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。
表示针对SQL Server数据库执行的Transact-SQL语句或存储过程。 无法继承此类。
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
以下示例创建一个 SqlConnection、一个 SqlCommand和一个 SqlDataReader。 该示例读取数据，并将其写入控制台。 最后，该示例关闭代码块，然后在SqlDataReader退出代码块时SqlConnection关闭Using该示例。
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，编译并执行以下内容：
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/写属性将设置为其初始值。 有关这些值的列表，请参阅 SqlCommand 构造函数。
SqlCommand 在 SQL Server 数据库中执行命令的功能如下：
| Item | Description |
|---|---|
| BeginExecuteNonQuery | 启动由此 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。 每次调用都必须与完成操作的调用BeginExecuteNonQueryEndExecuteNonQuery配对，通常是在单独的线程上。 |
| BeginExecuteReader | 启动由此描述 SqlCommand 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。 每次调用都必须与完成操作的调用BeginExecuteReaderEndExecuteReader配对，通常是在单独的线程上。 |
| BeginExecuteXmlReader | 启动由此描述 SqlCommand的 Transact-SQL 语句或存储过程的异步执行。 每次调用都必须与调用配对，该调用BeginExecuteXmlReaderEndExecuteXmlReader完成操作，通常在单独的线程上，并返回一个XmlReader对象。 |
| ExecuteReader | 执行返回行的命令。 为了提高性能， ExecuteReader 请使用 Transact-SQL sp_executesql 系统存储过程调用命令。 因此， ExecuteReader 如果用于执行命令（如 Transact-SQL SET 语句），则可能没有所需的效果。 |
| ExecuteNonQuery | 执行 Transact-SQL INSERT、DELETE、UPDATE 和 SET 语句等命令。 |
| ExecuteScalar | 从数据库检索单个值（例如聚合值）。 |
| ExecuteXmlReader | 将对象 CommandText 发送到 Connection 并生成对象 XmlReader 。 |
可以重置 CommandText 属性并重复使用 SqlCommand 该对象。 但是，必须先关闭该命令 SqlDataReader ，然后才能执行新的或以前的命令。
如果由执行 a 的方法生成 a SqlExceptionSqlCommand， SqlConnection 则当严重性级别为 19 或更少时，将保持打开状态。 当严重级别为 20 或更大时，服务器通常会关闭 。SqlConnection 但是，用户可以重新打开连接并继续。
Note
.NET Framework Data Provider for SQL Server 不支持无名称（也称为序号）参数。
构造函数
| 名称 | 说明 |
|---|---|
| SqlCommand() |
初始化 SqlCommand 类的新实例。 |
| 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类的新实例 SqlCommand 。 |
| SqlCommand(String, SqlConnection, SqlTransaction) |
使用查询文本、查询文本和 < |
| SqlCommand(String, SqlConnection) |
使用查询的文本和一个 SqlCommandSqlConnection. |
| SqlCommand(String) |
使用查询的文本初始化类的新实例 SqlCommand 。 |
属性
| 名称 | 说明 |
|---|---|
| ColumnEncryptionSetting |
获取此命令的列加密设置。 |
| CommandText |
获取或设置在数据源中执行的 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（以秒为单位）的等待时间。 默认值为 30 秒。 |
| CommandType |
获取或设置一个值，该值指示如何 CommandText 解释属性。 |
| Connection |
获取或设置 SqlConnection 此实例 SqlCommand所使用的 。 |
| 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，该值指示命令对象在将命令提交到SQL Server时是否应禁用 Output 和 InputOutput 方向来优化参数性能。 |
| Notification |
获取或设置一个值，该值指定 SqlNotificationRequest 绑定到此命令的对象。 |
| NotificationAutoEnlist |
获取或设置一个值，该值指示应用程序是否应从公共 SqlDependency 对象自动接收查询通知。 |
| Parameters | |
| RetryLogicProvider |
获取或设置一个值，该值指定 SqlRetryLogicBaseProvider 绑定到此命令的对象。 |
| Transaction |
获取或设置 SqlTransaction 执行范围 SqlCommand 。 |
| UpdatedRowSource |
获取或设置命令结果DataRow应用于方法 |
方法
活动
| 名称 | 说明 |
|---|---|
| StatementCompleted |
执行 Transact-SQL 语句完成时发生。 |
显式接口实现
| 名称 | 说明 |
|---|---|
| ICloneable.Clone() |
表示针对SQL Server数据库执行的Transact-SQL语句或存储过程。 无法继承此类。 |