Visual Basic

backgroundworker1.cancleasync()

Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        For Each ctl As Control In Me.Controls
            If TypeOf ctl Is Button Then
                If ctl.Text.Length = 1 Then
                    AddHandler ctl.Click, AddressOf btnKey_Click
                End If
            End If
        Next
    End Sub

    Private Sub btnKey_Click(ByVal sender As Object, ByVal e As System.EventArgs)
        TextBox1.Focus()
        SendKeys.Send(sender.text)
        
    End Sub

End Class