SqlCommand.BeginExecuteNonQuery Método

Definición

Inicia la ejecución asincrónica de la instrucción de Transact-SQL o del procedimiento almacenado que describe SqlCommand.Initiates the asynchronous execution of the Transact-SQL statement or stored procedure that is described by this SqlCommand.

Sobrecargas

BeginExecuteNonQuery()

Inicia la ejecución asincrónica de la instrucción de Transact-SQL o del procedimiento almacenado que describe SqlCommand.Initiates the asynchronous execution of the Transact-SQL statement or stored procedure that is described by this SqlCommand.

BeginExecuteNonQuery(AsyncCallback, Object)

Inicia la ejecución asincrónica de la instrucción de Transact-SQL o del procedimiento almacenado que describe SqlCommand, dados un procedimiento de devolución de llamada e información de estado.Initiates the asynchronous execution of the Transact-SQL statement or stored procedure that is described by this SqlCommand, given a callback procedure and state information.

BeginExecuteNonQuery()

Inicia la ejecución asincrónica de la instrucción de Transact-SQL o del procedimiento almacenado que describe SqlCommand.Initiates the asynchronous execution of the Transact-SQL statement or stored procedure that is described by this SqlCommand.

public:
 IAsyncResult ^ BeginExecuteNonQuery();
public IAsyncResult BeginExecuteNonQuery ();
member this.BeginExecuteNonQuery : unit -> IAsyncResult
Public Function BeginExecuteNonQuery () As IAsyncResult

Devoluciones

IAsyncResult que se puede utilizar para sondear y/o esperar los resultados; este valor también es necesario al invocar a EndExecuteNonQuery(IAsyncResult), que devuelve el número de filas afectado.An IAsyncResult that can be used to poll or wait for results, or both; this value is also needed when invoking EndExecuteNonQuery(IAsyncResult), which returns the number of affected rows.

Excepciones

Se usó un elemento SqlDbType distinto de Binary o VarBinary cuando Value se estableció en Stream.A SqlDbType other than Binary or VarBinary was used when Value was set to Stream. Para más información sobre el streaming, vea Compatibilidad con el streaming de SqlClient.For more information about streaming, see SqlClient Streaming Support.

O bien,-or-

Se usó un elemento SqlDbType distinto de Char, NChar, NVarChar, VarCharo Xml cuando Value se estableció en TextReader.A SqlDbType other than Char, NChar, NVarChar, VarChar, or Xml was used when Value was set to TextReader.

O bien,-or-

Se usó un elemento SqlDbType distinto de Xml cuando Value se estableció en XmlReader.A SqlDbType other than Xml was used when Value was set to XmlReader.

Cualquier error que se produjo al ejecutar el texto del comando.Any error that occurred while executing the command text.

O bien,-or-

Se agotó el tiempo de espera durante una operación de streaming.A timeout occurred during a streaming operation. Para más información sobre el streaming, vea Compatibilidad con el streaming de SqlClient.For more information about streaming, see SqlClient Streaming Support.

El par nombre/valor "Asynchronous Processing=true" no se incluyó dentro de la cadena de conexión que define la conexión para este SqlCommand.The name/value pair "Asynchronous Processing=true" was not included within the connection string defining the connection for this SqlCommand.

O bien,-or-

La SqlConnection se cerró o se interrumpió durante una operación de streaming.The SqlConnection closed or dropped during a streaming operation. Para más información sobre el streaming, vea Compatibilidad con el streaming de SqlClient.For more information about streaming, see SqlClient Streaming Support.

Se produjo un error en un objeto Stream, XmlReader o TextReader durante una operación de streaming.An error occurred in a Stream, XmlReader or TextReader object during a streaming operation. Para más información sobre el streaming, vea Compatibilidad con el streaming de SqlClient.For more information about streaming, see SqlClient Streaming Support.

El objeto Stream, XmlReader o TextReader se cerró durante una operación de transmisión por secuencias.The Stream, XmlReader or TextReader object was closed during a streaming operation. Para más información sobre el streaming, vea Compatibilidad con el streaming de SqlClient.For more information about streaming, see SqlClient Streaming Support.

Ejemplos

La siguiente aplicación de consola crea datos de actualización en la base de datos de ejemplo AdventureWorks , haciendo su trabajo de forma asincrónica.The following console application creates updates data within the AdventureWorks sample database, doing its work asynchronously. Para emular un proceso cuya ejecución tiene una larga duración, en este ejemplo se inserta una instrucción WAITFOR en el texto de comando.In order to emulate a long-running process, this example inserts a WAITFOR statement in the command text. Normalmente, no se realizaría ningún trabajo para que los comandos se ejecuten más lentamente, pero en este caso resulta más fácil mostrar el comportamiento asincrónico.Normally, you would not take efforts to make your commands run slower, but doing this in this case makes it easier to demonstrate the asynchronous behavior.

using System.Data.SqlClient;

class Class1
{
    static void Main()
    {
        // This is a simple example that demonstrates the usage of the 
        // BeginExecuteNonQuery functionality.
        // The WAITFOR statement simply adds enough time to prove the 
        // asynchronous nature of the command.
      
        string commandText = 
            "UPDATE Production.Product SET ReorderPoint = ReorderPoint + 1 " + 
            "WHERE ReorderPoint Is Not Null;" + 
            "WAITFOR DELAY '0:0:3';" + 
            "UPDATE Production.Product SET ReorderPoint = ReorderPoint - 1 " + 
            "WHERE ReorderPoint Is Not Null";

        RunCommandAsynchronously(commandText, GetConnectionString());

        Console.WriteLine("Press ENTER to continue.");
        Console.ReadLine();
    }

    private static void RunCommandAsynchronously(
        string commandText, string connectionString)
    {
        // Given command text and connection string, asynchronously execute
        // the specified command against the connection. For this example,
        // the code displays an indicator as it is working, verifying the 
        // asynchronous behavior. 
        using (SqlConnection connection = 
                   new SqlConnection(connectionString))
        {
            try
            {
                int count = 0;
                SqlCommand command = new SqlCommand(commandText, connection);
                connection.Open();

                IAsyncResult result = command.BeginExecuteNonQuery();
                while (!result.IsCompleted)
                {
                    Console.WriteLine("Waiting ({0})", count++);
                    // Wait for 1/10 second, so the counter
                    // does not consume all available resources 
                    // on the main thread.
                    System.Threading.Thread.Sleep(100);
                }
                Console.WriteLine("Command complete. Affected {0} rows.", 
                    command.EndExecuteNonQuery(result));
            }
            catch (SqlException ex)
            {
                Console.WriteLine("Error ({0}): {1}", ex.Number, ex.Message);
            }
            catch (InvalidOperationException ex)
            {
                Console.WriteLine("Error: {0}", ex.Message);
            }
            catch (Exception ex)
            {
                // You might want to pass these errors
                // back out to the caller.
                Console.WriteLine("Error: {0}", ex.Message);
            }
        }
    }

    private static string GetConnectionString()
    {
        // To avoid storing the connection string in your code,            
        // you can retrieve it from a configuration file. 

        // If you have not included "Asynchronous Processing=true" in the
        // connection string, the command is not able
        // to execute asynchronously.
        return "Data Source=(local);Integrated Security=SSPI;" +
            "Initial Catalog=AdventureWorks; Asynchronous Processing=true";
    } 
}
Imports System.Data.SqlClient

Module Module1

    Sub Main()
        ' This is a simple example that demonstrates the usage of the 
        ' BeginExecuteNonQuery functionality.
        ' The WAITFOR statement simply adds enough time to prove the 
        ' asynchronous nature of the command.
        Dim commandText As String = _
         "UPDATE Production.Product SET ReorderPoint = ReorderPoint + 1 " & _
         "WHERE ReorderPoint Is Not Null;" & _
         "WAITFOR DELAY '0:0:3';" & _
         "UPDATE Production.Product SET ReorderPoint = ReorderPoint - 1 " & _
         "WHERE ReorderPoint Is Not Null"

        RunCommandAsynchronously(commandText, GetConnectionString())

        Console.WriteLine("Press ENTER to continue.")
        Console.ReadLine()
    End Sub

    Private Sub RunCommandAsynchronously( _
     ByVal commandText As String, ByVal connectionString As String)

        ' Given command text and connection string, asynchronously execute
        ' the specified command against the connection. For this example,
        ' the code displays an indicator as it is working, verifying the 
        ' asynchronous behavior. 
        Using connection As New SqlConnection(connectionString)
            Try
                Dim count As Integer = 0
                Dim command As New SqlCommand(commandText, connection)
                connection.Open()
                Dim result As IAsyncResult = command.BeginExecuteNonQuery()
                While Not result.IsCompleted
                    Console.WriteLine("Waiting ({0})", count)
                    ' Wait for 1/10 second, so the counter
                    ' does not consume all available resources 
                    ' on the main thread.
                    Threading.Thread.Sleep(100)
                    count += 1
                End While
                Console.WriteLine("Command complete. Affected {0} rows.", _
                    command.EndExecuteNonQuery(result))
            Catch ex As SqlException
                Console.WriteLine("Error ({0}): {1}", ex.Number, ex.Message)
            Catch ex As InvalidOperationException
                Console.WriteLine("Error: {0}", ex.Message)
            Catch ex As Exception
                ' You might want to pass these errors
                ' back out to the caller.
                Console.WriteLine("Error: {0}", ex.Message)
            End Try
        End Using
    End Sub

    Private Function GetConnectionString() As String
        ' To avoid storing the connection string in your code,            
        ' you can retrieve it from a configuration file. 

        ' If you have not included "Asynchronous Processing=true" in the
        ' connection string, the command is not able
        ' to execute asynchronously.
        Return "Data Source=(local);Integrated Security=SSPI;" & _
          "Initial Catalog=AdventureWorks; Asynchronous Processing=true"
    End Function
End Module

Comentarios

El método BeginExecuteNonQuery inicia el proceso de ejecución asincrónica de una instrucción de Transact-SQLTransact-SQL o un procedimiento almacenado que no devuelve filas, de modo que se puedan ejecutar otras tareas simultáneamente mientras se ejecuta la instrucción.The BeginExecuteNonQuery method starts the process of asynchronously executing a Transact-SQLTransact-SQL statement or stored procedure that does not return rows, so that other tasks can run concurrently while the statement is executing. Cuando la instrucción se haya completado, los desarrolladores deben llamar al método EndExecuteNonQuery para finalizar la operación.When the statement has completed, developers must call the EndExecuteNonQuery method to finish the operation. El método BeginExecuteNonQuery vuelve inmediatamente, pero hasta que el código ejecuta la llamada al método EndExecuteNonQuery correspondiente, no debe ejecutar ninguna otra llamada que inicie una ejecución sincrónica o asincrónica en el mismo objeto SqlCommand.The BeginExecuteNonQuery method returns immediately, but until the code executes the corresponding EndExecuteNonQuery method call, it must not execute any other calls that start a synchronous or asynchronous execution against the same SqlCommand object. La llamada a la EndExecuteNonQuery antes de que se complete la ejecución del comando hace que el objeto SqlCommand se bloquee hasta que finalice la ejecución.Calling the EndExecuteNonQuery before the command's execution is completed causes the SqlCommand object to block until the execution is finished.

Tenga en cuenta que el texto y los parámetros del comando se envían al servidor de forma sincrónica.Note that the command text and parameters are sent to the server synchronously. Si se envían comandos grandes o muchos parámetros, este método puede bloquearse durante las operaciones de escritura.If a large command or many parameters are sent, this method may block during writes. Después de enviar el comando, el método vuelve inmediatamente sin esperar una respuesta del servidor; es decir, las lecturas son asincrónicas.After the command is sent, the method returns immediately without waiting for an answer from the server--that is, reads are asynchronous.

Dado que esta sobrecarga no admite un procedimiento de devolución de llamada, los desarrolladores deben sondear para determinar si el comando se ha completado, utilizando la propiedad IsCompleted del IAsyncResult devuelto por el método BeginExecuteNonQuery; o bien, espere a que se completen uno o varios comandos mediante la propiedad AsyncWaitHandle del IAsyncResultdevuelto.Because this overload does not support a callback procedure, developers must either poll to determine whether the command has completed, using the IsCompleted property of the IAsyncResult returned by the BeginExecuteNonQuery method; or wait for the completion of one or more commands using the AsyncWaitHandle property of the returned IAsyncResult.

Este método omite la propiedad CommandTimeout.This method ignores the CommandTimeout property.

Consulte también:

BeginExecuteNonQuery(AsyncCallback, Object)

Inicia la ejecución asincrónica de la instrucción de Transact-SQL o del procedimiento almacenado que describe SqlCommand, dados un procedimiento de devolución de llamada e información de estado.Initiates the asynchronous execution of the Transact-SQL statement or stored procedure that is described by this SqlCommand, given a callback procedure and state information.

public:
 IAsyncResult ^ BeginExecuteNonQuery(AsyncCallback ^ callback, System::Object ^ stateObject);
public IAsyncResult BeginExecuteNonQuery (AsyncCallback callback, object stateObject);
member this.BeginExecuteNonQuery : AsyncCallback * obj -> IAsyncResult
Public Function BeginExecuteNonQuery (callback As AsyncCallback, stateObject As Object) As IAsyncResult

Parámetros

callback
AsyncCallback

Delegado AsyncCallback que se invoca cuando finaliza la ejecución del comando.An AsyncCallback delegate that is invoked when the command's execution has completed. Pase null (Nothing en Microsoft Visual Basic) para indicar que no se requiere ninguna devolución de llamada.Pass null (Nothing in Microsoft Visual Basic) to indicate that no callback is required.

stateObject
Object

Objeto de estado definido por el usuario que se pasa al procedimiento de devolución de llamada.A user-defined state object that is passed to the callback procedure. Recupere este objeto desde el procedimiento de devolución de llamada mediante la propiedad AsyncState.Retrieve this object from within the callback procedure using the AsyncState property.

Devoluciones

IAsyncResult que se puede utilizar para sondear y/o esperar los resultados; este valor también es necesario al invocar a EndExecuteNonQuery(IAsyncResult), que devuelve el número de filas afectado.An IAsyncResult that can be used to poll or wait for results, or both; this value is also needed when invoking EndExecuteNonQuery(IAsyncResult), which returns the number of affected rows.

Excepciones

Se usó un elemento SqlDbType distinto de Binary o VarBinary cuando Value se estableció en Stream.A SqlDbType other than Binary or VarBinary was used when Value was set to Stream. Para más información sobre el streaming, vea Compatibilidad con el streaming de SqlClient.For more information about streaming, see SqlClient Streaming Support.

O bien,-or-

Se usó un elemento SqlDbType distinto de Char, NChar, NVarChar, VarCharo Xml cuando Value se estableció en TextReader.A SqlDbType other than Char, NChar, NVarChar, VarChar, or Xml was used when Value was set to TextReader.

O bien,-or-

Se usó un elemento SqlDbType distinto de Xml cuando Value se estableció en XmlReader.A SqlDbType other than Xml was used when Value was set to XmlReader.

Cualquier error que se produjo al ejecutar el texto del comando.Any error that occurred while executing the command text.

O bien,-or-

Se agotó el tiempo de espera durante una operación de streaming.A timeout occurred during a streaming operation. Para más información sobre el streaming, vea Compatibilidad con el streaming de SqlClient.For more information about streaming, see SqlClient Streaming Support.

El par nombre/valor "Asynchronous Processing=true" no se incluyó dentro de la cadena de conexión que define la conexión para este SqlCommand.The name/value pair "Asynchronous Processing=true" was not included within the connection string defining the connection for this SqlCommand.

O bien,-or-

La SqlConnection se cerró o se interrumpió durante una operación de streaming.The SqlConnection closed or dropped during a streaming operation. Para más información sobre el streaming, vea Compatibilidad con el streaming de SqlClient.For more information about streaming, see SqlClient Streaming Support.

Se produjo un error en un objeto Stream, XmlReader o TextReader durante una operación de streaming.An error occurred in a Stream, XmlReader or TextReader object during a streaming operation. Para más información sobre el streaming, vea Compatibilidad con el streaming de SqlClient.For more information about streaming, see SqlClient Streaming Support.

El objeto Stream, XmlReader o TextReader se cerró durante una operación de transmisión por secuencias.The Stream, XmlReader or TextReader object was closed during a streaming operation. Para más información sobre el streaming, vea Compatibilidad con el streaming de SqlClient.For more information about streaming, see SqlClient Streaming Support.

Ejemplos

La siguiente aplicación de Windows muestra el uso del método BeginExecuteNonQuery, ejecutando una instrucción Transact-SQL que incluye un retraso de varios segundos (emulando un comando de ejecución prolongada).The following Windows application demonstrates the use of the BeginExecuteNonQuery method, executing a Transact-SQL statement that includes a delay of several seconds (emulating a long-running command).

En este ejemplo se muestran muchas técnicas importantes.This example demonstrates many important techniques. Esto incluye llamar a un método que interactúa con el formulario desde un subproceso independiente.This includes calling a method that interacts with the form from a separate thread. Además, en este ejemplo se muestra cómo debe impedir que los usuarios ejecuten un comando varias veces simultáneamente y cómo debe asegurarse de que el formulario no se cierra antes de que se llame al procedimiento de devolución de llamada.In addition, this example demonstrates how you must block users from executing a command multiple times concurrently, and how you must make sure that the form does not close before the callback procedure is called.

Para realizar este ejemplo, cree una nueva aplicación Windows.To set up this example, create a new Windows application. Coloque un control Button y un control Label en el formulario (aceptando el nombre predeterminado de cada control).Put a Button control and a Label control on the form (accepting the default name for each control). Agregue el código siguiente a la clase del formulario y modifique la cadena de conexión según sea necesario para su entorno.Add the following code to the form's class, modifying the connection string as needed for your environment.

using System.Data.SqlClient;

namespace Microsoft.AdoDotNet.CodeSamples
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        // Hook up the form's Load event handler (you can double-click on 
        // the form's design surface in Visual Studio), and then add 
        // this code to the form's class:
        private void Form1_Load(object sender, EventArgs e)
        {
            this.button1.Click += new System.EventHandler(this.button1_Click);
            this.FormClosing += new System.Windows.Forms.
                FormClosingEventHandler(this.Form1_FormClosing);
        }

        // You need this delegate in order to display text from a thread
        // other than the form's thread. See the HandleCallback
        // procedure for more information.
        // This same delegate matches both the DisplayStatus 
        // and DisplayResults methods.
        private delegate void DisplayInfoDelegate(string Text);

        // This flag ensures that the user does not attempt
        // to restart the command or close the form while the 
        // asynchronous command is executing.
        private bool isExecuting;

        // This example maintains the connection object 
        // externally, so that it is available for closing.
        private SqlConnection connection;

        private static string GetConnectionString()
        {
            // To avoid storing the connection string in your code,            
            // you can retrieve it from a configuration file. 

            // If you have not included "Asynchronous Processing=true" in the
            // connection string, the command is not able
            // to execute asynchronously.
            return "Data Source=(local);Integrated Security=true;" +
                "Initial Catalog=AdventureWorks; Asynchronous Processing=true";
        }

        private void DisplayStatus(string Text)
        {
            this.label1.Text = Text;
        }

        private void DisplayResults(string Text)
        {
            this.label1.Text = Text;
            DisplayStatus("Ready");
        }

        private void Form1_FormClosing(object sender,
            System.Windows.Forms.FormClosingEventArgs e)
        {
            if (isExecuting)
            {
                MessageBox.Show(this, "Cannot close the form until " +
                    "the pending asynchronous command has completed. Please wait...");
                e.Cancel = true;
            }
        }

        private void button1_Click(object sender, System.EventArgs e)
        {
            if (isExecuting)
            {
                MessageBox.Show(this,
                    "Already executing. Please wait until the current query " +
                    "has completed.");
            }
            else
            {
                SqlCommand command = null;
                try
                {
                    DisplayResults("");
                    DisplayStatus("Connecting...");
                    connection = new SqlConnection(GetConnectionString());
                    // To emulate a long-running query, wait for 
                    // a few seconds before working with the data.
                    // This command does not do much, but that's the point--
                    // it does not change your data, in the long run.
                    string commandText =
                        "WAITFOR DELAY '0:0:05';" +
                        "UPDATE Production.Product SET ReorderPoint = ReorderPoint + 1 " +
                        "WHERE ReorderPoint Is Not Null;" +
                        "UPDATE Production.Product SET ReorderPoint = ReorderPoint - 1 " +
                        "WHERE ReorderPoint Is Not Null";

                    command = new SqlCommand(commandText, connection);
                    connection.Open();

                    DisplayStatus("Executing...");
                    isExecuting = true;
                    // Although it is not required that you pass the 
                    // SqlCommand object as the second parameter in the 
                    // BeginExecuteNonQuery call, doing so makes it easier
                    // to call EndExecuteNonQuery in the callback procedure.
                    AsyncCallback callback = new AsyncCallback(HandleCallback);
                    command.BeginExecuteNonQuery(callback, command);
                }
                catch (Exception ex)
                {
                    isExecuting = false;
                    DisplayStatus(string.Format("Ready (last error: {0})", ex.Message));
                    if (connection != null)
                    {
                        connection.Close();
                    }
                }
            }
        }

        private void HandleCallback(IAsyncResult result)
        {
            try
            {
                // Retrieve the original command object, passed
                // to this procedure in the AsyncState property
                // of the IAsyncResult parameter.
                SqlCommand command = (SqlCommand)result.AsyncState;
                int rowCount = command.EndExecuteNonQuery(result);
                string rowText = " rows affected.";
                if (rowCount == 1)
                {
                    rowText = " row affected.";
                }
                rowText = rowCount + rowText;

                // You may not interact with the form and its contents
                // from a different thread, and this callback procedure
                // is all but guaranteed to be running from a different thread
                // than the form. Therefore you cannot simply call code that 
                // displays the results, like this:
                // DisplayResults(rowText)

                // Instead, you must call the procedure from the form's thread.
                // One simple way to accomplish this is to call the Invoke
                // method of the form, which calls the delegate you supply
                // from the form's thread. 
                DisplayInfoDelegate del = new DisplayInfoDelegate(DisplayResults);
                this.Invoke(del, rowText);
            }
            catch (Exception ex)
            {
                // Because you are now running code in a separate thread, 
                // if you do not handle the exception here, none of your other
                // code catches the exception. Because none of 
                // your code is on the call stack in this thread, there is nothing
                // higher up the stack to catch the exception if you do not 
                // handle it here. You can either log the exception or 
                // invoke a delegate (as in the non-error case in this 
                // example) to display the error on the form. In no case
                // can you simply display the error without executing a delegate
                // as in the try block here. 

                // You can create the delegate instance as you 
                // invoke it, like this:
                this.Invoke(new DisplayInfoDelegate(DisplayStatus),
                    String.Format("Ready(last error: {0}", ex.Message));
            }
            finally
            {
                isExecuting = false;
                if (connection != null)
                {
                    connection.Close();
                }
            }
        }
    }
}
Imports System.Data.SqlClient

Public Class Form1
    ' Add this code to the form's class:
    ' You need this delegate in order to display text from a thread
    ' other than the form's thread. See the HandleCallback
    ' procedure for more information.
    ' This same delegate matches both the DisplayStatus 
    ' and DisplayResults methods.
    Private Delegate Sub DisplayInfoDelegate(ByVal Text As String)

    ' This flag ensures that the user does not attempt
    ' to restart the command or close the form while the 
    ' asynchronous command is executing.
    Private isExecuting As Boolean

    ' This example maintains the connection object 
    ' externally, so that it is available for closing.
    Private connection As SqlConnection

    Private Function GetConnectionString() As String
        ' To avoid storing the connection string in your code,            
        ' you can retrieve it from a configuration file. 

        ' If you have not included "Asynchronous Processing=true" in the
        ' connection string, the command is not able
        ' to execute asynchronously.
        Return "Data Source=(local);Integrated Security=true;" & _
          "Initial Catalog=AdventureWorks; Asynchronous Processing=true"
    End Function

    Private Sub DisplayStatus(ByVal Text As String)
        Me.Label1.Text = Text
    End Sub

    Private Sub DisplayResults(ByVal Text As String)
        Me.Label1.Text = Text
        DisplayStatus("Ready")
    End Sub

    Private Sub Form1_FormClosing(ByVal sender As Object, _
        ByVal e As System.Windows.Forms.FormClosingEventArgs) _
        Handles Me.FormClosing
        If isExecuting Then
            MessageBox.Show(Me, "Cannot close the form until " & _
                "the pending asynchronous command has completed. Please wait...")
            e.Cancel = True
        End If
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles Button1.Click
        If isExecuting Then
            MessageBox.Show(Me, _
               "Already executing. Please wait until the current query " & _
                "has completed.")
        Else
            Dim command As SqlCommand
            Try
                DisplayResults("")
                DisplayStatus("Connecting...")
                connection = New SqlConnection(GetConnectionString())
                ' To emulate a long-running query, wait for 
                ' a few seconds before working with the data.
                ' This command does not do much, but that's the point--
                ' it does not change your data, in the long run.
                Dim commandText As String = _
                    "WAITFOR DELAY '0:0:05';" & _
                    "UPDATE Production.Product SET ReorderPoint = ReorderPoint + 1 " & _
                    "WHERE ReorderPoint Is Not Null;" & _
                    "UPDATE Production.Product SET ReorderPoint = ReorderPoint - 1 " & _
                    "WHERE ReorderPoint Is Not Null"

                command = New SqlCommand(commandText, connection)
                connection.Open()

                DisplayStatus("Executing...")
                isExecuting = True
                ' Although it is not required that you pass the 
                ' SqlCommand object as the second parameter in the 
                ' BeginExecuteNonQuery call, doing so makes it easier
                ' to call EndExecuteNonQuery in the callback procedure.
                Dim callback As New AsyncCallback(AddressOf HandleCallback)
                command.BeginExecuteNonQuery(callback, command)

            Catch ex As Exception
                isExecuting = False
                DisplayStatus(String.Format("Ready (last error: {0})", ex.Message))
                If connection IsNot Nothing Then
                    connection.Close()
                End If
            End Try
        End If
    End Sub

    Private Sub HandleCallback(ByVal result As IAsyncResult)
        Try
            ' Retrieve the original command object, passed
            ' to this procedure in the AsyncState property
            ' of the IAsyncResult parameter.
            Dim command As SqlCommand = CType(result.AsyncState, SqlCommand)
            Dim rowCount As Integer = command.EndExecuteNonQuery(result)
            Dim rowText As String = " rows affected."
            If rowCount = 1 Then
                rowText = " row affected."
            End If
            rowText = rowCount & rowText

            ' You may not interact with the form and its contents
            ' from a different thread, and this callback procedure
            ' is all but guaranteed to be running from a different thread
            ' than the form. Therefore you cannot simply call code that 
            ' displays the results, like this:
            ' DisplayResults(rowText)

            ' Instead, you must call the procedure from the form's thread.
            ' One simple way to accomplish this is to call the Invoke
            ' method of the form, which calls the delegate you supply
            ' from the form's thread. 
            Dim del As New DisplayInfoDelegate(AddressOf DisplayResults)
            Me.Invoke(del, rowText)

        Catch ex As Exception
            ' Because you are now running code in a separate thread, 
            ' if you do not handle the exception here, none of your other
            ' code catches the exception. Because none of your code
            ' is on the call stack in this thread, there is nothing
            ' higher up the stack to catch the exception if you do not 
            ' handle it here. You can either log the exception or 
            ' invoke a delegate (as in the non-error case in this 
            ' example) to display the error on the form. In no case
            ' can you simply display the error without executing a delegate
            ' as in the Try block here. 

            ' You can create the delegate instance as you 
            ' invoke it, like this:
            Me.Invoke(New DisplayInfoDelegate(AddressOf DisplayStatus), _
                String.Format("Ready(last error: {0}", ex.Message))
        Finally
            isExecuting = False
            If connection IsNot Nothing Then
                connection.Close()
            End If
        End Try
    End Sub
End Class

Comentarios

El método BeginExecuteNonQuery inicia el proceso de ejecución asincrónica de una instrucción de Transact-SQL o un procedimiento almacenado que no devuelve filas, de modo que se puedan ejecutar otras tareas simultáneamente mientras se ejecuta la instrucción.The BeginExecuteNonQuery method starts the process of asynchronously executing a Transact-SQL statement or stored procedure that does not return rows, so that other tasks can run concurrently while the statement is executing. Cuando la instrucción se haya completado, los desarrolladores deben llamar al método EndExecuteNonQuery para finalizar la operación.When the statement has completed, developers must call the EndExecuteNonQuery method to finish the operation. El método BeginExecuteNonQuery vuelve inmediatamente, pero hasta que el código ejecuta la llamada al método EndExecuteNonQuery correspondiente, no debe ejecutar ninguna otra llamada que inicie una ejecución sincrónica o asincrónica en el mismo objeto SqlCommand.The BeginExecuteNonQuery method returns immediately, but until the code executes the corresponding EndExecuteNonQuery method call, it must not execute any other calls that start a synchronous or asynchronous execution against the same SqlCommand object. La llamada a la EndExecuteNonQuery antes de que se complete la ejecución del comando hace que el objeto SqlCommand se bloquee hasta que finalice la ejecución.Calling the EndExecuteNonQuery before the command's execution is completed causes the SqlCommand object to block until the execution is finished.

El parámetro callback permite especificar un delegado de AsyncCallback al que se llama cuando se completa la instrucción.The callback parameter lets you specify an AsyncCallback delegate that is called when the statement has completed. Puede llamar al método EndExecuteNonQuery desde este procedimiento delegado o desde cualquier otra ubicación dentro de la aplicación.You can call the EndExecuteNonQuery method from within this delegate procedure, or from any other location within your application. Además, puede pasar cualquier objeto en el parámetro asyncStateObject, y el procedimiento de devolución de llamada puede recuperar esta información mediante la propiedad AsyncState.In addition, you can pass any object in the asyncStateObject parameter, and your callback procedure can retrieve this information using the AsyncState property.

Tenga en cuenta que el texto y los parámetros del comando se envían al servidor de forma sincrónica.Note that the command text and parameters are sent to the server synchronously. Si se envían comandos grandes o muchos parámetros, este método puede bloquearse durante las operaciones de escritura.If a large command or many parameters are sent, this method may block during writes. Después de enviar el comando, el método vuelve inmediatamente sin esperar una respuesta del servidor; es decir, las lecturas son asincrónicas.After the command is sent, the method returns immediately without waiting for an answer from the server--that is, reads are asynchronous.

Dado que el procedimiento de devolución de llamada se ejecuta desde dentro de un subproceso en segundo plano proporcionado por el Common Language Runtime Microsoft .NET, es muy importante que adopte un enfoque riguroso para controlar las interacciones entre subprocesos desde dentro de sus aplicaciones.Because the callback procedure executes from within a background thread supplied by the Microsoft .NET common language runtime, it is very important that you take a rigorous approach to handling cross-thread interactions from within your applications. Por ejemplo, no debe interactuar con el contenido de un formulario desde el procedimiento de devolución de llamada. Si tiene que actualizar el formulario, debe volver al subproceso del formulario para realizar su trabajo.For example, you must not interact with a form's contents from within your callback procedure; should you have to update the form, you must switch back to the form's thread in order to do your work. En el ejemplo de este tema se muestra este comportamiento.The example in this topic demonstrates this behavior.

Todos los errores que se producen durante la ejecución de la operación se producen como excepciones en el procedimiento de devolución de llamada.All errors that occur during the execution of the operation are thrown as exceptions in the callback procedure. Debe controlar la excepción en el procedimiento de devolución de llamada, no en la aplicación principal.You must handle the exception in the callback procedure, not in the main application. Vea el ejemplo de este tema para obtener información adicional sobre el control de excepciones en el procedimiento de devolución de llamada.See the example in this topic for additional information on handling exceptions in the callback procedure.

Este método omite la propiedad CommandTimeout.This method ignores the CommandTimeout property.

Consulte también:

Se aplica a