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.返回数量

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]
\n    (@param1 NVARCHAR(15))
\nAS
\nBEGIN
\n    SET NOCOUNT ON;
\n     DECLARE @count int
\n     SELECT @count = COUNT(*)FROM Customers
\n     WHERECustomers.Region = @Param1
\n     RETURN @count
\nEND

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]“)]
\npublic int Customers_Count_By_Region([Parameter
\n(DbType="NVarChar(15)")] string param1)
\n{
\n     IExecuteResult result = this.ExecuteMethodCall(this,
\n     ((MethodInfo)(MethodInfo.GetCurrentMethod())), param1);
\n     return ((int)(result.ReturnValue));
\n}

我们需要时，直接调用就可以了，例如：

int count = db.CustomersCountByRegion(“WA”);
\nConsole.WriteLine(count);

2.返回行集合

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]
\n     — Add the parameters for the stored procedure here
\n     (@param1 NVARCHAR(20))
\nAS
\nBEGIN
\n     — SET NOCOUNT ON added to prevent extra result sets from
\n     — interfering with SELECT statements.
\n     SET NOCOUNT ON;
\n     SELECT CustomerID, ContactName, CompanyName, City from
\n     Customers as c where c.City=@param1
\nEND

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]“)]
\npublic ISingleResult<Customers_By_CityResult> Customers_By_City(
\n[Parameter(DbType="NVarChar(20)")] string param1)
\n{
\n     IExecuteResult result = this.ExecuteMethodCall(this, (
\n     (MethodInfo)(MethodInfo.GetCurrentMethod())), param1);
\n     return ((ISingleResult<Customers_By_CityResult>)
\n     (result.ReturnValue));
\n}

我们用下面的代码调用：

ISingleResult<Customers_By_CityResult> result =
\ndb.Customers_By_City(“London”);
\nforeach (Customers_By_CityResult cust in result)
\n{
\n     Console.WriteLine(“CustID={0}; City={1}”, cust.CustomerID,
\n         cust.City);
\n}

3.返回多个结果形状的映射

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]
\n     — Add the parameters for the stored procedure here
\n     (@param1 int )
\nAS
\nBEGIN
\n     — SET NOCOUNT ON added to prevent extra result sets from
\n     — interfering with SELECT statements.
\n     SET NOCOUNT ON;
\n     if(@param1 = 1)
\n     SELECT * from Customers as c where c.Region = ‘WA’
\n     else if (@param1 = 2)
\n     SELECT CustomerID, ContactName, CompanyName from
\n     Customers as c where c.Region = ‘WA’
\nEND

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]“)]
\npublic ISingleResult<Whole_Or_Partial_Customers_SetResult>
\nWhole_Or_Partial_Customers_Set([Parameter(DbType="Int")]
\nSystem.Nullable<int> param1)
\n{
\n     IExecuteResult result = this.ExecuteMethodCall(this,
\n     ((MethodInfo)(MethodInfo.GetCurrentMethod())), param1);
\n     return ((ISingleResult<Whole_Or_Partial_Customers_SetResult>)
\n     (result.ReturnValue));
\n}

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]“)]
\n[ResultType(typeof(WholeCustomersSetResult))]
\n[ResultType(typeof(PartialCustomersSetResult))]
\npublic IMultipleResults Whole_Or_Partial_Customers_Set([Parameter
\n(DbType="Int")] System.Nullable<int> param1)
\n{
\n     IExecuteResult result = this.ExecuteMethodCall(this,
\n     ((MethodInfo)(MethodInfo.GetCurrentMethod())), param1);
\n     return ((IMultipleResults)(result.ReturnValue));
\n}

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：

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：

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);
}

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形状的存储过程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);
}

ALTER PROCEDURE [dbo].[CustOrderTotal]
\n@CustomerID nchar(5),
\n@TotalSales money OUTPUT
\nAS
\nSELECT @TotalSales = SUM(OD.UNITPRICE*(1-OD.DISCOUNT) * OD.QUANTITY)
\nFROM ORDERS O, “ORDER DETAILS” OD
\nwhere O.CUSTOMERID = @CustomerID AND O.ORDERID = OD.ORDERID

[Function(Name="dbo.CustOrderTotal")]
\npublic int CustOrderTotal([Parameter(Name="CustomerID", DbType="NChar(5)")]
\nstring customerID,[Parameter(Name="TotalSales", DbType="Money")]
\nref System.Nullable<decimal> totalSales)
\n{
\n     IExecuteResult result = this.ExecuteMethodCall(this, ((MethodInfo)
\n     (MethodInfo.GetCurrentMethod())), customerID, totalSales);
\n     totalSales = ((System.Nullable<decimal>)(result.GetParameterValue(1)));
\n     return ((int)(result.ReturnValue));
\n}

decimal? totalSales = 0;
\nstring customerID = “ALFKI”;
\ndb.CustOrderTotal(customerID, ref totalSales);
\nConsole.WriteLine(“Total Sales for Customer ‘{0}’ = {1:C}”,
\ncustomerID, totalSales);