Visual Basic

Dim startX As Int16
Dim endX As Int16
Dim startY As Int16
Dim endY As Int16
Dim m_Drawing As Boolean
Dim EraserOn As Boolean
Dim MyPen As New Pen(Color.Black)

Private Sub lblPaint_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles lblPaint.Paint
    Dim g As Graphics = e.Graphics
    Dim A, B, X, Y As Integer

    If EraserOn Then
        g.Clear(System.Drawing.Color.White)
        EraserOn = False
        Return
    End If
    If radLine.Checked = True Then
        g.DrawLine(MyPen, New Point(startX, startY), New Point(endX, endY))
    ElseIf radBox.Checked = True Then
        If (endX - startX) >= 0 Then
            A = endX - startX
            X = startX
        Else
            A = startX - endX
            X = endX
        End If
        If (endY - startY) >= 0 Then
            B = endY - startY
            Y = startY
        Else
            B = startY - endY
            Y = endY
        End If
        g.DrawRectangle(MyPen, New Rectangle(X, Y, A, B))
    End If
End Sub

Private Sub lblPaint_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles lblPaint.MouseDown
    If radFree.Checked = True Then
        m_Drawing = True
    End If
    startX = e.X
    startY = e.Y
End Sub

Private Sub lblPaint_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles lblPaint.MouseUp
    endX = e.X
    endY = e.Y
    If m_Drawing = False Then
        lblPaint.Refresh()
    End If
    m_Drawing = False
End Sub

Private Sub lblPaint_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles lblPaint.MouseMove
    If m_Drawing Then
        lblPaint.CreateGraphics().DrawLine(MyPen, startX, startY, e.X, e.Y)
        startX = e.X
        startY = e.Y
    End If
End Sub