本文整理匯總了VB.NET中System.Data.SqlClient.SqlCommand.BeginExecuteNonQuery方法的典型用法代碼示例。如果您正苦於以下問題:VB.NET SqlCommand.BeginExecuteNonQuery方法的具體用法?VB.NET SqlCommand.BeginExecuteNonQuery怎麽用?VB.NET SqlCommand.BeginExecuteNonQuery使用的例子?那麽, 這裏精選的方法代碼示例或許可以為您提供幫助。您也可以進一步了解該方法所在類System.Data.SqlClient.SqlCommand
的用法示例。
在下文中一共展示了SqlCommand.BeginExecuteNonQuery方法的2個代碼示例,這些例子默認根據受歡迎程度排序。您可以為喜歡或者感覺有用的代碼點讚,您的評價將有助於係統推薦出更棒的VB.NET代碼示例。
示例1: Module1
' 導入命名空間
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
示例2: Form1
' 導入命名空間
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