SqlCommand.BeginExecuteNonQuery Metod

Källa:

System.Data.SqlClient.notsupported.cs

public:
 IAsyncResult ^ BeginExecuteNonQuery();

public IAsyncResult BeginExecuteNonQuery();

member this.BeginExecuteNonQuery : unit -> IAsyncResult

Public Function BeginExecuteNonQuery () As IAsyncResult

Returer

En IAsyncResult som kan användas för att avsöka eller vänta på resultat, eller båda. Det här värdet behövs också när du anropar EndExecuteNonQuery(IAsyncResult), som returnerar antalet berörda rader.

Undantag

Exempel

Följande konsolprogram skapar uppdateringsdata i AdventureWorks-exempeldatabasen och utför sitt arbete asynkront. För att emulera en tidskrävande process infogar det här exemplet en WAITFOR-instruktion i kommandotexten. Normalt sett skulle du inte göra något för att få kommandona att köras långsammare, men om du gör det i det här fallet blir det enklare att demonstrera det asynkrona beteendet.

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

Kommentarer

Metoden BeginExecuteNonQuery startar processen med att asynkront köra en Transact-SQL-instruktion eller lagrad procedur som inte returnerar rader, så att andra aktiviteter kan köras samtidigt medan instruktionen körs. När instruktionen har slutförts måste utvecklare anropa EndExecuteNonQuery metoden för att slutföra åtgärden. Metoden BeginExecuteNonQuery returnerar omedelbart, men tills koden kör motsvarande EndExecuteNonQuery metodanrop får den inte köra några andra anrop som startar en synkron eller asynkron körning mot samma SqlCommand objekt. EndExecuteNonQuery Om du anropar innan kommandots körning har slutförts blockeras SqlCommand objektet tills körningen är klar.

Observera att kommandotexten och parametrarna skickas synkront till servern. Om ett stort kommando eller många parametrar skickas kan den här metoden blockeras under skrivningar. När kommandot har skickats returnerar metoden omedelbart utan att vänta på ett svar från servern, dvs. läsningar är asynkrona.

Eftersom den här överlagringen inte stöder en återanropsprocedur måste utvecklare antingen avsöka för att avgöra om kommandot har slutförts med IsCompleted hjälp av egenskapen för den IAsyncResult som returneras av BeginExecuteNonQuery metoden eller vänta tills ett eller flera kommandon har slutförts med egenskapen AsyncWaitHandle för den returnerade IAsyncResult.

Den här metoden ignorerar egenskapen CommandTimeout .

Se även

• Ansluta och hämta data i ADO.NET
• Använder .NET Framework Data Provider för SQL Server
• översikt över ADO.NET

Källa:

System.Data.SqlClient.notsupported.cs

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

Parametrar

Returer

En IAsyncResult som kan användas för att avsöka eller vänta på resultat, eller båda. Det här värdet behövs också när du anropar EndExecuteNonQuery(IAsyncResult), som returnerar antalet berörda rader.

Undantag

Exempel

Följande Windows-program visar användningen av metoden BeginExecuteNonQuery och kör en Transact-SQL-instruktion som innehåller en fördröjning på flera sekunder (emulering av ett tidskrävande kommando).

Det här exemplet visar många viktiga tekniker. Detta inkluderar att anropa en metod som interagerar med formuläret från en separat tråd. Dessutom visar det här exemplet hur du måste blockera användare från att köra ett kommando flera gånger samtidigt och hur du måste se till att formuläret inte stängs innan återanropsproceduren anropas.

Om du vill konfigurera det här exemplet skapar du ett nytt Windows-program. Placera en Button kontroll och en Label kontroll i formuläret (acceptera standardnamnet för varje kontroll). Lägg till följande kod i formulärets klass och ändra reťazec pripojenia efter behov för din miljö.

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
Imports System.Windows.Forms

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 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

Kommentarer

Metoden BeginExecuteNonQuery startar processen med att asynkront köra en Transact-SQL-instruktion eller lagrad procedur som inte returnerar rader, så att andra aktiviteter kan köras samtidigt medan instruktionen körs. När instruktionen har slutförts måste utvecklare anropa EndExecuteNonQuery metoden för att slutföra åtgärden. Metoden BeginExecuteNonQuery returnerar omedelbart, men tills koden kör motsvarande EndExecuteNonQuery metodanrop får den inte köra några andra anrop som startar en synkron eller asynkron körning mot samma SqlCommand objekt. EndExecuteNonQuery Om du anropar innan kommandots körning har slutförts blockeras SqlCommand objektet tills körningen är klar.

Med callback parametern kan du ange ett AsyncCallback ombud som anropas när -instruktionen har slutförts. Du kan anropa EndExecuteNonQuery metoden inifrån den här ombudsproceduren eller från någon annan plats i ditt program. Dessutom kan du skicka valfritt objekt i parametern asyncStateObject och återanropsproceduren kan hämta den här informationen med hjälp av AsyncState egenskapen .

Observera att kommandotexten och parametrarna skickas synkront till servern. Om ett stort kommando eller många parametrar skickas kan den här metoden blockeras under skrivningar. När kommandot har skickats returnerar metoden omedelbart utan att vänta på ett svar från servern, dvs. läsningar är asynkrona.

Eftersom återanropsproceduren körs inifrån en bakgrundstråd som tillhandahålls av Microsoft .NET common language runtime, är det mycket viktigt att du använder en rigorös metod för att hantera interaktioner mellan trådar inifrån dina program. Du får till exempel inte interagera med ett formulärs innehåll inifrån återanropsproceduren. om du måste uppdatera formuläret måste du växla tillbaka till formulärets tråd för att kunna utföra ditt arbete. Exemplet i det här avsnittet visar det här beteendet.

Alla fel som uppstår under körningen av åtgärden utlöses som undantag i återanropsproceduren. Du måste hantera undantaget i återanropsproceduren, inte i huvudprogrammet. Mer information om hur du hanterar undantag i återanropsproceduren finns i exemplet i det här avsnittet.

Den här metoden ignorerar egenskapen CommandTimeout .

Se även

• Ansluta och hämta data i ADO.NET
• Använder .NET Framework Data Provider för SQL Server
• översikt över ADO.NET