深度剖析LINQtoSQL存储过程
本文将从5个方面来学习LINQ to SQL存储过程，它们其中有LINQ to SQL存储过程之标量返回、LINQ to SQL存储过程之单一结果集等等。
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在我们编写程序中，往往需要一些存储过程，LINQ to SQL存储过程中怎么使用呢？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.LINQ to SQL存储过程之标量返回
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.LINQ to SQL存储过程之单一结果集
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_City(
- [Parameter(DbType="NVarChar(20)")] string param1)
- {
- IExecuteResult result = this.ExecuteMethodCall(this, (
- (MethodInfo)(MethodInfo.GetCurrentMethod())), param1);
- return ((ISingleResult )
- (result.ReturnValue));
- }
我们用下面的代码调用：
- ISingleResult 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.LINQ to SQL存储过程之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_Set([Parameter(DbType="Int")]
- System.Nullable
param1) - {
- IExecuteResult result = this.ExecuteMethodCall(this,
- ((MethodInfo)(MethodInfo.GetCurrentMethod())), param1);
- return ((ISingleResult )
- (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
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 shape1 =
- result.GetResult ();
- 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 shape2 =
- result.GetResult ();
- 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.LINQ to SQL存储过程之多个结果集
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_Orders([Parameter(Name="CustomerID",
- DbType="NChar(5)")] string customerID)
- {
- IExecuteResult result = this.ExecuteMethodCall(this,
- ((MethodInfo)(MethodInfo.GetCurrentMethod())), customerID);
- return ((ISingleResult )
- (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
_OrderID; - private string _CustomerID;
- private System.Nullable
_EmployeeID; - private System.Nullable _OrderDate;
- private System.Nullable _RequiredDate;
- private System.Nullable _ShippedDate;
- private System.Nullable
_ShipVia; - private System.Nullable
_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
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
EmployeeID - {
- get { return this._EmployeeID; }
- set
- {
- if ((this._EmployeeID != value))
- this._EmployeeID = value;
- }
- }
- [Column(Storage = "_OrderDate", DbType = "DateTime")]
- public System.Nullable OrderDate
- {
- get { return this._OrderDate; }
- set
- {
- if ((this._OrderDate != value))
- this._OrderDate = value;
- }
- }
- [Column(Storage = "_RequiredDate", DbType = "DateTime")]
- public System.Nullable RequiredDate
- &
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