Автоматическое изменение размеров ListBox

    Public Sub SetListBoxAutoSize(listBox As ListBox)
        If listBox.Items.Count = 0 Then Exit Sub
        Dim itemBigWidth As String = String.Empty
        Dim EndWidth As Integer = -1
        For Each item As String In listBox.Items
            If item.Length > EndWidth Then itemBigWidth = item : EndWidth = item.Length
        Next
        Dim TSize As Size = TextRenderer.MeasureText(itemBigWidth, listBox.Font)
        listBox.Size = New Size(TSize.Width + 4, TSize.Height * (listBox.Items.Count + 1))
    End Sub

Public Class Form1
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        SetListBoxAutoSize(ListBox1)
    End Sub
 
    Public Sub SetListBoxAutoSize(listBox As ListBox)
        If listBox.Items.Count = 0 Then Exit Sub
        Dim itemBigWidth As String = String.Empty
        Dim EndWidth As Integer = -1
        For Each item As String In listBox.Items
            If item.Length > EndWidth Then itemBigWidth = item : EndWidth = item.Length
        Next
        Dim TSize As Size = TextRenderer.MeasureText(itemBigWidth, listBox.Font)
        listBox.Size = New Size(TSize.Width + 4, TSize.Height * (listBox.Items.Count + 1))
    End Sub
End Class