VB.NET OverflowException未处理

Question

I have a problem in VB 2008 that gives me an error: " OverflowException was unhandled. " in that piece of code: The error is highlights the Next b

        Dim gfx As Graphics
        Dim a,r,g,b As byte
        Dim left As Integer
        Dim lStep As Integer = 1

        For left = 0 To Me.ClientRectangle.Height Step lStep

            For a = 1 To 255
                For r = 1 To 255
                    For g = 1 To 255
                        For b = 1 To 255
                            gfx.DrawLine(New Pen(Color.FromArgb(a, r, g, b)), 0, left, Me.ClientRectangle.Width, left)

                        Next b

                    Next g
                Next r
            Next a

Answer 1

    Dim a,r,g,b As byte

That's where your problem started. Your For loops increment from 1 to 255, stopping when the value reaches 256. But that is not possible for a Byte, it can only store a value between 0 and 255. Kaboom when the Next statement tries to increment it from 255 to 256.

Simply declare them As Integer . It not only solves the overflow problem, it is also faster.