints of plum and melon"; db.SubmitChanges();
- 18. Inserts/Updates/Deletes Delete var vineyardsToDelete = from Vineyards v in db.Vineyards where v.Country == “Australia” select v; db.Vineyards.DeleteAllOnSubmit (vineyardsToDelete); db.SubmitChanges();
- 20. Relationships • Express one-many, one-one and many-many relationships using EntitySet<T> and EntityRef<T> columns • In the relational database, a child table has a column – the Foreign Key – that stores the unique ID of a record in the parent table Words PK WordId Word Pronunciation Definition AlternateSpellings Origin Favorites PK FavoriteId FK1 WordId History PK HistoryItemId FK1 WordId AddedDate
- 21. Example: Parent Object [Table] public class Contact : INotifyPropertyChanged, INotifyPropertyChanging { // Fields private EntitySet<Lead> leads = new EntitySet<Lead>(); [Association(Storage = "leads", OtherKey = "ContactID")] public EntitySet<Lead> Leads { get { return this.leads; } set { InvokePropertyChanging( new PropertyChangingEventArgs("Leads")); this.leads.Assign(value); InvokePropertyChanged( new PropertyChangedEventArgs("Leads")); } }
- 22. Example: Child Object [Table] [Index (Name="ContactID_Idx", Columns="ContactID", IsUnique=false)] public class Lead : INotifyPropertyChanged, INotifyPropertyChanging { private EntityRef<Contact> contact; [Column] public long ContactID {get; set; } [Association(Storage = "contact", ThisKey = "ContactID", IsForeignKey=true)] public Contact Contact { get { return this.contact.Entity; } set { InvokePropertyChanging(new PropertyChangingEventArgs("Contact")); this.contact.Entity = value; InvokePropertyChanged(new PropertyChangedEventArgs("Contact")); if (value != null) this.ContactID = value.ContactID; } }
- 23. Deletes Delete var contactsToDelete = from Contact c in db.Contacts where c.Company == “Appamundi” select c; db.Contacts.DeleteAllOnSubmit (contactsToDelete); db.SubmitChanges();
- 24. Delete Child Objects First var contactsToDelete = from Contact c in db.Contacts where c.Company == “Appamundi" select c; foreach (Contact c in contactsToDelete) { db.Leads.DeleteAllOnSubmit(c.Leads); } db.Contacts.DeleteAllOnSubmit(contactsToDelete); db.SubmitChanges();
- 25. Demo: SqlLiteWP8
- 26. Database Schema Upgrades • DatabaseSchemaUpdater allows simple upgrades on your existing DB • Supports adding • Tables • Columns • Indices • Associations/foreign keys • Schema updates are transactional
- 27. Database Schema Upgrades WineDataContext wineDC = new WineDataContext(App.WineDBConnectionString); DatabaseSchemaUpdater dsu = wineDC.CreateDatabaseSchemaUpdater(); if (dsu.DatabaseSchemaVersion == 1) { dsu.AddColumn<Wine>("BottleType"); dsu.DatabaseSchemaVersion = 2; dsu.Execute(); }
- 28. Best Practices
- 29. LINQ to SQL Performance and Best Practices • Keep change sets small • Submit early and often to avoid data loss on app termination • Use background threads • Non-trivial operations will impact app responsiveness if done on UI thread • Optimizeread-only queries • Set ObjectTrackingEnabled to minimize memory usage • Use secondary indices for properties which you query often
- 30. LINQ to SQL Performance and Best Practices • Populatelarge reference data tables in advance • Create a simple project to prepopulate data in emulator • Pull out database file using Isolated Storage explorer • Use the right tool for the job • Database for large or complex data sets • IsolatedStorageSettings or basic files for small data sets
- 31. Summary • Database Support in Windows Phone OS • LINQ to SQL • Queries • Inserts, updates, deletes… • Database schema upgrades • Performance and best practices