SqlCommand Klas

Definitie

public ref class SqlCommand sealed : System::ComponentModel::Component, ICloneable, IDisposable, System::Data::IDbCommand

public ref class SqlCommand sealed : System::Data::Common::DbCommand, ICloneable

public sealed class SqlCommand : System.ComponentModel.Component, ICloneable, IDisposable, System.Data.IDbCommand

public sealed class SqlCommand : System.Data.Common.DbCommand, ICloneable

type SqlCommand = class
    inherit Component
    interface IDbCommand
    interface IDisposable
    interface ICloneable

type SqlCommand = class
    inherit DbCommand
    interface ICloneable

Public NotInheritable Class SqlCommand
Inherits Component
Implements ICloneable, IDbCommand, IDisposable

Public NotInheritable Class SqlCommand
Inherits DbCommand
Implements ICloneable

Overname

Object

MarshalByRefObject

Component

SqlCommand

Overname

Object

MarshalByRefObject

Component

DbCommand

SqlCommand

Implementeringen

IDbCommand ICloneable IDisposable

Voorbeelden

In het volgende voorbeeld wordt een SqlConnection, a SqlCommanden een SqlDataReader. Het voorbeeld leest de gegevens door en schrijft deze naar de console. Ten slotte wordt in het voorbeeld de SqlDataReader en vervolgens de SqlConnection codeblokken gesloten terwijl deze wordt Using afgesloten.

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]));
            }
        }
    }
}

Public Sub ReadOrderData(ByVal connectionString As String)
    Dim queryString As String = _
        "SELECT OrderID, CustomerID FROM dbo.Orders;"
    Using connection As New SqlConnection(connectionString)
        Dim command As New SqlCommand(queryString, connection)
        connection.Open()
        Dim reader As SqlDataReader = command.ExecuteReader()
        Try
            While reader.Read()
                Console.WriteLine(String.Format("{0}, {1}", _
                    reader(0), reader(1)))
            End While
        Finally
            ' Always call Close when done reading.
            reader.Close()
        End Try
    End Using
End Sub

In het volgende voorbeeld ziet u hoe u verschillende typen SqlCommand-objecten maakt en uitvoert.

Eerst moet u de voorbeelddatabase maken door het volgende script uit te voeren:

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

Compileer en voer vervolgens het volgende uit:

using System;
using System.Data;
using System.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;Asynchronous Processing=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");
   }
}

Opmerkingen

Wanneer er een exemplaar van SqlCommand wordt gemaakt, worden de eigenschappen voor lezen/schrijven ingesteld op de oorspronkelijke waarden. Zie de SqlCommand constructor voor een lijst met deze waarden.

SqlCommand bevat de volgende methoden voor het uitvoeren van opdrachten in een SQL Server-database:

U kunt de CommandText eigenschap opnieuw instellen en het SqlCommand object opnieuw gebruiken. U moet echter de SqlDataReader opdracht sluiten voordat u een nieuwe of vorige opdracht kunt uitvoeren.

Als een wordt SqlException gegenereerd door de methode waarmee een SqlCommandwordt uitgevoerd, blijft het SqlConnection open wanneer het ernstniveau 19 of minder is. Wanneer het ernstniveau 20 of hoger is, wordt de server gewoonlijk gesloten SqlConnection. De gebruiker kan de verbinding echter opnieuw openen en doorgaan.

Zie ook

• Gegevens ophalen en wijzigen in ADO.NET
• SQL Server en ADO.NET
• overzicht van ADO.NET