Idea is to build a URL, make an HTTP request and download the QR Code image. Result is the following image:

HTTP Request

URL looks like http://www.esponce.com/api/v3/generate?content={content}&format={format} where {content} is URL encoded content to be embedded in QR and {format} is output image format. Available formats are png, jpg, bmp, tif, xaml, svg, eps, txt, html, zip (containing all listed formats)

List of other parameters like color and size can be found here.

C# Sample

This code can be used in .NET 2.0 including ASP.NET and WPF or Silverlight for web or WP7

using System;
using System.IO;
using System.Web;
using System.Net;

public class Program
{
  public static void Main(string[] args)
  {
    //Generate a QR Code and save it to file "sample.png"
    Generate("your content goes here", "png", "sample.png");
  }

  public static void Generate(string content, string format, string path)
  {
    string encoded = HttpUtility.UrlEncode(content);
    Uri uri = new Uri("http://www.esponce.com/api/v3/generate?content=" + encoded + "&format=" + format);
    WebClient client = new WebClient();
    client.DownloadFile(uri, path);
  }
}

Java Sample

This code can be used in a classic Java application or web applet or Android application

import java.io.*;
import java.net.*;

public class qrcode
{
  public static void main(String args[])
  {
    //Generate a QR Code image and save it to file "sample.png"
    generate("your content goes here", "png", "sample.png");
  }

  public static void generate(String content, String format, String path)
  {
    try
    {
      String encoded = URLEncoder.encode(content, "UTF-8");
      String url = "http://www.esponce.com/api/v3/generate?content=" + encoded + "&format=" + format;
      BufferedInputStream ins = new BufferedInputStream(new URL(url).openStream());
      FileOutputStream fos = new FileOutputStream(path);
      BufferedOutputStream bos = new BufferedOutputStream(fos, 1024);

      int size = 0;
      byte data[] = new byte[1024];
      while ((size = ins.read(data, 0, 1024)) > 0)
      {
        bos.write(data, 0, size);
      }

      bos.close();
      fos.close();
      ins.close();
    }
    catch (Exception e)
    {
    }
  }
}

Python Sample

Using Python 2.7

#!/usr/bin/env python
# -*- coding: UTF-8 -*-

import urllib
import httplib

def generate(content, format = "png"):
    query = urllib.urlencode({ "content": content, "format": format })
    con = httplib.HTTPConnection("www.esponce.com")
    con.request("GET", "/api/v3/generate?" + query)
    response = con.getresponse()
    image = response.read()
    con.close()
    return image

image = generate("your content goes here")
file = open("sample.png", "wb")
file.write(image)
file.close()

JavaScript Sample

JavaScript in combination with HTML

<img id="qrcode" src="" alt="QR Code" />
<script type="text/javascript">
    function generate(content)
    {
        var url = "http://www.esponce.com/api/v3/generate?content=" + encodeURI(content) + "&format=png";
        var img = document.getElementById("qrcode");
        img.src = url;
    }
    generate("your content goes here");
</script>

PHP Sample

<img src="<?php echo generate("your content goes here"); ?>" alt="QR Code" />

<?php
function generate($content, $format = "png")
{
    $encoded = urlencode($content);
    $url = "http://www.esponce.com/api/v3/generate?content=$encoded&format=$format";
    return $url;
}
?>

There is more

Download all samples with make script here.

Other QR Code related methods like decoding (reverse process of generating) and tracking scans can be found at esponce.com.

It is possible so you need to use IIS system program appcmd.exe (you can find it in C:\Windows\System32\inetsrv\ (we suggest you to put this into your PATH variable)

Adding additional bindings

You want to add your-subdomain.your-domain.com binding to your IIS 7 app named your-domain.com

C:\Windows\System32\inetsrv\appcmd set site /site.name: your-domain.com /+bindings.[protocol='http',bindingInformation='*:80:your-subdomain.your-domain.com']

Removing existing bindings

You want to remove your-subdomain.your-domain.com binding from your IIS 7 app named your-domain.com (please notice - sign in front of bindings word)

C:\Windows\System32\inetsrv\appcmd set site /site.name: your-domain.com /-bindings.[protocol='http',bindingInformation='*:80:your-subdomain.your-domain.com']

And that’s it but if you want to run it from ASP.NET you could try to use Process and ProcessInfo classes to run DOS command but there are some permissions problems (we didn’t investigated much).

Other (alternative way that we tried is directly from the code)
You will need to reference this DLL: c:\Windows\System32\inetsrv\Microsoft.Web.Administration.dll

using (ServerManager serverManager = new ServerManager())
{
  if (serverManager.Sites == null)
    throw new SimpleException("There are no IIS applications!");

  var esponceApp = serverManager.Sites.FirstOrDefault(
x => x.Name == Settings.IISAppName);
  if (esponceApp != null)
  {
    BindingCollection bindingCollection = esponceApp.Bindings;
    Binding binding = bindingCollection.CreateElement("binding");
    binding["protocol"] = "http";
    binding["bindingInformation"] =
string.Format(@"{0}:{1}:{2}", "*", "80", this.DomainName);

    //Remove this binding if already exists.
    int oldBindingIndex = -1;
    int bindingIndex = -1;
    foreach (Binding currentBinding in esponceApp.Bindings)
    {
      if (currentBinding.BindingInformation ==
binding["bindingInformation"].ToString())
      {
        bindingIndex = esponceApp.Bindings.IndexOf(currentBinding);
      }
      if (!string.IsNullOrEmpty(oldDomainName) &&
      currentBinding.BindingInformation ==
string.Format(@"{0}:{1}:{2}", "*", "80", oldDomainName))
      {
        oldBindingIndex = esponceApp.Bindings.IndexOf(currentBinding);
      }
    }
    if (bindingIndex != -1)
    {
      esponceApp.Bindings.RemoveAt(bindingIndex);
    }
    if (oldBindingIndex != bindingIndex && oldBindingIndex != -1)
    {
      esponceApp.Bindings.RemoveAt(oldBindingIndex);
    }

    //Add this bindings
    bindingCollection.Add(binding);
    serverManager.CommitChanges();
  }
}
}
catch
{
throw new SimpleException("Could not add binding into IIS application!");
}

Important!
Set identity of your app’s Application Domain from Advanced Settings > Process Model > Identity > Change “ApplicationPoolIdentity” to “Local System”

Investigate also security implications if you are not running this in Intranet….

HttpCookie cookie = new HttpCookie(this.Name);
cookie.Expires = DateTime.UtcNow.AddMonths(-1);
HttpContext.Current.Response.Cookies.Add(cookie);

Server cannot modify cookies after HTTP headers have been sent.

After searching and searching if we have somewhere Response.Write in or ASP.NET MVC code we found out that we don’t have such things.
Suddenly, we found out that we played with Session object (trying to clear it) before deleting Cookie and that was it. Reordering these operations solved our problem.

Update on this case

It already went over simple generator functionality and new features are adding.

QR Codes Generator and API

Basically, beside QR Code generation, we are offering as addition:

• Tracking of generated QR Codes – for marketing managers ti know which locations work best (i.e. posters with printed QR Code)
• Dynamic QR Codes – if some QR Code is already printed you can make it point to completely different URL without changing the printed code
• Adding your logo inside QR Code (with readability testing) – branding feature
• All types of content are supported (hyperlinks, custom text, vCard, Bizcard, Mecard,  vCalendar, social networks – Twitter, Facebook, YouTube, Geo locations and maps, SMS messages, phones,…)
• Strong use of API – automating generation process and possibility to use from your application/website – this is what we will talk about a little bit more in this article…

Using API is not complicated at all, we wrote a tutorial which is easy to understand.

Here is an example how you can have instantly QR Code image on your website:

This are direct links:

• Hello World custom text
• Google Maps location of company’s office
• QR Code generator URL

This how it could look like inside your website (just put this hyperlink inside your IMG tag)

<img src="http://qrcode.good-survey.com/api/v2/generate?content=
http%3a%2f%2fmaps.google.com%2fmaps%3ff%3dq%26q%3d46.043286%2c14.492791300000022%
26q%3d30%2bTeslova%2bUlica%252c%2bLjubljana%2b1000%252c%2bSlovenia&
format=png&padding=2&size=10&em=byte&ec=m" alt="Avivo location" />

using System;
using System.Collections.Generic;
using System.Data;
using System.Text;
using System.Web.Mvc;

namespace Avivo.Web.Common
{
  public static class ModelStateDictionaryExtensions
  {
    /// <summary>
    /// Copy validation message from one field to another
    /// </summary>
    /// <param name="modelState">model state</param>
    /// <param name="source">field to copy from</param>
    /// <param name="target">field to copy to</param>
    public static void CopyMessage(this ModelStateDictionary modelState, string source,
      string target)
    {
      if (modelState.ContainsKey(source) && modelState.Errors.Count > 0)
      {
        modelState.AddModelError(target, modelState.Errors[0].ErrorMessage);
      }
    }
  }
}

So, whenever an error occurs, you would like to show a custom 404 error page in ASP.NET MVC? This blog post describes how to techically handle and display error page effectively. Reader should have some basic knowledge of setting IIS and ASP .NET MVC project.

Error page is displayed when something goes wrong. Page should inform user about what happened and what he or she should do next. Page should also inform bots, crawlers, spiders not to search any relevent content in there, e.g. Google won’t display error page as search result. This is handled with HTTP status code known as 404. There are also other HTTP status codes for specific problems, e.g. for maintenance, for restricted access…

Create action and view

First, create a friendly page for user and set indicator for bots not to handle this page as obvious page. In this case “Main” controller with “Error” action. Note for IE 5,6: error page should have content larger than 512 bytes otherwise IE will display its own content.

public class MainController
{
  public ActionResult Error()
  {
    //404 - Tell search engine not to display this page on search results
    Response.StatusCode = 404;
    Response.StatusDescription = "Not Found";
    return View();
  }
}

Register route that eats anything

Open Global.asax(.cs) in the MVC project and register error page route. Rule should be designed to capture all requests that do not fit in previous route rules. Simple solution: {*anything} rule captures any path including slashes, e.g. /shop/mushrooms-123.

//Somewhere in Global.asax
public static void RegisterRoutes(RouteCollection routes)
{
  //Registered routes
  //...

  //Error route should be registered last
  routes.MapRoute
  (
    "ErrorPage",
    "{*anything}",
    new { controller = "Main", action = "Error" }
  );
}

Advantage: no redirects, requested URL string should be kept in browser’s location bar. For example, when
user requests /shop/mushrooms-123 in browser the error page content will be display but the URL will remain original.
The opposite of redirecting and displaying /error in location bar.

How to handle other errors?

Other errors in ASP .NET can be handled in Application_Error method in Global.asax.

//Somewhere in Global.asax
protected void Application_Error()
{
  //Useful for debugging to get error details
  Exception ex = Server.GetLastError();

  //Redirect to error page
  //Can be "/Main/Error" or "/error" or other route as "ErrorPage" rule eats all
  Response.Redirect(Request.ApplicationPath + "/error/500");
}

Configuration in IIS 7.5

1. Open IIS Manager. Shortcut: click Start in Windows, type “inetmgr” in search box then press Enter.
2. Click on a website on the left side.
3. Select Error Pages on the right side.
4. Configure scenarios for specific status codes, as displayed on screenshots.

Troubleshooting

Q: Browser displays system error page when I expect custom error page.
A: Configure Error Pages for the website in IIS. Error Pages may differ between websites.

Q: Error handling is defined in web.config but does not work in Windows Server 2008.
A: Try to edit Error Pages directly in IIS (IIS Manager -> Sites -> (website name) -> Error Pages)

Q: Status code 200 OK displays a custom error page but 404 Not Found displays generic IIS error page (yellow box with techical message)
A: Configure Error Pages (see above). “customErrors” in web.config may not work as expected.

Q: Can I keep status 200 OK to display error page?
A: It will do the job for users who visually see and understand the content, but may not work for bots (i.e. displaying error page in search result)