randomnumber.aspx.cs

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using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Drawing;
using System.IO;
using System.Drawing.Imaging;

public partial class RandomNumber : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
             
            string str_ValidateCode = GetRandomNumberString(4);

            Session["ValidateCode"] = str_ValidateCode;

            CreateImage(str_ValidateCode);
        }
    }
    public string GetRandomNumberString(int int_NumberLength)
    {
        string str_Number = string.Empty;
        string temp = "";
        string[] source ={"1","2","3","4","5","6","7","8","9",
                           "A","B","C","D","E","F","G","H","I","J","K","L","M","N",
                           "P","Q","R","S","T","U","V","W","X","Y","Z"};
        Random rd = new Random();
        for (int int_index = 0; int_index < int_NumberLength; int_index++)
        {
            str_Number += source[rd.Next(0, source.Length)];
        }

        return str_Number;
    }
    public Color GetRandomColor()
    {
        Random RandomNum_First = new Random((int)DateTime.Now.Ticks);
        
        System.Threading.Thread.Sleep(RandomNum_First.Next(50));
        Random RandomNum_Sencond = new Random((int)DateTime.Now.Ticks);

        
        int int_Red = RandomNum_First.Next(0, 120);
        int int_Green = RandomNum_Sencond.Next(0, 120);
        int int_Blue = (int_Red + int_Green > 400) ? 400 - int_Red - int_Green : 0;
        int_Blue = (int_Blue > 255) ? 120 : int_Blue;

        return Color.FromArgb(int_Red, int_Green, int_Blue);
    }
    public void CreateImage(string str_ValidateCode)
    {
        int int_ImageWidth = str_ValidateCode.Length * 15;
        Random newRandom = new Random();
       
        Bitmap theBitmap = new Bitmap(int_ImageWidth, 20);
        Graphics theGraphics = Graphics.FromImage(theBitmap);
        
        theGraphics.Clear(Color.Bisque);
        
        theGraphics.DrawRectangle(new Pen(Color.Red, 1), 0, 0, int_ImageWidth - 1, 19);

       
        Font theFont = new Font("Arial", 10);

        for (int int_index = 0; int_index < str_ValidateCode.Length; int_index++)
        {
            string str_char = str_ValidateCode.Substring(int_index, 1);
            Brush newBrush = new SolidBrush(GetRandomColor());
            Point thePos = new Point(int_index * 13 + 1 + newRandom.Next(3), 1 + newRandom.Next(3));
            theGraphics.DrawString(str_char, theFont, newBrush, thePos);
        }
       
        MemoryStream ms = new MemoryStream();
         
        theBitmap.Save(ms, ImageFormat.Png);
         
        Response.ClearContent();  
        Response.ContentType = "image/Png";
        Response.BinaryWrite(ms.ToArray());
        theGraphics.Dispose();
        theBitmap.Dispose();
        Response.End();
 

    }
 
    
}