SqlCommand 类
定义
重要
一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。 对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。
表示要对 SQL Server 数据库执行的一个 Transact-SQL 语句或存储过程。 此类不能被继承。
public ref class SqlCommand sealed : System::Data::Common::DbCommand, ICloneablepublic sealed class SqlCommand : System.Data.Common.DbCommand, ICloneabletype SqlCommand = class
inherit DbCommand
interface ICloneablePublic NotInheritable Class SqlCommand
Inherits DbCommand
Implements ICloneable- 继承
-
SqlCommand
- 实现
示例
以下示例创建 SqlConnection、 SqlCommand、 和 SqlDataReader。 该示例通读数据，将其写入控制台。 最后，该示例关闭 ， SqlDataReader 然后在 SqlConnection 退出 Using 代码块时关闭 。
using System;
using System.Data;
using Microsoft.Data.SqlClient;
namespace SqlCommandCS
{
class Program
{
static void Main()
{
string str = "Data Source=(local);Initial Catalog=Northwind;"
+ "Integrated Security=SSPI";
ReadOrderData(str);
}
private static void ReadOrderData(string connectionString)
{
string queryString =
"SELECT OrderID, CustomerID FROM dbo.Orders;";
using (SqlConnection connection = new SqlConnection(
connectionString))
{
SqlCommand command = new SqlCommand(
queryString, connection);
connection.Open();
using (SqlDataReader reader = command.ExecuteReader())
{
while (reader.Read())
{
Console.WriteLine(String.Format("{0}, {1}",
reader[0], reader[1]));
}
}
}
}
以下示例演示如何创建和执行不同类型的 SqlCommand 对象。
首先，必须通过执行以下脚本来创建示例数据库：
USE [master]
GO
CREATE DATABASE [MySchool]
GO
USE [MySchool]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE procedure [dbo].[CourseExtInfo] @CourseId int
as
select c.CourseID,c.Title,c.Credits,d.Name as DepartmentName
from Course as c left outer join Department as d on c.DepartmentID=d.DepartmentID
where c.CourseID=@CourseId
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
create procedure [dbo].[DepartmentInfo] @DepartmentId int,@CourseCount int output
as
select @CourseCount=Count(c.CourseID)
from course as c
where c.DepartmentID=@DepartmentId
select d.DepartmentID,d.Name,d.Budget,d.StartDate,d.Administrator
from Department as d
where d.DepartmentID=@DepartmentId
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
Create PROCEDURE [dbo].[GetDepartmentsOfSpecifiedYear]
@Year int,@BudgetSum money output
AS
BEGIN
SELECT @BudgetSum=SUM([Budget])
FROM [MySchool].[dbo].[Department]
Where YEAR([StartDate])=@Year
SELECT [DepartmentID]
,[Name]
,[Budget]
,[StartDate]
,[Administrator]
FROM [MySchool].[dbo].[Department]
Where YEAR([StartDate])=@Year
END
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Course]([CourseID] [nvarchar](10) NOT NULL,
[Year] [smallint] NOT NULL,
[Title] [nvarchar](100) NOT NULL,
[Credits] [int] NOT NULL,
[DepartmentID] [int] NOT NULL,
CONSTRAINT [PK_Course] PRIMARY KEY CLUSTERED
(
[CourseID] ASC,
[Year] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Department]([DepartmentID] [int] IDENTITY(1,1) NOT NULL,
[Name] [nvarchar](50) NOT NULL,
[Budget] [money] NOT NULL,
[StartDate] [datetime] NOT NULL,
[Administrator] [int] NULL,
CONSTRAINT [PK_Department] PRIMARY KEY CLUSTERED
(
[DepartmentID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Person]([PersonID] [int] IDENTITY(1,1) NOT NULL,
[LastName] [nvarchar](50) NOT NULL,
[FirstName] [nvarchar](50) NOT NULL,
[HireDate] [datetime] NULL,
[EnrollmentDate] [datetime] NULL,
CONSTRAINT [PK_School.Student] PRIMARY KEY CLUSTERED
(
[PersonID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[StudentGrade]([EnrollmentID] [int] IDENTITY(1,1) NOT NULL,
[CourseID] [nvarchar](10) NOT NULL,
[StudentID] [int] NOT NULL,
[Grade] [decimal](3, 2) NOT NULL,
CONSTRAINT [PK_StudentGrade] PRIMARY KEY CLUSTERED
(
[EnrollmentID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
create view [dbo].[EnglishCourse]
as
select c.CourseID,c.Title,c.Credits,c.DepartmentID
from Course as c join Department as d on c.DepartmentID=d.DepartmentID
where d.Name=N'English'
GO
INSERT [dbo].[Course] ([CourseID], [Year], [Title], [Credits], [DepartmentID]) VALUES (N'C1045', 2012, N'Calculus', 4, 7)
INSERT [dbo].[Course] ([CourseID], [Year], [Title], [Credits], [DepartmentID]) VALUES (N'C1061', 2012, N'Physics', 4, 1)
INSERT [dbo].[Course] ([CourseID], [Year], [Title], [Credits], [DepartmentID]) VALUES (N'C2021', 2012, N'Composition', 3, 2)
INSERT [dbo].[Course] ([CourseID], [Year], [Title], [Credits], [DepartmentID]) VALUES (N'C2042', 2012, N'Literature', 4, 2)
SET IDENTITY_INSERT [dbo].[Department] ON
INSERT [dbo].[Department] ([DepartmentID], [Name], [Budget], [StartDate], [Administrator]) VALUES (1, N'Engineering', 350000.0000, CAST(0x0000999C00000000 AS DateTime), 2)
INSERT [dbo].[Department] ([DepartmentID], [Name], [Budget], [StartDate], [Administrator]) VALUES (2, N'English', 120000.0000, CAST(0x0000999C00000000 AS DateTime), 6)
INSERT [dbo].[Department] ([DepartmentID], [Name], [Budget], [StartDate], [Administrator]) VALUES (4, N'Economics', 200000.0000, CAST(0x0000999C00000000 AS DateTime), 4)
INSERT [dbo].[Department] ([DepartmentID], [Name], [Budget], [StartDate], [Administrator]) VALUES (7, N'Mathematics', 250024.0000, CAST(0x0000999C00000000 AS DateTime), 3)
SET IDENTITY_INSERT [dbo].[Department] OFF
SET IDENTITY_INSERT [dbo].[Person] ON
INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (1, N'Hu', N'Nan', NULL, CAST(0x0000A0BF00000000 AS DateTime))
INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (2, N'Norman', N'Laura', NULL, CAST(0x0000A0BF00000000 AS DateTime))
INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (3, N'Olivotto', N'Nino', NULL, CAST(0x0000A0BF00000000 AS DateTime))
INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (4, N'Anand', N'Arturo', NULL, CAST(0x0000A0BF00000000 AS DateTime))
INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (5, N'Jai', N'Damien', NULL, CAST(0x0000A0BF00000000 AS DateTime))
INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (6, N'Holt', N'Roger', CAST(0x000097F100000000 AS DateTime), NULL)
INSERT [dbo].[Person] ([PersonID], [LastName], [FirstName], [HireDate], [EnrollmentDate]) VALUES (7, N'Martin', N'Randall', CAST(0x00008B1A00000000 AS DateTime), NULL)
SET IDENTITY_INSERT [dbo].[Person] OFF
SET IDENTITY_INSERT [dbo].[StudentGrade] ON
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (1, N'C1045', 1, CAST(3.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (2, N'C1045', 2, CAST(3.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (3, N'C1045', 3, CAST(2.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (4, N'C1045', 4, CAST(4.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (5, N'C1045', 5, CAST(3.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (6, N'C1061', 1, CAST(4.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (7, N'C1061', 3, CAST(3.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (8, N'C1061', 4, CAST(2.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (9, N'C1061', 5, CAST(1.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (10, N'C2021', 1, CAST(2.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (11, N'C2021', 2, CAST(3.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (12, N'C2021', 4, CAST(3.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (13, N'C2021', 5, CAST(3.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (14, N'C2042', 1, CAST(2.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (15, N'C2042', 2, CAST(3.50 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (16, N'C2042', 3, CAST(4.00 AS Decimal(3, 2)))
INSERT [dbo].[StudentGrade] ([EnrollmentID], [CourseID], [StudentID], [Grade]) VALUES (17, N'C2042', 5, CAST(3.00 AS Decimal(3, 2)))
SET IDENTITY_INSERT [dbo].[StudentGrade] OFF
ALTER TABLE [dbo].[Course] WITH CHECK ADD CONSTRAINT [FK_Course_Department] FOREIGN KEY([DepartmentID])
REFERENCES [dbo].[Department] ([DepartmentID])
GO
ALTER TABLE [dbo].[Course] CHECK CONSTRAINT [FK_Course_Department]
GO
ALTER TABLE [dbo].[StudentGrade] WITH CHECK ADD CONSTRAINT [FK_StudentGrade_Student] FOREIGN KEY([StudentID])
REFERENCES [dbo].[Person] ([PersonID])
GO
ALTER TABLE [dbo].[StudentGrade] CHECK CONSTRAINT [FK_StudentGrade_Student]
GO
接下来，编译并执行以下操作：
using System;
using System.Data;
using Microsoft.Data.SqlClient;
using System.Threading.Tasks;
class Program
{
static class SqlHelper
{
// Set the connection, command, and then execute the command with non query.
public static Int32 ExecuteNonQuery(String connectionString, String commandText,
CommandType commandType, params SqlParameter[] parameters)
{
using (SqlConnection conn = new SqlConnection(connectionString))
{
using (SqlCommand cmd = new SqlCommand(commandText, conn))
{
// There're three command types: StoredProcedure, Text, TableDirect. The TableDirect
// type is only for OLE DB.
cmd.CommandType = commandType;
cmd.Parameters.AddRange(parameters);
conn.Open();
return cmd.ExecuteNonQuery();
}
}
}
// Set the connection, command, and then execute the command and only return one value.
public static Object ExecuteScalar(String connectionString, String commandText,
CommandType commandType, params SqlParameter[] parameters)
{
using (SqlConnection conn = new SqlConnection(connectionString))
{
using (SqlCommand cmd = new SqlCommand(commandText, conn))
{
cmd.CommandType = commandType;
cmd.Parameters.AddRange(parameters);
conn.Open();
return cmd.ExecuteScalar();
}
}
}
// Set the connection, command, and then execute the command with query and return the reader.
public static SqlDataReader ExecuteReader(String connectionString, String commandText,
CommandType commandType, params SqlParameter[] parameters)
{
SqlConnection conn = new SqlConnection(connectionString);
using (SqlCommand cmd = new SqlCommand(commandText, conn))
{
cmd.CommandType = commandType;
cmd.Parameters.AddRange(parameters);
conn.Open();
// When using CommandBehavior.CloseConnection, the connection will be closed when the
// IDataReader is closed.
SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
return reader;
}
}
}
static void Main(string[] args)
{
String connectionString = "Data Source=(local);Initial Catalog=MySchool;Integrated Security=True;";
CountCourses(connectionString, 2012);
Console.WriteLine();
Console.WriteLine("Following result is the departments that started from 2007:");
GetDepartments(connectionString, 2007);
Console.WriteLine();
Console.WriteLine("Add the credits when the credits of course is lower than 4.");
AddCredits(connectionString, 4);
Console.WriteLine();
Console.WriteLine("Please press any key to exit...");
Console.ReadKey();
}
static void CountCourses(String connectionString, Int32 year)
{
String commandText = "Select Count([CourseID]) FROM [MySchool].[dbo].[Course] Where Year=@Year";
SqlParameter parameterYear = new SqlParameter("@Year", SqlDbType.Int);
parameterYear.Value = year;
Object oValue = SqlHelper.ExecuteScalar(connectionString, commandText, CommandType.Text, parameterYear);
Int32 count;
if (Int32.TryParse(oValue.ToString(), out count))
Console.WriteLine("There {0} {1} course{2} in {3}.", count > 1 ? "are" : "is", count, count > 1 ? "s" : null, year);
}
// Display the Departments that start from the specified year.
static void GetDepartments(String connectionString, Int32 year)
{
String commandText = "dbo.GetDepartmentsOfSpecifiedYear";
// Specify the year of StartDate
SqlParameter parameterYear = new SqlParameter("@Year", SqlDbType.Int);
parameterYear.Value = year;
// When the direction of parameter is set as Output, you can get the value after
// executing the command.
SqlParameter parameterBudget = new SqlParameter("@BudgetSum", SqlDbType.Money);
parameterBudget.Direction = ParameterDirection.Output;
using (SqlDataReader reader = SqlHelper.ExecuteReader(connectionString, commandText,
CommandType.StoredProcedure, parameterYear, parameterBudget))
{
Console.WriteLine("{0,-20}{1,-20}{2,-20}{3,-20}", "Name", "Budget", "StartDate",
"Administrator");
while (reader.Read())
{
Console.WriteLine("{0,-20}{1,-20:C}{2,-20:d}{3,-20}", reader["Name"],
reader["Budget"], reader["StartDate"], reader["Administrator"]);
}
}
Console.WriteLine("{0,-20}{1,-20:C}", "Sum:", parameterBudget.Value);
}
// If credits of course is lower than the certain value, the method will add the credits.
static void AddCredits(String connectionString, Int32 creditsLow)
{
String commandText = "Update [MySchool].[dbo].[Course] Set Credits=Credits+1 Where Credits<@Credits";
SqlParameter parameterCredits = new SqlParameter("@Credits", creditsLow);
Int32 rows = SqlHelper.ExecuteNonQuery(connectionString, commandText, CommandType.Text, parameterCredits);
Console.WriteLine("{0} row{1} {2} updated.", rows, rows > 1 ? "s" : null, rows > 1 ? "are" : "is");
}
}
注解
创建 实例 SqlCommand 时，读/写属性设置为其初始值。 有关这些值的列表，请参阅 SqlCommand 构造函数。
SqlCommand具有以下用于在SQL Server数据库上执行命令的方法：
| 项 | 说明 |
|---|---|
| BeginExecuteNonQuery | 启动此 SqlCommand描述的 Transact-SQL 语句或存储过程的异步执行，通常执行 INSERT、DELETE、UPDATE 和 SET 语句等命令。 对 的每个调用 BeginExecuteNonQuery 都必须与完成操作的调用配对，该调用 EndExecuteNonQuery 通常在单独的线程上完成操作。 |
| BeginExecuteReader | 启动由此 SqlCommand 描述的 Transact-SQL 语句或存储过程的异步执行，并从服务器检索一个或多个结果集。 对 的每个调用 BeginExecuteReader 都必须与完成操作的调用配对，该调用 EndExecuteReader 通常在单独的线程上完成操作。 |
| BeginExecuteXmlReader | 启动此 SqlCommand 描述的 Transact-SQL 语句或存储过程的异步执行。 对 的每个调用 BeginExecuteXmlReader 都必须与对 EndExecuteXmlReader的调用配对，该调用通常会在单独的线程上完成操作，并返回 一个 XmlReader 对象。 |
| ExecuteReader | 执行返回行的命令。 为了提高性能， ExecuteReader 使用 Transact-SQL sp_executesql 系统存储过程调用命令。 因此， ExecuteReader 如果用于执行 Transact-SQL SET 语句等命令，则可能不会产生所需的效果。 |
| ExecuteNonQuery | 执行 Transact-SQL INSERT、DELETE、UPDATE 和 SET 语句等命令。 |
| ExecuteScalar | 检索单个值 (例如，从数据库) 聚合值。 |
| ExecuteXmlReader | 将 CommandText 发送到 Connection，并生成一个 XmlReader 对象。 |
可以重置 属性 CommandText 并重用 对象 SqlCommand 。 但是，必须先关闭 ， SqlDataReader 然后才能执行新的或上一个命令。
SqlException如果 由执行 的方法生成 ，SqlCommand则 当严重性级别为 19 或更低时， SqlConnection 将保持打开状态。 当严重性级别为 20 或更高时，服务器通常会关闭 SqlConnection。 但是，用户可以重新打开连接并继续操作。
注意
.NET Framework data Provider for SQL Server 不支持无名称参数（也称为序号参数）。
构造函数
| SqlCommand() |
初始化 SqlCommand 类的新实例。 |
| SqlCommand(String) |
使用查询的文本初始化 SqlCommand 类的新实例。 |
| SqlCommand(String, SqlConnection) |
使用查询的文本和 SqlConnection 初始化 类的新实例SqlCommand。 |
| SqlCommand(String, SqlConnection, SqlTransaction) |
使用查询SqlConnection的文本、 和 SqlTransaction 初始化 类的新实例SqlCommand。 |
| SqlCommand(String, SqlConnection, SqlTransaction, SqlCommandColumnEncryptionSetting) |
使用指定的命令文本、连接、事务和加密设置初始化 SqlCommand 类的新实例。 |
属性
| ColumnEncryptionSetting |
获取此命令的列加密设置。 |
| CommandText |
获取或设置要在数据源中执行的 Transact-SQL 语句、表名或存储过程。 |
| CommandTimeout |
获取或设置在终止尝试执行命令并生成错误之前的等待时间（以秒为单位）。 默认为 30 秒。 |
| CommandType |
获取或设置一个值，该值指示解释 CommandText 属性的方式。 |
| Connection |
获取或设置 SqlConnection 的此实例 SqlCommand 使用的 。 |
| DesignTimeVisible |
获取或设置一个值，该值指示命令对象是否应在 Windows 窗体设计器控件中可见。 |
| EnableOptimizedParameterBinding |
获取或设置一个值，该值指示在将命令提交到SQL Server时，命令对象是否应禁用 Output 和 InputOutput 方向来优化参数性能。 |
| Notification |
获取或设置一个指定绑定到此命令的 SqlNotificationRequest 对象的值。 |
| NotificationAutoEnlist |
获取或设置一个值，该值指示应用程序是否应自动接收来自通用 SqlDependency 对象的查询通知。 |
| Parameters | |
| RetryLogicProvider |
获取或设置一个指定绑定到此命令的 SqlRetryLogicBaseProvider 对象的值。 |
| Transaction |
获取或设置要在其中执行 SqlTransaction 的 SqlCommand。 |
| UpdatedRowSource |
获取或设置当 由 的 DbDataAdapterUpdate 方法使用时，命令结果如何应用于 DataRow 。 |
方法
事件
| StatementCompleted |
当 Transact-SQL 语句执行完成时发生。 |
显式接口实现
| ICloneable.Clone() |
表示要对 SQL Server 数据库执行的一个 Transact-SQL 语句或存储过程。 此类不能被继承。 |