vb-winforms

Visual Basic Windows Forms Patterns

Modern Windows Forms development with VB.NET focusing on proper UI threading, data binding, and event handling.

Quick Start

' Form definition
Public Class CustomerForm
    Inherits Form

    Private customerService As ICustomerService
    Private bindingSource As New BindingSource()

    Public Sub New()
        InitializeComponent()
        customerService = New CustomerService()
    End Sub

    ' Async load
    Private Async Sub CustomerForm_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Await LoadCustomersAsync()
    End Sub

    Private Async Function LoadCustomersAsync() As Task
        Try
            Cursor = Cursors.WaitCursor
            Dim customers = Await customerService.GetAllAsync()
            bindingSource.DataSource = customers
            dataGridView.DataSource = bindingSource
        Catch ex As Exception
            MessageBox.Show($"Error loading customers: {ex.Message}", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
        Finally
            Cursor = Cursors.Default
        End Try
    End Function
End Class

UI Threading Patterns

Invoke vs BeginInvoke

' Update UI from background thread
Private Sub BackgroundWorker_ProgressChanged(sender As Object, e As ProgressChangedEventArgs)
    ' Already on UI thread with BackgroundWorker
    progressBar.Value = e.ProgressPercentage
    lblStatus.Text = $"Processing: {e.ProgressPercentage}%"
End Sub

' Manual invoke when needed
Private Sub UpdateUIFromThread(text As String)
    If lblStatus.InvokeRequired Then
        lblStatus.Invoke(Sub() lblStatus.Text = text)
    Else
        lblStatus.Text = text
    End If
End Sub

' Async pattern
Private Async Sub btnProcess_Click(sender As Object, e As EventArgs) Handles btnProcess.Click
    btnProcess.Enabled = False
    Try
        Dim result = Await Task.Run(Function() LongRunningOperation())
        lblResult.Text = result  ' Safe - back on UI thread
    Finally
        btnProcess.Enabled = True
    End Try
End Sub