存储过程
在我们编写程序中，往往需要一些存储过程，在LINQ to SQL中怎么使用呢？也许比原来的更简单些。下面我们以NORTHWND.MDF数据库中自带的几个存储过程来理解一下。
1.标量返回
在数据库中，有名为Customers Count By Region的存储过程。该存储过程返回顾客所在"WA"区域的数量。
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
我们只要把这个存储过程拖到O/R设计器内，它自动生成了以下代码段：
[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)); }
我们需要时，直接调用就可以了，例如：
int count = db.CustomersCountByRegion("WA"); Console.WriteLine(count);
语句描述：这个实例使用存储过程返回在“WA”地区的客户数。
2.单一结果集
从数据库中返回行集合，并包含用于筛选结果的输入参数。 当我们执行返回行集合的存储过程时，会用到结果类，它存储从存储过程中返回的结果。
下面的示例表示一个存储过程，该存储过程返回客户行并使用输入参数来仅返回将“London”列为客户城市的那些行的固定几列。
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设计器内，它自动生成了以下代码段：
[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)); }
我们用下面的代码调用：
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); }
语句描述：这个实例使用存储过程返回在伦敦的客户的 CustomerID和City。
3.多个可能形状的单一结果集
当存储过程可以返回多个结果形状时，返回类型无法强类型化为单个投影形状。尽管 LINQ to SQL 可以生成所有可能的投影类型，但它无法获知将以何种顺序返回它们。 ResultTypeAttribute 属性适用于返回多个结果类型的存储过程，用以指定该过程可以返回的类型的集合。
在下面的 SQL 代码示例中，结果形状取决于输入（param1 = 1或param1 = 2）。我们不知道先返回哪个投影。
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设计器内，它自动生成了以下代码段：
[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会把多结果集存储过程识别为单结果集的存储过程，默认生成的代码我们要手动修改一下，要求返回多个结果集，像这样：
[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)); }
我们分别定义了两个分部类，用于指定返回的类型。WholeCustomersSetResult类 如下：（点击展开）
代码在这里展开
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类 如下：（点击展开）
代码在这里展开
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; } } }
这样就可以使用了，下面代码直接调用，分别返回各自的结果集合。
//返回全部Customer结果集 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结果集 result = db.Whole_Or_Partial_Customers_Set(2); IEnumerable<PartialCustomersSetResult> shape2 = result.GetResult<PartialCustomersSetResult>(); foreach (PartialCustomersSetResult con in shape2) { Console.WriteLine(con.ContactName); }
语句描述：这个实例使用存储过程返回“WA”地区中的一组客户。返回的结果集形状取决于传入的参数。如果参数等于 1，则返回所有客户属性。如果参数等于 2，则返回ContactName属性。
4.多个结果集
这种存储过程可以生成多个结果形状，但我们已经知道结果的返回顺序。
下面是一个按顺序返回多个结果集的存储过程Get Customer And Orders。 返回顾客ID为"SEVES"的顾客和他们所有的订单。
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
拖到设计器代码如下：
[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)); }
同样，我们要修改自动生成的代码：
[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)); }
同样，自己手写类，让其存储过程返回各自的结果集。
CustomerResultSet类
代码在这里展开
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类
代码在这里展开
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; } } }
这时，只要调用就可以了。
IMultipleResults result = db.Get_Customer_And_Orders("SEVES"); //返回Customer结果集 IEnumerable<CustomerResultSet> customer = result.GetResult<CustomerResultSet>(); //返回Orders结果集 IEnumerable<OrdersResultSet> orders = result.GetResult<OrdersResultSet>(); //在这里，我们读取CustomerResultSet中的数据 foreach (CustomerResultSet cust in customer) { Console.WriteLine(cust.CustomerID); }
语句描述：这个实例使用存储过程返回客户“SEVES”及其所有订单。
5.带输出参数
LINQ to SQL 将输出参数映射到引用参数，并且对于值类型，它将参数声明为可以为 null。
下面的示例带有单个输入参数（客户 ID）并返回一个输出参数（该客户的总销售额）。
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
把这个存储过程拖到设计器中，图片如下：
其生成代码如下：
[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)); }
我们使用下面的语句调用此存储过程：注意：输出参数是按引用传递的，以支持参数为“in/out”的方案。在这种情况下，参数仅为“out”。
decimal? totalSales = 0; string customerID = "ALFKI"; db.CustOrderTotal(customerID, ref totalSales); Console.WriteLine("Total Sales for Customer '{0}' = {1:C}", customerID, totalSales);
语句描述：这个实例使用返回 Out 参数的存储过程。
好了，就说到这里了，其增删改操作同理。相信大家通过这5个实例理解了存储过程。