VB.NET 异步读取数据方法之二

Imports System.Data.SqlClient

Imports System.Threading

Public Class FrmMain

Private Sub btnLoad_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLoad.Click

Dim cn As New SqlConnection ’定义连结字符串，并且要注意加ASYNCHRONOUS PROCESSING=TRUE

cn.ConnectionString = "Data Source=WANGLI;Initial Catalog=PlcData;Persist Security Info=True;User ID=sa;pwd=sa;Asynchronous processing=true"

cn.Open()

Dim strSql As String = "select * from tbdata"

Dim mycommand As New SqlCommand(strSql, cn)

Dim itfAsynch As IAsyncResult ’定义一个异步读取变量

itfAsynch = mycommand.BeginExecuteReader(CommandBehavior.CloseConnection) ’执行异步读写

While Not itfAsynch.IsCompleted ’ 等待执行,

Console.WriteLine("Working on main thread...")

Thread.Sleep(1000)

End While

Console.WriteLine()

Dim dt As New DataTable ’执行完结后将数据写入datatable中

Dim MydataReader As SqlDataReader = mycommand.EndExecuteReader(itfAsynch)

'While MydataReader.Read

' Console.WriteLine("序号:" & MydataReader(0).ToString)

'End While

dt.Load(MydataReader)

DataGridView1.DataSource = dt

MydataReader.Close()

Console.ReadLine()

End Sub

End Class