在咱們編寫程序中,每每須要一些存儲過程,在LINQ to SQL中怎麼使用呢?也許比原來的更簡單些。下面咱們以NORTHWND.MDF數據庫中自帶的幾個存儲過程來理解一下。數據庫
在數據庫中,有名爲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。this
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
咱們只要把這個存儲過程拖到O/R設計器內,它自動生成了如下代碼段:spa
[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)); }
咱們須要時,直接調用就能夠了,例如:設計
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。code
從數據庫中返回行集合,幷包含用於篩選結果的輸入參數。 當咱們執行返回行集合的存儲過程時,會用到結果類,它存儲從存儲過程當中返回的結果。blog
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」列爲客戶城市的那些行的固定幾列。 ip
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,它自動生成了如下代碼段:ci
[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)); }
咱們用下面的代碼調用:string
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。 it
當存儲過程能夠返回多個結果形狀時,返回類型沒法強類型化爲單個投影形狀。儘管 LINQ to SQL 能夠生成全部可能的投影類型,但它沒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,用以指定該過程能夠返回的類型的集合。
在下面的 SQL 代碼示例中,結果形狀取決於輸入(param1 = 1或param1 = 2)。咱們不知道先返回哪一個投影。
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,它自動生成了如下代碼段:
[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)); }
可是,VS2008會把多結果集存儲過程識別爲單結果集的存儲過程,默認生成的代碼咱們要手動修改一下,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)); }
咱們分別定義了兩個分部類,用於指定返回的類型。WholeCustomersSetResult類 以下:
這樣就可使用了,下面代碼直接調用,分別返回各自的結果集合。
//返回所有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。若是參數等於 1,則返回全部客戶屬性。若是參數等於2,則返回ContactName屬性。
這種存儲過程能夠生成多個結果形狀,但咱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爲"SEVES"的顧客和他們全部的訂單。
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
拖到設計器代碼以下:
[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)); }
一樣,咱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)); }
一樣,本身手寫類,讓其存儲過程返回各自的結果集。
CustomerResultSet類
OrdersResultSet類
這時,只要調用就能夠了。
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>(); //在這裏,咱們讀取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」及其全部訂單。
LINQ to SQL 將輸出參數映射到引用參數,而且對於值類型,它將參數聲明爲能夠爲 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
其生成代碼以下:
[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)); }
咱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,以支持參數爲「in/out」的方案。在這種狀況下,參數僅爲「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,就說到這裏了,其增刪改操做同理。相信你們經過這5個實例理解了存儲過程。
文章很好,看看都想轉載,因而轉了!感謝您的耐心閱讀。