Async Await

Imports System.ComponentModel

Public Class FrmSQL

    Dim sw As New Stopwatch()

    Public Async Function LoadDTAsync() As Task
        Dim cDB As New CDataBase
        Dim tasks As New List(Of Task(Of DataTable))
        Await Task.Run(Sub()
                           For i = 0 To 5
                               tasks.Add(cDB.LoadDTDataAdapterAsync())
                               Task.Delay(25)
                           Next
                       End Sub)
        Dim results = Await Task.WhenAll(tasks)
        For i = 0 To results.Length - 1
            DirectCast(Controls("DGV" & i + 1), DataGridView).DataSource = results(i)
        Next
    End Function

    Private Async Sub BtnTask_Click(sender As Object, e As EventArgs) Handles BtnTask.Click
        Label1.Text = ""
        sw.Reset()
        sw.Start()
        For i = 0 To 5
            DirectCast(Controls("DGV" & i + 1), DataGridView).DataSource = Nothing
        Next

        Await LoadDTAsync()
        Label1.Text = String.Format("{0:00}s : {1:00}ms", sw.Elapsed.Seconds, sw.Elapsed.Milliseconds)
        sw.Stop()
    End Sub

    Private Sub BtnBgw_Click(sender As Object, e As EventArgs) Handles BtnBgw.Click
        For i = 0 To 5
            DirectCast(Controls("DGV" & i + 1), DataGridView).DataSource = Nothing
        Next
        Label1.Text = ""
        sw.Reset()
        sw.Start()
        If Not Bgw.IsBusy Then
            Bgw.RunWorkerAsync()
        End If
    End Sub

    Private Sub Bgw_DoWork(sender As Object, e As DoWorkEventArgs) Handles Bgw.DoWork
        Dim lstDT As New List(Of DataTable)
        Dim asd As New CDataBase
        For i = 0 To 5
            lstDT.Add(asd.LoadDTDataAdapter)
        Next
        e.Result = lstDT
    End Sub

    Private Sub Bgw_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles Bgw.RunWorkerCompleted
        Dim lstDT As List(Of DataTable) = e.Result
        For i = 0 To lstDT.Count - 1
            DirectCast(Controls("DGV" & i + 1), DataGridView).DataSource = lstDT(i)
        Next
        Label1.Text = String.Format("{0:00}s : {1:00}ms", sw.Elapsed.Seconds, sw.Elapsed.Milliseconds)
        sw.Stop()
    End Sub
End Class

Public Class CDataBase

    Public Async Function LoadDTDataAdapterAsync() As Task(Of DataTable)
        Using con As New SqlClient.SqlConnection("Server=(local);Database=dummy;Trusted_Connection=True;")
            Using adp As New SqlClient.SqlDataAdapter("select * from tblAuthors", con)
                Using DT As New DataTable
                    Await Task.Run(Sub() adp.Fill(DT))
                    Return DT
                End Using
            End Using
            End Using
    End Function

    Public Function LoadDTDataAdapter() As DataTable
        Using con As New SqlClient.SqlConnection("Server=(local);Database=dummy;Trusted_Connection=True;")
            Using adp As New SqlClient.SqlDataAdapter("select * from tblAuthors", con)
                Using DT As New DataTable
                    adp.Fill(DT)
                    Return DT
                End Using
            End Using
        End Using
    End Function
End Class