Asp.net (VB.net) generates Verification Code 2

An ASP. NET course is provided to students. Some students asked me how to generate a verification code on the webpage?

I searched the internet and found a lot of web pages, but the code was all the same. I wrote them in C #, because the students only learned VB. net, so I changed C # To form VB. net code:

I use vs. net2005!

First, create a website in vs. net2005.

Add a class named class1.vb with the following content:

Imports Microsoft. VisualBasic

Imports system. Drawing

 

Public class createimage

Public shared sub drawimage ()

Dim IMG as new createimage ()

Httpcontext. Current. Session ("checkcode") = IMG. rndnum (4)

IMG. createimages (httpcontext. Current. Session ("checkcode"). tostring ())

End sub 'drawimage

'/<Summary>

'/Generate verification Image

'/</Summary>

'/<Param name = "checkcode"> Verification character </param>

Private sub createimages (byval checkcode as string)

Dim iwidth as integer = CINT (checkcode. length * 13)

Dim image as new system. Drawing. Bitmap (iwidth, 23)

Dim G as graphics = graphics. fromimage (image)

G. Clear (color. White)

'Define the color

Dim C as color () = {color. Black, color. Red, color. darkblue, color. Green, color. Orange, color. Brown, color. darkcyan, color. Purple}

'Define font

Dim font as string () = {"verdana", "Microsoft sans serif", "Comic Sans MS", "Arial", ""}

Dim rand as new random ()

'Random output noise

Dim I as integer

For I = 0 to 49

Dim X as integer = Rand. Next (image. width)

Dim y as integer = Rand. Next (image. Height)

G. drawrectangle (new pen (color. lightgray, 0), X, Y, 1, 1)

Next I

'Output Verification Code characters of different fonts and colors

For I = 0 to checkcode. Length-1

Dim cIndex as integer = Rand. Next (7)

Dim findex as integer = Rand. Next (5)

Dim F = new system. Drawing. Font (font (findex), 10, system. Drawing. fontstyle. Bold)

Dim B = new system. Drawing. solidbrush (C (cIndex ))

Dim II as integer = 4

If (I + 1) mod 2 = 0 then

II = 2

End if

G. drawstring (checkcode. substring (I, 1), F, B, 3 + I * 12, ii)

Next I

'Draw a border

G. drawrectangle (new pen (color. Black, 0), 0, 0, image. Width-1, image. Height-1)

'Output to the browser

Dim MS as new system. Io. memorystream ()

Image. Save (MS, system. Drawing. imaging. imageformat. JPEG)

Httpcontext. Current. response. clearcontent ()

'Response. clearcontent ();

Httpcontext. Current. response. contenttype = "image/JPEG"

Httpcontext. Current. response. binarywrite (Ms. toarray ())

G. Dispose ()

Image. Dispose ()

End sub 'createimages

'/<Summary>

'/Generate random letters

'/</Summary>

'/<Param name = "vcodenum"> Number of Generated letters </param>

'/<Returns> string </returns>

Private function rndnum (byval vcodenum as integer) as string

Dim allchar as string = "A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, r, S, T, U, V, W, X, Y, Z, 0, 1, 2, 4, 5, 6, 8, 9, A, B, C, D, E, F, g, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, w, x, y, z"

Dim allchararray () as string = allchar. Split (",")

Dim randomcode as string = ""

Dim temp as integer =-1

'Record the last random value and try to avoid producing several identical random numbers.

Dim rand as random = new random

Dim I as integer = 0

Do While (I <vcodenum)

If (temp <>-1) then

Dim key as integer = ctype (datetime. Now. ticks mod system. int32.maxvalue, integer)

'Use system time to generate random Seed

Rand = new random (key)

End if

Dim t as integer = Rand. Next (allchararray. Length) + 1

If T> allchararray. Length-1 then

T = allchararray. Length-1

End if

If temp = t then

I-= 1

Randomcode = Microsoft. VisualBasic. Left (randomcode, I)

End if

Temp = T

Randomcode = randomcode + allchararray (t)

I + = 1

Loop

Return randomcode

End function 'rndnum

End Class 'createimage

Add a webpage named default2.aspx. The Code is as follows:

<% @ Page Language = "VB" autoeventwireup = "false" codefile = "default2.aspx. VB" inherits = "default2" %>

<! Doctype HTML public "-// W 3c // Dtd xhtml 1.0 transitional // en "" http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">

<HTML xmlns = "http://www.w3.org/1999/xhtml">

<Head runat = "server">

<Title> Verification Code Generation </title>

</Head>

<Body>

<Form ID = "form1" runat = "server">

<Div>

<Script language = JavaScript type = "text/JavaScript">

<! __

VaR numkey = math. Random ();

Numkey = math. Round (numkey * 10000 );

Document. Write ("

// __>

</SCRIPT>

</Div>

</Form>

</Body>

</Html>

 

The code file name after the webpage is default2.aspx. VB. The Code is as follows:

Imports createimage

Partial class default2

Inherits system. Web. UI. Page

Protected sub page_load (byval sender as object, byval e as system. eventargs) handles me. Load

Createimage. drawimage ()

End sub

End Class

 

The running effect is as follows: