LINQ体验(14)——LINQ to SQL语句之存储过程

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mb60b79a6396b63 2022-02-21 17:51:07 博主文章分类：LINQ体验

文章标签 linq 存储 sql string function 文章分类 SQL Server 数据库

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]
    (@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);

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]
     -- 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);
}

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]
     -- 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）

LINQ体验(14)——LINQ to SQL语句之存储过程_linq 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）

LINQ体验(14)——LINQ to SQL语句之存储过程_linq 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);
}

4.返回顺序结果形状映射

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

LINQ体验(14)——LINQ to SQL语句之存储过程_linq 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

LINQ体验(14)——LINQ to SQL语句之存储过程_linq 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);
}

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：

LINQ体验(14)——LINQ to SQL语句之存储过程_function_09

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：

decimal? totalSales = 0;
string customerID = "ALFKI";
db.CustOrderTotal(customerID, ref totalSales);
Console.WriteLine("Total Sales for Customer '{0}' = {1:C}",
customerID, totalSales);

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。

作者：李永京（YJingLee's Blog）