Bagikan melalui

SqlCommand.Cancel Metode

  • Referensi

Definisi

Ruang nama:
System.Data.SqlClient
Rakitan:
System.Data.SqlClient.dll
Rakitan:
System.Data.dll
Rakitan:
netstandard.dll, System.Data.SqlClient.dll
Paket:
System.Data.SqlClient v4.8.6

Mencoba membatalkan eksekusi SqlCommand.

public:
 override void Cancel();
public:
 virtual void Cancel();
public override void Cancel ();
public void Cancel ();
override this.Cancel : unit -> unit
abstract member Cancel : unit -> unit
override this.Cancel : unit -> unit
Public Overrides Sub Cancel ()
Public Sub Cancel ()

Penerapan

Cancel()

Contoh

Contoh berikut menunjukkan penggunaan Cancel metode .

using System;
using System.Data;
using System.Data.SqlClient;
using System.Threading;

class Program
{
    private static SqlCommand m_rCommand;

    public static SqlCommand Command
    {
        get { return m_rCommand; }
        set { m_rCommand = value; }
    }

    public static void Thread_Cancel()
    {
        Command.Cancel();
    }

    static void Main()
    {
        string connectionString = GetConnectionString();
        try
        {
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();

                Command = connection.CreateCommand();
                Command.CommandText = "DROP TABLE TestCancel";
                try
                {
                    Command.ExecuteNonQuery();
                }
                catch { }

                Command.CommandText = "CREATE TABLE TestCancel(co1 int, co2 char(10))";
                Command.ExecuteNonQuery();
                Command.CommandText = "INSERT INTO TestCancel VALUES (1, '1')";
                Command.ExecuteNonQuery();

                Command.CommandText = "SELECT * FROM TestCancel";
                SqlDataReader reader = Command.ExecuteReader();

                Thread rThread2 = new Thread(new ThreadStart(Thread_Cancel));
                rThread2.Start();
                rThread2.Join();

                reader.Read();
                System.Console.WriteLine(reader.FieldCount);
                reader.Close();
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
    }
    static private string GetConnectionString()
    {
        // To avoid storing the connection string in your code,
        // you can retrieve it from a configuration file.
        return "Data Source=(local);Initial Catalog=AdventureWorks;"
            + "Integrated Security=SSPI";
    }
}

Imports System.Data
Imports System.Data.SqlClient
Imports System.Threading

Module Module1
    Private m_rCommand As SqlCommand

    Public Property Command() As SqlCommand
        Get
            Return m_rCommand
        End Get
        Set(ByVal value As SqlCommand)
            m_rCommand = value
        End Set
    End Property

    Public Sub Thread_Cancel()
        Command.Cancel()
    End Sub

    Sub Main()
        Dim connectionString As String = GetConnectionString()

        Try
            Using connection As New SqlConnection(connectionString)

                connection.Open()

                Command = connection.CreateCommand()
                Command.CommandText = "DROP TABLE TestCancel"
                Try
                    Command.ExecuteNonQuery()
                Catch
                End Try

                Command.CommandText = "CREATE TABLE TestCancel(co1 int, co2 char(10))"
                Command.ExecuteNonQuery()
                Command.CommandText = "INSERT INTO TestCancel VALUES (1, '1')"
                Command.ExecuteNonQuery()

                Command.CommandText = "SELECT * FROM TestCancel"
                Dim reader As SqlDataReader = Command.ExecuteReader()

                Dim rThread2 As New Thread( _
                    New ThreadStart(AddressOf Thread_Cancel))

                rThread2.Start()
                rThread2.Join()

                reader.Read()
                Console.WriteLine(reader.FieldCount)
                reader.Close()
            End Using

        Catch ex As Exception
            Console.WriteLine(ex.Message)
        End Try
    End Sub

    Private Function GetConnectionString() As String
        ' To avoid storing the connection string in your code,  
        ' you can retrieve it from a configuration file.
        Return "Data Source=(local);Initial Catalog=AdventureWorks;" _
           & "Integrated Security=SSPI;"
    End Function
End Module

Keterangan

Jika tidak ada yang dibatalkan, tidak ada yang terjadi. Namun, jika ada perintah dalam proses, dan upaya untuk membatalkan gagal, tidak ada pengecualian yang dihasilkan.

Dalam beberapa kasus yang jarang terjadi, jika Anda memanggil ExecuteReader, maka panggil Close (secara implisit atau eksplisit) sebelum memanggil Cancel, dan kemudian memanggil Cancel, perintah batalkan tidak akan dikirim ke SQL Server dan tataan hasil dapat terus mengalir setelah Anda memanggil Close. Untuk menghindari hal ini, pastikan Anda memanggil Cancel sebelum menutup pembaca atau koneksi.

Berlaku untuk

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