Generating Registration Image on FLY in asp.net

This article focus on generating image on fly in asp.net. This is very basic functionality which you find on almost all the website which require registration of user. Example: Yahoo Registration require to type you secret string before you can successfully login, this feature has no. of reasons and i am not going into detail of why we want rather i am explaining here how we can. Look for Screenshot for better idea

For demo purpose i am generating image on button click. But generally you require to generate image on page load event of registration form.
Ok back on coding.
Step1: Create a new web application
Step2: Open Code Behind Form of web application you have created.
Step3: Add Namespace for drawing Image.
using System.Drawing;
using System.Drawing.Imaging;
Step4: Write Code for Generating Random Registration String (Here: Generating Random string of 10 in length).
// Generate a random password with the specified length. The password will only
// contain digits and letters (either lowercase or uppercase)
public static string GetRandomPassword(int length)
{
Random rand = new Random();
System.Text.StringBuilder password = new System.Text.StringBuilder(length);
for (int i = 1; i <= length; i++) { int charIndex; // allow only digits and letters do { charIndex = rand.Next(48, 123); } while (!((charIndex >= 48 &&amp;amp; charIndex <= 57) (charIndex >= 65 && charIndex <= 90) (charIndex >= 97 && charIndex <= 122))); // add the random char to the password being built password.Append(Convert.ToChar(charIndex)); } return password.ToString(); }

Step5: Write Code for Generating Image. This code will create RegistrationImg.gif in your application folder.
//Generate Image
private void GenerateImage(string strRegistrationStr)
{
Bitmap objBitmap = new Bitmap(150, 30);
Graphics objGraphics = Graphics.FromImage(objBitmap);

//Fore Color and Background of Image
SolidBrush objForeColor = new SolidBrush(Color.White);
SolidBrush objBackColor = new SolidBrush(Color.Black);

objGraphics.FillRectangle(objBackColor, 0, 0, 150, 30);
//Font settings for Image
Font objFont = new Font("Arial", 15);
//Display from 5point from x-axis and 5point from y-axis
Point objPoint = new Point(5, 5);
//Drawing Registration String
objGraphics.DrawString(strRegistrationStr, objFont, objForeColor, objPoint);
//Saving Registration String as Image
//If you dont want image to save
//objBitmap.Save(Response.OutputStream, ImageFormat.Gif);
//otherwise use this
objBitmap.Save(Server.MapPath("RegistrationImg.gif"), ImageFormat.Gif);
//Release object
if(objBitmap != null)
objBitmap.Dispose();
if (objGraphics != null)
objGraphics.Dispose();
}

Step6: Finally code for calling the created functionality.
protected void btnShowRegistrationImg_Click(object sender, EventArgs e)
{
GenerateImage(GetRandomPassword(10));
ImgRegistrationStr.ImageUrl = "RegistrationImg.gif";
}