I am new to VB.NET. I had programmed in Visual Basic 4 many many years ago. Recently I had to use Visual Studio 2010 to create a quick application for internal usage. Now there was a task which took a long time. As per good user interface design it was obvious that a progress update should be shown to keep the end user informed and updated till the task completed.
To cut a long story short, the requirement was to let the long running task continue while a progress bar showed the progress of the task. After searching for examples, I got a basic idea on how to use threads in VB.Net to accomplish the task I had at hand.
I have attached the VS2010 project for you to download and see the code. The main working parts are explained here.
- Step 1 - Create a basic Windows Form application
- Step 2 - Create a simple Dialog and add a ProgressBar and a Label to it
- Step 3 - Write a method which will launch a separate Thread to perform the long running task
- Step 4 - Write Delegate methods in the Dialog
The code is self explanatory.
Code for the Main Form
Option Explicit On Option Strict On Imports System.Threading ' Main form which launches a long running task and ' shows progress update in a separate dialog Public Class MainForm Inherits Form 'Flag that indcates if a process is running Dim isProcessRunning As Boolean = False 'Progress bar dialog Dim progressDlg As New ProgressDialog 'Long running background process with 'a determinate progress indicator, 'using a seperate modal dialog containing 'a progress bar <MTAThread()> _ Private Sub ButtonClick1_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles ButtonClick1.Click 'If a process is already running, 'warn the user and cancel the operation If isProcessRunning = True Then MessageBox.Show("Sorry, a process is already running.", _ "Status", MessageBoxButtons.OK, _ MessageBoxIcon.Exclamation) Return End If 'Define a background thread and start the 'long running process in this separate thread Dim backgroundThread As _ New Threading.Thread(AddressOf DoLongRunningProcess) ' Start the background process thread backgroundThread.Start() ' Open the dialog progressDlg.Show() End Sub ' The long running process Public Sub DoLongRunningProcess() ' Set the flag that indicates if a ' process is currently running isProcessRunning = True ' Iterate from 0 - 100 ' On each iteration, pause the thread ' for .05 seconds, then update the ' dialog's progress bar For n As Integer = 0 To 100 Thread.Sleep(100) progressDlg.UpdateProgress(n) Next ' Show a dialog box that confirms the process ' has completed MessageBox.Show("Thread completed!", "Status", _ MessageBoxButtons.OK, _ MessageBoxIcon.Information) 'Close the dialog when user clicks OK progressDlg.Close() ' Reset the flag that indicates if a process is ' currently running isProcessRunning = False End Sub End Class
Code for the Progress Dialog
Option Explicit On Option Strict On Imports System.Windows.Forms ' Dialog class with a ProgressBar widget to ' show the progress of a long running task Public Class ProgressDialog Inherits Form ' Delegate to update the progress ' of the ProgressBar widget Delegate Sub DelegateUpdate(ByVal progress As Integer) ' Delegate to handle the Close event ' for this dialog Delegate Sub DelegateClose(ByRef dialog As Form) ' Default constructor which initializes ' this control Public Sub New() InitializeComponent() End Sub ' Method to update the progress bar widget. This ' uses the InvokeRequired and BeginInvoke methods Public Sub UpdateProgress(ByVal progress As Integer) If ProgressBar1.InvokeRequired Then ProgressBar1.BeginInvoke(New DelegateUpdate(AddressOf UpdateDelegateImpl), progress) Else ProgressBar1.Value = progress End If End Sub ' Overloads the Close method Public Overloads Sub Close() If Me.InvokeRequired Then Me.BeginInvoke(New _ DelegateClose(AddressOf CloseDelegateImpl), Me) Else Me.Close() End If End Sub ' Implementation of the DelegateUpdate Sub UpdateDelegateImpl(ByVal progress As Integer) ProgressBar1.Value = progress LabelProgress.Text = "" LabelProgress.Text = progress & CStr("%") End Sub ' Implmentation of the DelegateClose Sub CloseDelegateImpl(ByRef dialog As Form) dialog.Close() End Sub End Class
I have uploaded the project as a ZIP archive on Google Drive. Click to download.