asp.net Generate picture Verification code

Create a new getcode.aspx page and glue the following code to the GetCode.aspx.cs code file

Using System;
Using System.Collections;
Using System.Configuration;
Using System.Data;
Using System.Web;
Using System.Web.Security;
Using System.Web.UI;
Using System.Web.UI.HtmlControls;
Using System.Web.UI.WebControls;
Using System.Web.UI.WebControls.WebParts;

Using System.Drawing;
Using System.Drawing.Drawing2D;

public partial class WebControl_GetCode:System.Web.UI.Page
{
const int number = 5;
String checkcode = "";
protected void Page_Load (object sender, EventArgs e)
{
Checkcode = "";
Drawstr (RandomString ());
session["GetCode"] = Checkcode;
}

Used to generate random letters and numbers.
private String RandomString ()
{
String str = "2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,j,k,l,m,n,p,q,r,s,t,u,v,w,x,y,z";
string[] Strarray = str. Split (",");
String codestr = "";
Random ran = new Random ();
string s = "";
for (int i = 0; i < number; i++)
{
s = Strarray[ran. Next (30)];
Checkcode = s;
Codestr + = "" + S;
}
Codestr + = "";
return codestr;
}

Drawing
private void Drawstr (string codestr)