Add Google Plus One Extension to BlogEngine.NET

A few years ago I built my personal website using BlogEngine.NET, every once in a while I tend to pay attention to the site and “freshen it up”.  Back in December of 2011, I upgraded to version 2.5 of BlogEngine.NET and updated the theme.  Last night I added facebook like buttons to all those post and pages courtesy of isharpnote. Well I wanted to add a Google Plus One button to my site also but I could not find any BlogEngine.NET extensions for it, so what does every developer do, create one.  I started with the “Facebook Like with Google Plus Extension for BlogEngine 2.5” extension from isharpnote and tweaked it for my needs.

Creating the extension

To create a BlogEngine.NET extension you need a class and attribute it with the BlogEngine.Core.Web.Extensions.Extension attribute, like so:

[Extension(
	"Adds the Google Plus One to your blog Posts", 
	"1.0", 
	"<a href=\"http://www.josephguadagno.net/\">Joseph Guadagno</a>",
	800)]

Parameters explained

This class will need to reside in the App_Code\Extensions folder of your site.

Next step, if you want to have settings, you will need to tell the extension manager that you have settings.  You do this by executing code similar to this, in the constructor of your extension or a method that is called in the constructor of your extension.

var settings = new ExtensionSettings(ExtensionName)
  {Help = "Adds Google Plus One to your Post Home page and Post page", IsScalar = true};

  settings.AddParameter("size", "Size", 20, false, false, ParameterType.ListBox);
  settings.AddValue("size", new[] { "standard", "small", "medium", "tall" }, "standard");
  ExtensionSettings = ExtensionManager.InitSettings(ExtensionName, settings);

In my extension I call a method called InitializeSettings in the constructor

public GooglePlusOne()
{
  InitializeSettings();
  Post.Serving += ServingHandler;
  Page.Serving += ServingHandler;
}

You'll notice that I attached two events, Post.Serving and Page.Serving, to the ServingHandler method. This will tell BlogEngine.NET that I want to know when it is serving up pages or blog posts.

Handling the page and post serving

void ServingHandler(object sender, ServingEventArgs e)
{
  if (!ExtensionManager.ExtensionEnabled(ExtensionName)) return;
  if (e.Location == ServingLocation.Feed) return;

  HttpContext context = HttpContext.Current;
  if (context != null)
  {
    System.Web.UI.Page page = context.CurrentHandler as System.Web.UI.Page;
    if (page != null)
    {
      ScriptInject(page);
    }
  }
  var post = sender as Post;
  if (post != null)
      e.Body += GetButton(post.AbsoluteLink.AbsoluteUri);
}

On line 3 you'll not the check to see if the extension is enabled.  Believe it or not, people might turn off your extension.

Line 4 checks to see if this is in a feed, if so, we do not want to apply the button to the page or post.

Line 6 - 10, I get a reference to the page so that I can inject the required JavaScript for the Google Plus One button.

public static void ScriptInject(System.Web.UI.Page page)
{
  HtmlGenericControl googleScript = new HtmlGenericControl("script");
  googleScript.Attributes["type"] = "text/javascript";
  googleScript.Attributes["src"] = "https://apis.google.com/js/plusone.js";
  page.Header.Controls.Add(googleScript);
}

Next, I get a reference to the post and append to the body of the post the Google Plus One button.

public static string GetButton(string url)
{
  string size = ExtensionSettings.GetSingleValue("size") jQuery152015469422082135964_1326909846817 "standard";
  string googlebutton = string.Format("<g:plusone size=\"{0}\" href=\"{1}\"></g:plusone>", size, url);
  return googlebutton;
}

That's it. You can download the complete extension here GooglePlusOne.cs (2.13 kb)

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DebuggerDisplay Attribute

Have you ever tried to debug an application and wish the Visual Studio debugger did not display {Namespace.ObjectName} when you wanted to see some of the details of the objects?

Visual Studio has an attribute that you can add to a class to inform the debugger what to display when it is displaying that class in the debugger.  As you probably guessed the attribute is called DebuggerDisplay.

How to Implement

Let’s say we have a simple class called Person, the Person class has 4 properties; FirstName, MiddleName, LastName and FullName. Here is the definition:

public class Person

{

  public string FirstName { get; set; }
  public string MiddleName { get; set; }
  public string LastName { get; set; }    
  public string FullName
  {
    get
    {
      return string.Format("{0} {1}{2}", FirstName,
        (string.IsNullOrEmpty(MiddleName)) ? string.Empty : MiddleName + "", 
        LastName);
    }
  }
}

Next, let’s assume we want to display the first and last name of the person when debugging.  We first need to add the DebuggerDisplay attribute to our class.  The DebuggerDisplay attribute can be found in the System.Diagnosis class of the .NET framework. The DebuggerDisplay works almost like the string.Format method, except you replace the numbers with the property / method names you want to display.

Example:

[DebuggerDisplay("FirstName={FirstName} LastName={LastName}")]

This will tell the debugger to display the string FirstName= with the value of the FirstName field in double quotes followed by LastName= with the value of the LastName field in double quotes every time it needs to display a person object.  Here is our new class:

[DebuggerDisplay("FirstName={FirstName} LastName={LastName}")]
public class Person
{
  public string FirstName { get; set; }
  public string MiddleName { get; set; }
  public string LastName { get; set; }    
  public string FullName
  {
    get
    {
      return string.Format("{0} {1}{2}", FirstName,
          (string.IsNullOrEmpty(MiddleName)) ? string.Empty : MiddleName + "", 
          LastName);
    }
  }
}

This will display like so:

You’ll notice this makes it easier to see what you are looking at.  It also works in the immediate window.

Summary

You can use more than just field names.  Method calls can be done (although probably not the best) and some calculations.  Take a look at the MSDN documentation for the DebuggerDisplay attribute for more information.

There is also an article titled DebuggerDisplay attribute best practices that you should read also.

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