在五月份这个版本里，DLINQ提供了下面这些新功能(详情参考《DLinq Overview for CSharp Developers.doc》第七章“New Features in May 2006 Preview”)
1。支持继承，目前只支持单表继承
2。对多层应用的支持，DataContext对象多了一个Attach()方法，可在不同层或不同请求中更新实体对象
3。对远程和本地实体集合的支持。实体集合实现了IQueryable<T> ，确保过滤性查询在数据库端完成
4。支持Join，这样你能做这样的查询
var q = from s in db.Suppliers
join c in db.Customers on s.City equals c.City
select new {
Supplier = s.CompanyName,
Customer = c.CompanyName,
City = c.City
};
5。对外部XML映射文件的支持
编码调用
String path = @”C:\Mapping\NorthwindMapping.xml”;
XmlMappingSource prodMapping =
XmlMappingSource.FromXml(File.ReadAllText(path));
Northwind db = new Northwind(
@”Server=.\SQLExpress;Database=c:\Northwind\Northwnd.mdf”,
prodMapping
);
映射文件
<Database Name=”Northwind”>
<Table Name=”Products“>
<Type Name=”Mapping.Product“>
<Column Name=”ProductID” Member=”ProductID” Storage=”_ProductID”
DbType=”Int NOT NULL IDENTITY” IsIdentity=”True”
IsAutoGen=”True” />
<Column Name=”ProductName” Member=”ProductName”
Storage=”_ProductName” DbType=”NVarChar(40) NOT NULL” />
<Column Name=”SupplierID” Member=”SupplierID” Storage=”_SupplierID”
DbType=”Int” />
…..
<Association Name=”FK_Order_Details_Products” Member=”OrderDetails”
Storage=”_OrderDetails” ThisKey=”ProductID”
OtherTable=”Order Details” OtherKey=”ProductID” />
<Association Name=”FK_Products_Categories” Member=”Category”
…..
</Type>
</Table>
<Table Name=”Order Details”>
<Type Name=”Mapping.OrderDetail”>
…..
</Type>
</Table>
…
</Database>
6。对存储过程以及自定义函数的支持
存储过程:
CREATE PROCEDURE GetCustomerOrderCount(@CustomerID nchar(5))
AS
Declare @count int
SELECT @count = COUNT(*) FROM ORDERS WHERE CustomerID = @CustomerID
RETURN @count
映射方法:
[StoredProcedure(Name=”GetCustomerOrderCount”)]
public int GetCustomerOrderCount(
[Parameter(Name=”CustomerID”)] string customerID
)
{
StoredProcedureResult result = this.ExecuteStoredProcedure(
((MethodInfo)(MethodInfo.GetCurrentMethod())), customerID);
return result.ReturnValue.Value;
}
7。提供了一个DLinq Query Visualizer，在调试时查看实际SQL语句以及参数情形
8。新添加了一个设计器，用于设计类(表)间关系以及生成编码
在项目里添加一个DLinqObjects模块，然后把Northwind数据库里的2个类Customers和Orders两个表先后拖到DLinq设计器上，设计器会根据数据库里的关系自动建立关联，同时生成下列编码
namespace LINQConsoleApplication1 {
public partial class NorthwindDataContext : System.Data.DLinq.DataContext {
public System.Data.DLinq.Table<Customer> Customers;
public System.Data.DLinq.Table<Order> Orders;
…..
[System.Data.DLinq.Table(Name=”Customers”)]
public partial class Customer : System.Data.DLinq.INotifyPropertyChanging,
System.ComponentModel.INotifyPropertyChanged {
private string _CustomerID;
…..
private System.Data.DLinq.EntitySet<Order> _Orders;
…..
[System.Diagnostics.DebuggerNonUserCodeAttribute()]
[System.Data.DLinq.Association(Name=”FK_Orders_Customers”, Storage=”_Orders”, OtherKey=”CustomerID”)]
public virtual System.Data.DLinq.EntitySet<Order> Orders {
get {
return this._Orders;
}
set {
this._Orders.Assign(value);
}
}
…..
}
[System.Data.DLinq.Table(Name=”Orders”)]
public partial class Order : System.Data.DLinq.INotifyPropertyChanging, System.ComponentModel.INotifyPropertyChanged
{
private int _OrderID;
…..
private System.Data.DLinq.EntityRef<Customer> _Customer;
…..
[System.Diagnostics.DebuggerNonUserCodeAttribute()]
[System.Data.DLinq.Association(Name=”FK_Orders_Customers”, Storage=”_Customer”, ThisKey=”CustomerID”,
IsParent=true)]
public Customer Customer {
get {
return this._Customer.Entity;
}
set {
if ((this._Customer.Entity != value)) {
this.OnPropertyChanging(“Customer”);
if ((this._Customer.Entity != null)) {
this._Customer.Entity = null;
this._Customer.Entity.Orders.Remove(this);
}
this._Customer.Entity = value;
if ((value != null)) {
value.Orders.Add(this);
}
this.OnPropertyChanged(“Customer”);
}
}
}
…..
}
假设你有类似这样的数据表Person，当Type为2时表明是Employee
| 字段名 |
数据类型 |
允许空 |
| Type |
int |
True |
| ID(主键) |
int |
False |
| FirstName |
nvarchar(200) |
False |
| LastName |
nvarchar(200) |
False |
| Manager |
int |
True |
拖动2份Person到设计器，把第二份改名为Employee
把Manager属性从Person类删去，从Employee类，保持Manager属性，删去其他的属性，从工具箱里选择“继承”连接，然后依次选择Employee类，Person类，建立继承关系
设置DiscriminatorColumn为Type，把Employee的DiscriminatorValue设置为2，把Person的DiscriminatorValue设置为1，保存后，会生成下列编码
[System.Data.DLinq.InheritanceMapping(Code=1, Type=typeof(Person), IsDefault=true)]
[System.Data.DLinq.InheritanceMapping(Code=2, Type=typeof(Employee))]
[System.Data.DLinq.Table(Name=”Person”)]
public partial class Person : System.Data.DLinq.INotifyPropertyChanging, System.ComponentModel.INotifyPropertyChanged {
…..
}
public partial class Employee : Person {
private System.Nullable<int> _Manager;
…..
}
}
