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The author:(作者)归海一刀published in(发表于) 2014/1/30 1:02:47 LINQ体验(14)——LINQ,to,SQL语句之存储过程_[Asp.Net教程]
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。
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))ASBEGINSET NOCOUNT ON;DECLARE @count intSELECT @count = COUNT(*)FROM CustomersWHERECustomers.Region = @Param1RETURN @countEND
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);
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))ASBEGIN-- 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=@param1END
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);}
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 )ASBEGIN-- 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
[Function(Name="dbo.[Whole Or Partial Customers Set]")]public ISingleResultWhole_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:
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 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);}
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 hereASBEGIN -- 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 = @CustomerIDEND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);}
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 OUTPUTASSELECT @TotalSales = SUM(OD.UNITPRICE*(1-OD.DISCOUNT) * OD.QUANTITY)FROM ORDERS O, "ORDER DETAILS" ODwhere 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 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:
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)出处:http://lyj.cnblogs.com
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