LINQ to SQL存储过程是怎样的

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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      {          get { return this._RequiredDate; }          set         {              if ((this._RequiredDate != value))                  this._RequiredDate = value;          }      }      [Column(Storage = "_ShippedDate", DbType = "DateTime")]      public System.Nullable ShippedDate      {          get { return this._ShippedDate; }          set         {              if ((this._ShippedDate != value))                  this._ShippedDate = value;          }      }      [Column(Storage = "_ShipVia", DbType = "Int")]      public System.Nullable ShipVia      {          get { return this._ShipVia; }          set         {              if ((this._ShipVia != value))                  this._ShipVia = value;          }      }      [Column(Storage = "_Freight", DbType = "Money")]      public System.Nullable 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 customer =   result.GetResult();  //返回Orders结果集  IEnumerable orders =    result.GetResult();  //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.LINQ to SQL存储过程之带输出参数

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，

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 totalSales)  {      IExecuteResult result = this.ExecuteMethodCall(this,      ((MethodInfo)(MethodInfo.GetCurrentMethod())),      customerID, totalSales);      totalSales = ((System.Nullable)      (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。

感谢各位的阅读，以上就是"LINQ to SQL存储过程是怎样的"的内容了，经过本文的学习后，相信大家对LINQ to SQL存储过程是怎样的这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是，小编将为大家推送更多相关知识点的文章，欢迎关注！