08，Windows Phone 本機存放區

內容預告：

• Windows Phone 的資料庫支援
• LINQ to SQL
• 效能和最佳實務

LINQ to Everything:

支援複雜的結構：

支援外鍵：

WebService緩衝：

本機存放區：

架構：

對象：

定義表：

  // 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 { ... }      
...}

定義資料內容：

// 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 stringDataContext db = new WineDataContext("isostore:/wineDB.sdf");if (!db.DatabaseExists())     db.CreateDatabase();

用SQLMetal代碼產生工具:

c:\>Sqlmetal /code:northwindEntities.cs                   
/context:NorthwindDataContext                  
/pluralize northwind.sdf

查詢：

 // 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;

插入，更新，刪除：別忘了submitChanges

插入：

Wine newWine = new Wine{WineID = “1768",Name = “Windows Phone Syrah",Description = “Bold and spicy"};db.Wines.InsertOnSubmit(newWine);db.SubmitChanges();

更新：

Wine wine = (from w in db.Wines where w.WineID == “1768" select w).First();wine.Description = “Hints of plum and melon";db.SubmitChanges();

刪除：

var vineyardsToDelete = from Vineyards v in db.Vineyardswhere v.Country == “Australia”select v;db.Vineyards.DeleteAllOnSubmit(vineyardsToDelete);            db.SubmitChanges();

更新資料庫結構：

WineDataContext wineDC = new WineDataContext(App.WineDBConnectionString);DatabaseSchemaUpdater dsu = wineDC.CreateDatabaseSchemaUpdater();if (dsu.DatabaseSchemaVersion == 1){dsu.AddColumn<Wine>("BottleType");dsu.DatabaseSchemaVersion = 2;dsu.Execute();} 

效能和最佳實務：

• 保持修改的集合很小，換句話說，儘早提交修改，以避免程式終止時資料丟失。
• 用後台線程。
• 最佳化唯讀查詢。
• 提前填充大量資料。
• 用對的工具，大量複雜的資料用資料庫，小資料用隔離儲存區 (Isolated Storage)。