ListBox and ComboBox

Public Class Form1

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ' Add items one at a time
        lstLanguages.Items.Add("Visual Basic 2026")
        lstLanguages.Items.Add("C#")
        lstLanguages.Items.Add("Python")
        lstLanguages.Items.Add("JavaScript")
        lstLanguages.Items.Add("TypeScript")

        ' AddRange is faster for multiple items — adds them all at once
        lstLanguages.Items.AddRange({"Java", "Kotlin", "Swift"})

        ' Select the first item by default
        lstLanguages.SelectedIndex = 0
    End Sub

    Private Sub btnShowSelected_Click(sender As Object, e As EventArgs) Handles btnShowSelected.Click
        If lstLanguages.SelectedIndex = -1 Then
            MsgBox("Please select an item first.", MsgBoxStyle.Exclamation, "No Selection")
            Return
        End If
        lblSelected.Text = $"You selected: {lstLanguages.SelectedItem}"
    End Sub

    Private Sub btnRemove_Click(sender As Object, e As EventArgs) Handles btnRemove.Click
        If lstLanguages.SelectedIndex <> -1 Then
            lstLanguages.Items.RemoveAt(lstLanguages.SelectedIndex)
        End If
    End Sub

    Private Sub btnClear_Click(sender As Object, e As EventArgs) Handles btnClear.Click
        lstLanguages.Items.Clear()
        lblSelected.Text = ""
    End Sub

End Class

' Set at design-time: lstItems.SelectionMode = SelectionMode.MultiExtended

Private Sub btnShowAll_Click(sender As Object, e As EventArgs) Handles btnShowAll.Click
    If lstItems.SelectedItems.Count = 0 Then
        lblResult.Text = "No items selected."
        Return
    End If

    ' Build a comma-separated list of all selected items
    Dim selected As IEnumerable(Of String) =
        lstItems.SelectedItems.Cast(Of String)()

    lblResult.Text = $"Selected ({lstItems.SelectedItems.Count}): {String.Join(", ", selected)}"
End Sub

Public Class Form1

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ' Populate at startup
        cboVersion.Items.AddRange({"VB 2026", "VB 2022", "VB 2019", "VB 2017", "VB 2015", "VB 6"})
        cboVersion.SelectedIndex = 0   ' Default to first item

        ' Auto-complete as user types
        cboVersion.AutoCompleteMode   = AutoCompleteMode.SuggestAppend
        cboVersion.AutoCompleteSource = AutoCompleteSource.ListItems
    End Sub

    Private Sub BtnAdd_Click(sender As Object, e As EventArgs) Handles BtnAdd.Click
        Dim newItem As String = InputBox("Enter new item:", "Add Item")
        If String.IsNullOrWhiteSpace(newItem) Then Return

        If cboVersion.Items.Contains(newItem) Then
            MsgBox($"'{newItem}' already exists in the list.", MsgBoxStyle.Information)
        Else
            cboVersion.Items.Add(newItem)
            cboVersion.SelectedItem = newItem  ' Select the newly added item
        End If
    End Sub

    Private Sub BtnRemove_Click(sender As Object, e As EventArgs) Handles BtnRemove.Click
        Dim itemToRemove As String = InputBox("Enter item to remove:", "Remove Item")
        If cboVersion.Items.Contains(itemToRemove) Then
            cboVersion.Items.Remove(itemToRemove)
        Else
            MsgBox($"'{itemToRemove}' was not found.", MsgBoxStyle.Exclamation)
        End If
    End Sub

    Private Sub cboVersion_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cboVersion.SelectedIndexChanged
        ' Fires every time the selection changes
        lblSelected.Text = $"You chose: {cboVersion.SelectedItem}  (index {cboVersion.SelectedIndex})"
    End Sub

End Class

Public Class TaskManager

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Me.Text = "Task Manager"
        ' Pre-load some sample tasks
        lstTasks.Items.AddRange({"Buy groceries", "Finish VB 2026 lesson", "Call the dentist"})
        UpdateTaskCount()
    End Sub

    Private Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click
        Dim task As String = txtTask.Text.Trim()

        If String.IsNullOrEmpty(task) Then
            lblStatus.ForeColor = Color.Red
            lblStatus.Text = "⚠ Please enter a task."
            Return
        End If

        If lstTasks.Items.Contains(task) Then
            lblStatus.ForeColor = Color.OrangeRed
            lblStatus.Text = "⚠ This task already exists."
            Return
        End If

        lstTasks.Items.Add(task)
        txtTask.Clear()
        txtTask.Focus()
        lblStatus.ForeColor = Color.DarkGreen
        lblStatus.Text = $"✔ Added: {task}"
        UpdateTaskCount()
    End Sub

    Private Sub btnRemove_Click(sender As Object, e As EventArgs) Handles btnRemove.Click
        If lstTasks.SelectedIndex = -1 Then
            lblStatus.ForeColor = Color.OrangeRed
            lblStatus.Text = "⚠ Select a task to remove."
            Return
        End If
        Dim removed As String = lstTasks.SelectedItem.ToString()
        lstTasks.Items.RemoveAt(lstTasks.SelectedIndex)
        lblStatus.ForeColor = Color.Gray
        lblStatus.Text = $"Removed: {removed}"
        UpdateTaskCount()
    End Sub

    Private Sub btnClear_Click(sender As Object, e As EventArgs) Handles btnClear.Click
        lstTasks.Items.Clear()
        lblStatus.ForeColor = Color.Gray
        lblStatus.Text = "All tasks cleared."
        UpdateTaskCount()
    End Sub

    ' Helper — keeps the task count label updated
    Private Sub UpdateTaskCount()
        lblCount.Text = $"Tasks: {lstTasks.Items.Count}"
    End Sub

    ' Press Enter in the TextBox to trigger Add
    Private Sub txtTask_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtTask.KeyPress
        If e.KeyChar = Chr(13) Then btnAdd.PerformClick()
    End Sub

End Class

Imports System.ComponentModel

Public Class Form1

    ' BindingList automatically reflects changes back to the ListBox
    Private _tasks As New BindingList(Of String)

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        _tasks.Add("Buy groceries")
        _tasks.Add("Finish VB 2026 lesson")
        _tasks.Add("Call the dentist")

        ' Bind the list directly — no Items.Add() loop needed
        lstTasks.DataSource = _tasks
    End Sub

    Private Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click
        ' Add to the BindingList — ListBox updates automatically!
        _tasks.Add(txtTask.Text.Trim())
        txtTask.Clear()
    End Sub

    Private Sub btnRemove_Click(sender As Object, e As EventArgs) Handles btnRemove.Click
        If lstTasks.SelectedIndex >= 0 Then
            _tasks.RemoveAt(lstTasks.SelectedIndex)
        End If
    End Sub

    ' Filter with LINQ — bind filtered results to a second ListBox
    Private Sub txtSearch_TextChanged(sender As Object, e As EventArgs) Handles txtSearch.TextChanged
        Dim filtered = _tasks.Where(Function(t) t.ToLower().Contains(txtSearch.Text.ToLower())).ToList()
        lstFiltered.DataSource = filtered
    End Sub

End Class