存儲過程
在我們編寫程序中，往往需要一些存儲過程，在LINQ to SQL中 怎麼使用呢？也許比原來的更簡單些。下面我們以NORTHWND.MDF數據庫中自帶的 幾個存儲過程來理解一下。
1.標量返回
在數據庫中，有名為 Customers Count By Region的存儲過程。該存儲過程返回顧客所在 "WA"區域的數量。
ALTER PROCEDURE [dbo]. [NonRowset]
(@param1 NVARCHAR(15))
AS
BEGIN
SET NOCOUNT ON;
DECLARE @count int
SELECT @count = COUNT(*)FROM Customers
WHERECustomers.Region = @Param1
RETURN @count
END
我們只要把這個存儲過程拖到O/R設 計器內，它自動生成了以下代碼段：
[Function(Name = "dbo.[Customers Count By Region]")]
public int Customers_Count_By_Region([Parameter
(DbType = "NVarChar (15)")] string param1)
{
IExecuteResult result = this.ExecuteMethodCall(this,
((MethodInfo) (MethodInfo.GetCurrentMethod())), param1);
return ((int) (result.ReturnValue));
}
我們需要時，直接調用就可以了， 例如：
int count = db.CustomersCountByRegion ("WA");
Console.WriteLine(count);
語句描述：這 個實例使用存儲過程返回在“WA”地區的客戶數。
2.單一結 果集
從數據庫中返回行集合，並包含用於篩選結果的輸入參數。 當我們執行 返回行集合的存儲過程時，會用到結果類，它存儲從存儲過程中返回的結果。
下面的示例表示一個存儲過程，該存儲過程返回客戶行並使用輸入參數 來僅返回將“London”列為客戶城市的那些行的固定幾列。
ALTER PROCEDURE [dbo].[Customers By City]
-- Add the parameters for the stored procedure here
(@param1 NVARCHAR(20))
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
SELECT CustomerID, ContactName, CompanyName, City from
Customers as c where c.City=@param1
END
拖到O/R設計器內，它自動生成了以下代碼 段：
[Function(Name="dbo.[Customers By City]")]
public ISingleResult<Customers_By_CityResult> Customers_By_City(
[Parameter(DbType="NVarChar(20)")] string param1)
{
IExecuteResult result = this.ExecuteMethodCall(this, (
(MethodInfo) (MethodInfo.GetCurrentMethod())), param1);
return ((ISingleResult<Customers_By_CityResult>)
(result.ReturnValue));
}
我們用下面的代碼調用：
ISingleResult<Customers_By_CityResult> result =
db.Customers_By_City("London");
foreach (Customers_By_CityResult cust in result)
{
Console.WriteLine("CustID={0}; City={1}", cust.CustomerID,
cust.City);
}
語句描述：這 個實例使用存儲過程返回在倫敦的客戶的 CustomerID和City。
3.多個可 能形狀的單一結果集
當存儲過程可以返回多個結果形狀時，返回類型無法強 類型化為單個投影形狀。盡管 LINQ to SQL 可以生成所有可能的投影類型，但 它無法獲知將以何種順序返回它們。 ResultTypeAttribute 屬性適用於返回多 個結果類型的存儲過程，用以指定該過程可以返回的類型的集合。
在下 面的 SQL 代碼示例中，結果形狀取決於輸入（param1 = 1或param1 = 2）。我 們不知道先返回哪個投影。
ALTER PROCEDURE [dbo]. [SingleRowset_MultiShape]
-- Add the parameters for the stored procedure here
(@param1 int )
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
if(@param1 = 1)
SELECT * from Customers as c where c.Region = 'WA'
else if (@param1 = 2)
SELECT CustomerID, ContactName, CompanyName from
Customers as c where c.Region = 'WA'
END
拖到O/R 設計器內，它自動生成了以下代碼段：
[Function (Name="dbo.[Whole Or Partial Customers Set]")]
public ISingleResult<Whole_Or_Partial_Customers_SetResult>
Whole_Or_Partial_Customers_Set([Parameter(DbType="Int")]
System.Nullable<int> param1)
{
IExecuteResult result = this.ExecuteMethodCall(this,
((MethodInfo)(MethodInfo.GetCurrentMethod())), param1);
return ((ISingleResult<Whole_Or_Partial_Customers_SetResult>)
(result.ReturnValue));
}
但是，VS2008會把多結果集 存儲過程識別為單結果集的存儲過程，默認生成的代碼我們要手動修改一下，要 求返回多個結果集，像這樣：
[Function(Name="dbo.[Whole Or Partial Customers Set]")]
[ResultType(typeof (WholeCustomersSetResult))]
[ResultType(typeof (PartialCustomersSetResult))]
public IMultipleResults Whole_Or_Partial_Customers_Set([Parameter
(DbType="Int")] System.Nullable<int> param1)
{
IExecuteResult result = this.ExecuteMethodCall(this,
((MethodInfo)(MethodInfo.GetCurrentMethod())), param1);
return ((IMultipleResults)(result.ReturnValue));
}
我們 分別定義了兩個分部類，用於指定返回的類型。WholeCustomersSetResult類 如 下：
public partial class WholeCustomersSetResult
{
private string _CustomerID;
private string _CompanyName;
private string _ContactName;
private string _ContactTitle;
private string _Address;
private string _City;
private string _Region;
private string _PostalCode;
private string _Country;
private string _Phone;
private string _Fax;
public WholeCustomersSetResult()
{
}
[Column (Storage = "_CustomerID", DbType = "NChar(5)")]
public string CustomerID
{
get { return this._CustomerID; }
set
{
if ((this._CustomerID != value))
this._CustomerID = value;
}
}
[Column(Storage = "_CompanyName", DbType = "NVarChar(40)")]
public string CompanyName
{
get { return this._CompanyName; }
set
{
if ((this._CompanyName != value))
this._CompanyName = value;
}
}
[Column (Storage = "_ContactName", DbType = "NVarChar(30) ")]
public string ContactName
{
get { return this._ContactName; }
set
{
if ((this._ContactName != value))
this._ContactName = value;
}
}
[Column (Storage = "_ContactTitle", DbType = "NVarChar(30) ")]
public string ContactTitle
{
get { return this._ContactTitle; }
set
{
if ((this._ContactTitle != value))
this._ContactTitle = value;
}
}
[Column(Storage = "_Address", DbType = "NVarChar(60) ")]
public string Address
{
get { return this._Address; }
set
{
if ((this._Address != value))
this._Address = value;
}
}
[Column(Storage = "_City", DbType = "NVarChar(15)")]
public string City
{
get { return this._City; }
set
{
if ((this._City != value))
this._City = value;
}
}
[Column(Storage = "_Region", DbType = "NVarChar (15)")]
public string Region
{
get { return this._Region; }
set
{
if ((this._Region != value))
this._Region = value;
}
}
[Column(Storage = "_PostalCode", DbType = "NVarChar(10)")]
public string PostalCode
{
get { return this._PostalCode; }
set
{
if ((this._PostalCode != value))
this._PostalCode = value;
}
}
[Column(Storage = "_Country", DbType = "NVarChar(15)")]
public string Country
{
get { return this._Country; }
set
{
if ((this._Country != value))
this._Country = value;
}
}
[Column(Storage = "_Phone", DbType = "NVarChar(24)")]
public string Phone
{
get { return this._Phone; }
set
{
if ((this._Phone != value))
this._Phone = value;
}
}
[Column(Storage = "_Fax", DbType = "NVarChar(24)")]
public string Fax
{
get { return this._Fax; }
set
{
if ((this._Fax != value))
this._Fax = value;
}
}
}
PartialCustomersSetResult類 如下：
public partial class PartialCustomersSetResult
{
private string _CustomerID;
private string _ContactName;
private string _CompanyName;
public PartialCustomersSetResult()
{
}
[Column (Storage = "_CustomerID", DbType = "NChar(5)")]
public string CustomerID
{
get { return this._CustomerID; }
set
{
if ((this._CustomerID != value))
this._CustomerID = value;
}
}
[Column(Storage = "_ContactName", DbType = "NVarChar(30)")]
public string ContactName
{
get { return this._ContactName; }
set
{
if ((this._ContactName != value))
this._ContactName = value;
}
}
[Column (Storage = "_CompanyName", DbType = "NVarChar(40) ")]
public string CompanyName
{
get { return this._CompanyName; }
set
{
if ((this._CompanyName != value))
this._CompanyName = value;
}
}
}
這樣就可以使用了，下面代碼直接調用，分別返回各自的結果集 合。
//返回全部Customer結果集
IMultipleResults result = db.Whole_Or_Partial_Customers_Set(1);
IEnumerable<WholeCustomersSetResult> shape1 =
result.GetResult<WholeCustomersSetResult>();
foreach (WholeCustomersSetResult compName in shape1)
{
Console.WriteLine(compName.CompanyName);
}
//返回部分 Customer結果集
result = db.Whole_Or_Partial_Customers_Set(2);
IEnumerable<PartialCustomersSetResult> shape2 =
result.GetResult<PartialCustomersSetResult>();
foreach (PartialCustomersSetResult con in shape2)
{
Console.WriteLine(con.ContactName);
}
語句描述：這個實例 使用存儲過程返回“WA”地區中的一組客戶。返回的結果集形狀取決 於傳入的參數。如果參數等於 1，則返回所有客戶屬性。如果參數等於2，則返 回ContactName屬性。
4.多個結果集
這種存儲過程可以生成多個結果 形狀，但我們已經知道結果的返回順序。
下面是一個按順序返回多個結 果集的存儲過程Get Customer And Orders。 返回顧客ID為"SEVES" 的顧客和他們所有的訂單。
ALTER PROCEDURE [dbo].[Get Customer And Orders]
(@CustomerID nchar(5))
-- Add the parameters for the stored procedure here
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
SELECT * FROM Customers AS c WHERE c.CustomerID = @CustomerID
SELECT * FROM Orders AS o WHERE o.CustomerID = @CustomerID
END
拖到設計器代碼如下：
[Function (Name="dbo.[Get Customer And Orders]")]
public ISingleResult<Get_Customer_And_OrdersResult>
Get_Customer_And_Orders([Parameter(Name="CustomerID",
DbType="NChar(5)")] string customerID)
{
IExecuteResult result = this.ExecuteMethodCall(this,
((MethodInfo)(MethodInfo.GetCurrentMethod())), customerID);
return ((ISingleResult<Get_Customer_And_OrdersResult>)
(result.ReturnValue));
}
同樣，我們要修改自動生成的代碼 ：
[Function(Name="dbo.[Get Customer And Orders] ")]
[ResultType(typeof(CustomerResultSet))]
[ResultType(typeof(OrdersResultSet))]
public IMultipleResults Get_Customer_And_Orders
([Parameter (Name="CustomerID",DbType="NChar(5)")]
string customerID)
{
IExecuteResult result = this.ExecuteMethodCall(this,
((MethodInfo) (MethodInfo.GetCurrentMethod())), customerID);
return ((IMultipleResults)(result.ReturnValue));
}
同樣，自己手 寫類，讓其存儲過程返回各自的結果集。
CustomerResultSet類
public partial class CustomerResultSet
{
private string _CustomerID;
private string _CompanyName;
private string _ContactName;
private string _ContactTitle;
private string _Address;
private string _City;
private string _Region;
private string _PostalCode;
private string _Country;
private string _Phone;
private string _Fax;
public CustomerResultSet()
{
}
[Column(Storage = "_CustomerID", DbType = "NChar(5)")]
public string CustomerID
{
get { return this._CustomerID; }
set
{
if ((this._CustomerID != value))
this._CustomerID = value;
}
}
[Column(Storage = "_CompanyName", DbType = "NVarChar(40)")]
public string CompanyName
{
get { return this._CompanyName; }
set
{
if ((this._CompanyName != value))
this._CompanyName = value;
}
}
[Column (Storage = "_ContactName", DbType = "NVarChar(30) ")]
public string ContactName
{
get { return this._ContactName; }
set
{
if ((this._ContactName != value))
this._ContactName = value;
}
}
[Column (Storage = "_ContactTitle", DbType = "NVarChar(30) ")]
public string ContactTitle
{
get { return this._ContactTitle; }
set
{
if ((this._ContactTitle != value))
this._ContactTitle = value;
}
}
[Column(Storage = "_Address", DbType = "NVarChar(60) ")]
public string Address
{
get { return this._Address; }
set
{
if ((this._Address != value))
this._Address = value;
}
}
[Column(Storage = "_City", DbType = "NVarChar(15)")]
public string City
{
get { return this._City; }
set
{
if ((this._City != value))
this._City = value;
}
}
[Column(Storage = "_Region", DbType = "NVarChar (15)")]
public string Region
{
get { return this._Region; }
set
{
if ((this._Region != value))
this._Region = value;
}
}
[Column(Storage = "_PostalCode", DbType = "NVarChar(10)")]
public string PostalCode
{
get { return this._PostalCode; }
set
{
if ((this._PostalCode != value))
this._PostalCode = value;
}
}
[Column(Storage = "_Country", DbType = "NVarChar(15)")]
public string Country
{
get { return this._Country; }
set
{
if ((this._Country != value))
this._Country = value;
}
}
[Column(Storage = "_Phone", DbType = "NVarChar(24)")]
public string Phone
{
get { return this._Phone; }
set
{
if ((this._Phone != value))
this._Phone = value;
}
}
[Column(Storage = "_Fax", DbType = "NVarChar(24)")]
public string Fax
{
get { return this._Fax; }
set
{
if ((this._Fax != value))
this._Fax = value;
}
}
}
OrdersResultSet 類
public partial class OrdersResultSet
{
private System.Nullable<int> _OrderID;
private string _CustomerID;
private System.Nullable<int> _EmployeeID;
private System.Nullable<System.DateTime> _OrderDate;
private System.Nullable<System.DateTime> _RequiredDate;
private System.Nullable<System.DateTime> _ShippedDate;
private System.Nullable<int> _ShipVia;
private System.Nullable<decimal> _Freight;
private string _ShipName;
private string _ShipAddress;
private string _ShipCity;
private string _ShipRegion;
private string _ShipPostalCode;
private string _ShipCountry;
public OrdersResultSet()
{
}
[Column(Storage = "_OrderID", DbType = "Int")]
public System.Nullable<int> OrderID
{
get { return this._OrderID; }
set
{
if ((this._OrderID != value))
this._OrderID = value;
}
}
[Column(Storage = "_CustomerID", DbType = "NChar(5)")]
public string CustomerID
{
get { return this._CustomerID; }
set
{
if ((this._CustomerID != value))
this._CustomerID = value;
}
}
[Column(Storage = "_EmployeeID", DbType = "Int")]
public System.Nullable<int> EmployeeID
{
get { return this._EmployeeID; }
set
{
if ((this._EmployeeID != value))
this._EmployeeID = value;
}
}
[Column(Storage = "_OrderDate", DbType = "DateTime")]
public System.Nullable<System.DateTime> OrderDate
{
get { return this._OrderDate; }
set
{
if ((this._OrderDate != value))
this._OrderDate = value;
}
}
[Column (Storage = "_RequiredDate", DbType = "DateTime")]
public System.Nullable<System.DateTime> RequiredDate
{
get { return this._RequiredDate; }
set
{
if ((this._RequiredDate != value))
this._RequiredDate = value;
}
}
[Column(Storage = "_ShippedDate", DbType = "DateTime")]
public System.Nullable<System.DateTime> ShippedDate
{
get { return this._ShippedDate; }
set
{
if ((this._ShippedDate != value))
this._ShippedDate = value;
}
}
[Column(Storage = "_ShipVia", DbType = "Int")]
public System.Nullable<int> ShipVia
{
get { return this._ShipVia; }
set
{
if ((this._ShipVia != value))
this._ShipVia = value;
}
}
[Column (Storage = "_Freight", DbType = "Money")]
public System.Nullable<decimal> Freight
{
get { return this._Freight; }
set
{
if ((this._Freight != value))
this._Freight = value;
}
}
[Column (Storage = "_ShipName", DbType = "NVarChar(40)")]
public string ShipName
{
get { return this._ShipName; }
set
{
if ((this._ShipName != value))
this._ShipName = value;
}
}
[Column(Storage = "_ShipAddress", DbType = "NVarChar(60)")]
public string ShipAddress
{
get { return this._ShipAddress; }
set
{
if ((this._ShipAddress != value))
this._ShipAddress = value;
}
}
[Column (Storage = "_ShipCity", DbType = "NVarChar(15)")]
public string ShipCity
{
get { return this._ShipCity; }
set
{
if ((this._ShipCity != value))
this._ShipCity = value;
}
}
[Column(Storage = "_ShipRegion", DbType = "NVarChar(15)")]
public string ShipRegion
{
get { return this._ShipRegion; }
set
{
if ((this._ShipRegion != value))
this._ShipRegion = value;
}
}
[Column(Storage = "_ShipPostalCode", DbType = "NVarChar(10)")]
public string ShipPostalCode
{
get { return this._ShipPostalCode; }
set
{
if ((this._ShipPostalCode != value))
this._ShipPostalCode = value;
}
}
[Column(Storage = "_ShipCountry", DbType = "NVarChar (15)")]
public string ShipCountry
{
get { return this._ShipCountry; }
set
{
if ((this._ShipCountry != value))
this._ShipCountry = value;
}
}
}
這時，只要調用就可以了。
IMultipleResults result = db.Get_Customer_And_Orders("SEVES");
//返回 Customer結果集
IEnumerable<CustomerResultSet> customer =
result.GetResult<CustomerResultSet>();
//返回Orders結果集
IEnumerable<OrdersResultSet> orders =
result.GetResult<OrdersResultSet>();
//在這裡，我們讀取 CustomerResultSet中的數據
foreach (CustomerResultSet cust in customer)
{
Console.WriteLine(cust.CustomerID);
}
語句描述：這個實例使用存儲過程返回客戶“SEVES”及 其所有訂單。
5.帶輸出參數
LINQ to SQL 將輸出參數映射到引用參數 ，並且對於值類型，它將參數聲明為可以為 null。
下面的示例帶有單 個輸入參數（客戶 ID）並返回一個輸出參數（該客戶的總銷售額）。
ALTER PROCEDURE [dbo].[CustOrderTotal]
@CustomerID nchar(5),
@TotalSales money OUTPUT
AS
SELECT @TotalSales = SUM(OD.UNITPRICE*(1-OD.DISCOUNT) * OD.QUANTITY)
FROM ORDERS O, "ORDER DETAILS" OD
where O.CUSTOMERID = @CustomerID AND O.ORDERID = OD.ORDERID
把這個存儲過程拖到設 計器中，圖片如下：
其生成代碼如下：
[Function (Name="dbo.CustOrderTotal")]
public int CustOrderTotal (
[Parameter(Name="CustomerID", DbType="NChar(5) ")]string customerID,
[Parameter (Name="TotalSales", DbType="Money")]
ref System.Nullable<decimal> totalSales)
{
IExecuteResult result = this.ExecuteMethodCall(this,
((MethodInfo)(MethodInfo.GetCurrentMethod())),
customerID, totalSales);
totalSales = ((System.Nullable<decimal>)
(result.GetParameterValue(1)));
return ((int) (result.ReturnValue));
}
我們使用下面的語句調用此存儲過 程：注意：輸出參數是按引用傳遞的，以支持參數為“in/out”的方 案。在這種情況下，參數僅為“out”。
decimal? totalSales = 0;
string customerID = "ALFKI";
db.CustOrderTotal(customerID, ref totalSales);
Console.WriteLine("Total Sales for Customer '{0}' = {1:C}",
customerID, totalSales);
語句描述：這個實例 使用返回 Out 參數的存儲過程。
好了，就說到這裡了，其增刪改操作同 理。相信大家通過這5個實例理解了存儲過程。
