Καλημέρα σε όλους !!!
Το πρόβλημα :
Θέλω να εκτελέσω ένα "βαρύ" statement αλλά και να δώσω τη δυνατότητα ακύρωσης στο χρήστη ανά πάσα στιγμή.
Χρησιμοποίησα ένα background thread. 'Ηθελα τη γνώμη σας :
Στο click Event μίας Win form σηκώνω modally μία άλλη (με ένα label με το κλασσικό "Παρακαλώ περιμένετε"
ένα PicureBox με κάποιο animated gif και ένα Cancel button)
Private
Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
Dim MyForm As New frmWait
Try
With DataGrid1
.DataSource = Nothing
.Refresh()
End With
MyForm.ShowDialog(
Me)
With DataGrid1
.DataSource = MyForm.Data
End With
Catch ex As Exception
MsgBox(ex.Message)
Finally
MyForm.Dispose()
End Try
End Sub
Ο κώδικας της frmWait είναι :
Imports
System.Data
Imports System.Data.OleDb
Imports System.Threading
Imports System.Windows.Forms
Public
Class frmWait
Inherits System.Windows.Forms.Form
#
Region " Windows Form Designer generated code "
Public Sub New()
MyBase.New()
'This call is required by the Windows Form Designer.
InitializeComponent()
'Add any initialization after the InitializeComponent() call
End Sub
'Form overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub
'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer
'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
Friend WithEvents Label1 As System.Windows.Forms.Label
Friend WithEvents Button1 As System.Windows.Forms.Button
Friend WithEvents PictureBox1 As System.Windows.Forms.PictureBox
<System.Diagnostics.DebuggerStepThrough()>
Private Sub InitializeComponent()
Dim resources As System.Resources.ResourceManager = New System.Resources.ResourceManager(GetType(frmWait))
Me.Label1 = New System.Windows.Forms.Label
Me.Button1 = New System.Windows.Forms.Button
Me.PictureBox1 = New System.Windows.Forms.PictureBox
Me.SuspendLayout()
'
'Label1
'
Me.Label1.Font = New System.Drawing.Font("Tahoma", 9.75!, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
Me.Label1.Location = New System.Drawing.Point(24, 128)
Me.Label1.Name = "Label1"
Me.Label1.Size = New System.Drawing.Size(157, 16)
Me.Label1.TabIndex = 0
Me.Label1.Text = "Παρακαλώ περιμένετε "
'
'Button1
'
Me.Button1.Location = New System.Drawing.Point(56, 160)
Me.Button1.Name = "Button1"
Me.Button1.Size = New System.Drawing.Size(80, 23)
Me.Button1.TabIndex = 1
Me.Button1.Text = "Ακύρωση"
'
'PictureBox1
'
Me.PictureBox1.Image = CType(resources.GetObject("PictureBox1.Image"), System.Drawing.Image)
Me.PictureBox1.Location = New System.Drawing.Point(40, 16)
Me.PictureBox1.Name = "PictureBox1"
Me.PictureBox1.Size = New System.Drawing.Size(112, 96)
Me.PictureBox1.TabIndex = 2
Me.PictureBox1.TabStop = False
'
'frmWait
'
Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
Me.ClientSize = New System.Drawing.Size(190, 198)
Me.ControlBox = False
Me.Controls.Add(Me.PictureBox1)
Me.Controls.Add(Me.Button1)
Me.Controls.Add(Me.Label1)
Me.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedSingle
Me.Name = "frmWait"
Me.ShowInTaskbar = False
Me.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen
Me.ResumeLayout(False)
End Sub
#
End Region
Private MyDTable As DataTable
Protected Friend Property Data() As DataTable
Get
Data = MyDTable
End Get
Set(ByVal Value As DataTable)
MyDTable = Value
End Set
End Property
Dim MyAsyncThread As Thread
Dim MyAsyncThreadStart As New ThreadStart(AddressOf GetData)
Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Try
If MessageBox.Show("Θέλετε σίγουρα να ακυρώσετε την προεπισκόπηση" + _
"των αποτελεσμάτων;", "Ακύρωση", MessageBoxButtons.YesNo, _
MessageBoxIcon.Question, MessageBoxDefaultButton.Button2, _
MessageBoxOptions.DefaultDesktopOnly) = DialogResult.No Then
Exit Sub
End If
If MyAsyncThread.ThreadState = ThreadState.Background Then
With MyAsyncThread
.Sleep(0)
.Abort()
.Join()
End With
Application.DoEvents()
Me.Data = Nothing
Me.Close()
End If
Catch Aex As ThreadAbortException
MsgBox("Operation aborted")
Catch Eex As ThreadStateException
MsgBox(Eex.Message)
Catch ex As Exception
Throw ex
End Try
End Sub
Private Sub GetData()
Dim MyDataset As New DataSet
Dim MyConnection As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;" + _
"Data Source=C:\Atreus Co ltd\Sinp " + _
"Reporter\Database\TEST.mdb;")
Dim MyAdapter As New OleDbDataAdapter("SELECT * FROM VERY_LARGE_TABLE", _
MyConnection)
Try
MyDataset =
New DataSet
MyConnection.Open()
MyAdapter.Fill(MyDataset, "TEST")
MyConnection.Close()
Me.Data = MyDataset.Tables(0)
Application.DoEvents()
Me.Close()
Catch ex As Exception
Throw ex
Finally
MyAdapter.Dispose()
With MyConnection
.Close()
.Dispose()
End With
End Try
End Sub
Private Sub frmWait_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
MyAsyncThread =
New Thread(MyAsyncThreadStart)
With MyAsyncThread
.IsBackground = True
.Name = "GetDataThread"
.Start()
End With
End Sub
End
Class
Πάνος Αβραμίδης