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.

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

Ideas

• using Canvas and positioning items with absolute coordinates – items are always fixed, coordinates need to be calculated, so it is the least flexible approach, no
• using StackPanel with items that have margin – margins need to be recalculated when an item is added or removed or when container is resized, maybe
• using Grid with predefined rows and columns – notice predefined, means less flexibility, but offers equal size rows/columns, maybe
• using a custom control – making Grid more dynamic but extending number of rows/columns when items are added, yes

Custom Control: EqualDistanceStackPanel

As written before, custom control should extend Grid to become more flexible

public class EqualDistanceStackPanel : Grid
{
}

EqualDistanceStackPanel should implement ItemsSource and ItemTemplate just like ItemsControl

#region ItemsSource
public IEnumerable ItemsSource
{
  get { return (IEnumerable)GetValue(ItemsSourceProperty); }
  set { SetValue(ItemsSourceProperty, value); }
}

public static readonly DependencyProperty ItemsSourceProperty =
  DependencyProperty.Register("ItemsSource", typeof(IEnumerable),
  typeof(EqualDistanceStackPanel), new PropertyMetadata(ItemsSourceChanged));

private static void ItemsSourceChanged(DependencyObject d,
  DependencyPropertyChangedEventArgs e)
{
  var panel = d as EqualDistanceStackPanel;
  if (panel != null)
  {
    if (e.OldValue != null)
    {
      panel.ClearItems();
    }
    if (e.NewValue != null)
    {
      panel.BindItems(e.NewValue as IEnumerable);
    }
  }
}
#endregion

public DataTemplate ItemTemplate
{
  get;
  set;
}

ClearItems method deletes all previous elements from the panel and BindItems attaches fresh controls from item template.

protected void ClearItems()
{
  this.Children.Clear();
}

protected void BindItems(IEnumerable items)
{
  if (this.ItemTemplate == null)
  {
    return;
  }

  //Create and attach children
  foreach (var item in items)
  {
    var element = this.ItemTemplate.LoadContent() as FrameworkElement;
    element.DataContext = item;
    this.Children.Add(element);
  }

  //Realign in container
  Refresh();
}

How should the custom control look in XAML? EqualDistanceStackPanel gets a collection of items, e.g. of UIElement type.

<Grid xmlns:c="clr-namespace:Avivo.Controls">
  <c:EqualDistanceStackPanel ItemsSource="{Binding Items}" Orientation="Vertical">
    <c:EqualDistanceStackPanel.ItemTemplate>
      <DataTemplate>
        <ContentPresenter Content="{Binding}" />
      </DataTemplate>
    </c:EqualDistanceStackPanel.ItemTemplate>
  </c:EqualDistanceStackPanel>
</Grid>

Example

Ruler has been made to demonstrate the usage of EqualDistanceStackPanel. Numbers are bound to the control and ticks are bound to another control using the same binding collection. Left image represents container height 300px and right when resized to 460px – elements are automatically aligned with equal distance.

Try demo, resize browser to see the effect. This control has been originally developed for custom chart axes in QR Code Statistics application. EqualDistanceStackPanel control is lightweight, works for the statistics application and should be improved for general usage.

Source code

• Source code, Visual Studio sample Silverlight and web project

References

• Using DataTemplates in custom controls

TrimWhiteSpaces accepts raw HTML content and removes white spaces, tabs, new line characters, ‘br’ tags and ‘ ’ chunks from before and after the actual content.

public static string TrimWhiteSpaces(string html)
{
  string result = html;

  //Remove leading spaces
  result = Regex.Replace(result, @"^(?<leading>(\s|\r|\n|\<br\s*/?\>|&nbsp;)*)", "",
RegexOptions.IgnoreCase);

  //Remove trailing spaces
  result = Regex.Replace(result, @"(?<trailing>(\s|\r|\n|\<br\s*/?\>|&nbsp;)*)$", "",
RegexOptions.IgnoreCase);

  return result;
}

&nbsp;<br /><BR   ><BR> &nbsp;
&nbsp;&nbsp;<br />
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>
&nbsp;&nbsp;<br />
<p>Pellentesque lorem neque, accumsan eget euismod ut, tristique et odio.</p>
&nbsp;<br /> <br>
&nbsp;

<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>
&nbsp;&nbsp;<br />
<p>Pellentesque lorem neque, accumsan eget euismod ut, tristique et odio.</p>

1. If you have a UserControl which you add dynamically to your form and if you attach events dynamically to this UserControl using:< br />

   ucMyControl.btnSave.Click += new EventHandler(btnSave_Click);
   

   and if you are removing you UserControl from the form using Controls.Clear() method then you must first remove all attached events before removing your UserControl using

   ucMyControl.btnSave.Click -= new EventHandler(btnSave_Click);
   

2. When removing dynamically added control from Form/Panel calling Controls.Clear() is not enough and instance stays in the heap after thar, so before this command call Dispose() on your dynamically added UserControl (that means that you should save a reference to your control in order to dispose it after)
3. If you have modal forms do not forget to call Dispose() after ShowDialog() method and set their reference to null in order to be garbage collected!

   MyDialog dialog = new MyDialog();
   dialog.ShowModal();
   dialog.Dispose();
   dialog = null;
   

1. Drag a TableLayoutPanel control from the Toolbox onto your form.
2. Drag a ListBox control from the Toolbox into the upper-left cell of the TableLayoutPanel control.
3. Set the ListBox control’s ColumnSpan property to 2. Note that the ListBox control spans the first and second columns.

http://www.yourdomain.com?param1=value1&param2=value2&param3=value3&param4=value4

and you want to get key-value pairs such as

• {“param1″, “param2″, “param3″, “param4″}
• {“value1″, “value2″, “value3″, “value4″}

It is easy to do using system function:

using System.Collections.Specialized;
NameValueCollection query = HttpUtility.ParseQueryString(queryString);
Response.Write(query["param1"]);

It is simple as this (i.e. assuming that your list is named yourItems):

yourItems.RemoveAll(x => x.ItemPropertyId != null);

That means we had to remove thousand separator and needed to force dot as decimal separator (btw, we are SI culture and we use comma as decimal separator and dot is thousand separator).

This is the way how to do it:

CultureInfo ci = CultureInfo.GetCultureInfo("en-US");
NumberFormatInfo nfi = (NumberFormatInfo)ci.NumberFormat.Clone();
//Now force thousand separator to be empty string
nfi.NumberGroupSeparator = "";
//Format decimal number to 2 decimal places
string decimalFormatted = product.Price.ToString("n2", nfi);