Making thumbnail dynamically with ashx file in asp.net

In this article I am going to show how to resize image dynamically or making thumbnail dynamically with ashx file.Start new website project give name thumbnail.In menu go to Webite > Add new item and select Generic Handler. Name it Handler.ashx, You will get auto generated code in it like given below:

<%@ WebHandler Language="C#" Class="Handler" %>

using System;
using System.Web;

public class Handler : IHttpHandler {

public void ProcessRequest (HttpContext context) {
context.Response.ContentType = "text/plain";
context.Response.Write("Hello World");
}

public bool IsReusable {
get {
 return false;
}
}

}


Now add given namespace to handle the image files
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;

Make a new folder for images files, name it images. Put some images in this folder.

Now our next step is getting the height , width , image name and changing image size.
To do these things, here query string is used. In ProcessRequest method write follwing lines.

public class Handler : IHttpHandler {

public void ProcessRequest (HttpContext context) {
// for new height of image
int h=int.Parse(context.Request.QueryString["h"].ToString());
// for new width of image
int w = int.Parse(context.Request.QueryString["w"].ToString());
// for  image file name
string file = context.Request.QueryString["file"].ToString();

// Path of image folder where images files are placed
string  filePath = context.Server.MapPath("~/images/" + file);

// Resize proccess
using(System.Drawing.Image img=System.Drawing.Image.FromFile(filePath))
{
Bitmap objBmp = new Bitmap(img,w, h);
string extension = Path.GetExtension(filePath);
MemoryStream ms;
byte[] bmpBytes;
switch (extension.ToLower())
{
  case ".jpg":
  case ".jpeg":
      ms = new MemoryStream();
      objBmp.Save(ms, ImageFormat.Jpeg);
      bmpBytes = ms.GetBuffer();
      context.Response.ContentType = "image/jpeg";
      context.Response.BinaryWrite(bmpBytes);
      objBmp.Dispose();
      ms.Close();
      context.Response.End();
      break;
  case ".png":
        ms = new MemoryStream();
        objBmp.Save(ms, ImageFormat.Png);
        bmpBytes = ms.GetBuffer();
       context.Response.ContentType = "image/png";
       context.Response.BinaryWrite(bmpBytes);
       objBmp.Dispose();
       ms.Close();
       context.Response.End();
  break;
 case ".gif":
      ms = new MemoryStream();
      objBmp.Save(ms, ImageFormat.Gif);
      bmpBytes = ms.GetBuffer();
      context.Response.ContentType = "image/png";
      context.Response.BinaryWrite(bmpBytes);
      objBmp.Dispose();
      ms.Close();
      context.Response.End();
      break;

}
img.Dispose();
}

}

Now we move to Default.aspx page, drag here  Image tool from tool box :

For retriving the image set ImageUrl as given below with height width and image name.

And now finally run the default.aspx and see the result.