One of the really cool aspects of Depency Injection is the ability to add functionality without changing existing code. A typical example of this might be implementing INotifyPropertyChanged or logging method calls. Using NInject 3.0 Interceptors it is very easy to do this. The interceptor intercepts all calls to the resolved object and allows you to add logging or whatever code you want to run. In NInject 3.0 the methods you intercept do NOT have to be virtual as well :) So how to set it up...

Getting the right assemblies.

Using Nuget just get NInject.Extensions.Interception.Linfu. This will also setup NInject 3.0 and NInject.Extensions.Interception.

Creating the logging Interceptor

This is just a sample interceptor that logs using Console.Writeline. Normally you would call something like Log4Net or your preferred logging framework. Implementing IInterceptor means you have to implement a Intercept method. The Intercept method gets a invocation as a parameter. By invocation.Proceed() the original method gets called. The logger first logs the method being called and the arguments it is called with. After the invocation.Proceed() it logs the result of the method call. The interceptor is pretty simple and can certainly be improved by creating nicer more custom messages.

public class LoggingInterceptor : IInterceptor

    {

        public void Intercept(IInvocation invocation)

        {

            var methodName = invocation.Request.Method.Name;

            try

            {

                var parameterNames = invocation.Request.Method.GetParameters().Select(p => p.Name).ToList();

                var parameterValues = invocation.Request.Arguments;

                var message = string.Format("Method {0} called with parameters ", methodName);

                for (int index = 0; index < parameterNames.Count; index++)

                {

                    var name = parameterNames[index];

                    var value = parameterValues[index];

                    message += string.Format("<{0}>:<{1}>,", name, value);

                }

                //log method called

                LogMessage(message);

                //run the intercepted method

                invocation.Proceed();

                //log method return value

                if (invocation.Request.Method.ReturnType != typeof(void))

                {

                    LogMessage(string.Format("Method {0} returned <{1}>", methodName, invocation.ReturnValue));

                }

            }

            catch (Exception ex)

            {

                var message = string.Format("Method {0} EXCEPTION occured: {1} ", methodName, ex);

                LogMessage(message);

                throw;

            }

        }

        private static void LogMessage(string message)

        {

            Console.WriteLine(string.Format("{0:HH:mm} {1}", DateTime.Now, message));

        }

    }

Adding the logging interceptor to your NInject Configuration

In your kernel configuration you can add interceptors to your bindings like this :

kernel.Bind<IService>().To<Service>().Intercept().With<LoggingInterceptor>();

Now when getting a IService using Kernel.Get<IService> the logginginterceptor will be interception all method calls :) A working sample console application can be found here: 

SampleLogging.rar (2.86 mb)

SampleLogging.rar (2.86 mb)

Should I use base64?

In this era of optimization and mobilization having a lot of request to load your website is considered a bad thing. One of the things you can do is 'inline' your images in your CSS file using a base64 format. This way the browser can get the CSS and the images in one big request.

There are some cons to this :

• Images are not cached separately and when you change your css the download will be bigger.
• IE6 and IE7 don't support base64 images in CSS. You can use a fallback tag for these browsers.
• Your development gets more complex as you have to remember to update the base64 images in your css when you modify an image.
• Images in css are about 37% larger than in a separate file.
• Works for images up to 37k in IE8
• Stylesheets get really large 

Also you might consider using a spritesheet which can be cached seperately (like jQuery UI does for example) or create a separate stylesheet for your inlined-images so your cache will not be invalidated when you change something else in you stylesheet. Some more considerations and opinions at Stackoverflow....

Creating a bundle transform to inline the images

So still interested? Some of the development disadvantages can be avoided by using a bundle transform. A bundle transform is part of the System.Web.Optimization library by Microsoft. The basic idea of bundling is combining multiple css or jss files into one big file at runtime. You can configure System.Web.Optimization to only optimize when you are in release mode so that during development you have separate readably resources. This post is about creating a bundle that replaces background-image:url('/yourimage') which base64 urls during optimization.

As you can see the image is inlined (in the 28796 characters) and a fallback for IE6/IE7 is supplied as well. 

This can be done at development time easily with the web essentials extension by Mads Kristensen. The idea of this transform is to perform the operation at runtime. The main advantage is that your development is not cluttered with having to regenerate images and having optimization only on production code.

Here's the code

So let's get into the details. Sorry for the missing syntax highlighting. I have not fixed that yet.

[code:c#]

 public class CssBaseEncodeTransform : IBundleTransform

    {

        public void Process(BundleContext context, BundleResponse response)

        {

            response.Content = InlineBase64BackgroundImages(response.Content, BundleTable.MapPathMethod);

        }

        public static string InlineBase64BackgroundImages(string content, Func<string, string> mappath)

        {

            //find background-images

            var parser = new CSSParser();

            var cssDocument = parser.ParseText(content);

            foreach (RuleSet rule in cssDocument.RuleSets)

            {

                var declarations = rule.Declarations.ToList();

                foreach (var declaration in declarations)

                {

                    if (declaration.Name == "background-image")

                    {

                        rule.Declarations.Add(GetIe6Declaration(declaration));

                        EmbedUrlInBackground(declaration,mappath);

                    }

                }

            }

            return cssDocument.ToString();

        }

        private static Declaration GetIe6Declaration(Declaration declaration)

        {

            var copy = new Declaration();

            copy.Expression = new Expression()

                {

                    Terms = new List<Term>{new Term() {Value = declaration.Expression.Terms.First().Value}}

                };

            copy.Name = "*background-image";

            return copy;

        }

        private static void EmbedUrlInBackground(Declaration declaration, Func<string, string> mappath)

        {

            var imageUrl = declaration.Expression.Terms[0].Value;

            var image = Image.FromFile(Path.GetFullPath(mappath(imageUrl)));

            var data = ImageToBase64(image, ImageFormat.Jpeg);

            var url = string.Format(@"data:image/jpg;base64,{0}", data);

            declaration.Expression.Terms[0].Value = url;

        }

        public static string ImageToBase64(Image image,ImageFormat format)

        {

            using (MemoryStream ms = new MemoryStream())

            {

                // Convert Image to byte[]

                image.Save(ms, format);

                byte[] imageBytes = ms.ToArray();

                // Convert byte[] to Base64 String

                string base64String = Convert.ToBase64String(imageBytes);

                return base64String;

            }

        }

    }

[code]

1. The code basically looks for background-image declarations in your style sheet.
2. If found replace the url('/image') with the base64 equivalent.
3. A *background-image declaration is added for IE6/7 support.

Usage

Just add the transform to the bundle :

The code use the simple css parser project which can be found here (and is included in the zip). The source code is also included at the bottom. Hope is this of some use or inspiration!

Base64Bundling.zip (997.47 kb)

In this post I want to talk about a little tool called Weld I wrote to make integrating client-side TypeScript and server side MVC C# easy. 

Imagine you have a server-side method that calculates some value you want to use client side. In this sample project I want to calculate the sum of two values I have in input fields.

Server-side I have this action-method in my home controller.

public int Sum(int x,int y)
{
return x + y;
}

Now to access this method client I just need to add a Weld attribute. For this I first install Weld using NuGet. 
Just “Install-Package Weld” in your NuGet package manager console. This will install Weld as well a TypeScript.Compile and JQuery typings into your project. 

TypeScript.Compile auto compiles all your typescript files post-build. This enables you to detect any problems caused by server side changes. 

The basic process :

1. Normal compilation
2. Weld generates TypeScript code for the classes your decorated with Weld attributes
3. TypeScript compiles all files in your project with build actions 'TypeScriptCompile'

For this sample I add the AjaxMethod (Weld.Attributes.AjaxMethod) attribute to the ‘Sum’ action. 

Compile the project. Weld now has generated a proxy class for my home controller. I just need to include it and used it in the project. It is located in the /Scripts/Weld folder. 

I add the generated homecontroller.ts to my project. I my main TypeScript file I write the following to hook it all up:

/// <reference path="Weld/HomeController.ts" />/// <reference path="typings/jquery/jquery.d.ts" />
$(document).ready(function () {
$("#btnSum").click(function () {
HomeController.prototype.Sum($("#number1").val(), $("#number2").val(), (result) => {
$("#result").text(result);
});
});    
});

As you can see the details of the Ajax communication are handled by weld and you get a nice interface to your server side API :)

When editing boolean values in MVC the default option is to use a checkbox. This results in the following Create page when using the default scaffolding

This is fine and works OK but sometimes you want something more..’fancy’. ASP.NET MVC ships with Jquery.UI so why no use the slider of JQuery.UI to create a nice toggle switch?

In this post I will use and modify a JQuery.UI plugin that will result in the following. The plugin is based on http://taitems.github.io/UX-Lab/ToggleSwitch/ which had some errors in my opinion.

There are a two parts to this:

1. Create a HTMLHelper extension method that renders a <select> element for the boolean property with <option> elements for true and false
2. Change the rendered <select> element to a jquery slider using a JQuery.UI plugin

Creating the HTMLHelper

public static class HtmlHelperExtensions
{
public static MvcHtmlString ToggleSwitchFor<TModel>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, bool>> expression)
{
return htmlHelper.DropDownListFor(expression, new[]
{
new SelectListItem { Text = "No", Value = "false" },
new SelectListItem { Text = "Yes", Value = "true" } 
}, new { @class = "toggleswitch" });
}
}

This adds a HTMLHelper method that renders a dropdown list which comes down to a single select HTML element. There are two options in the select : one for true and one for false. To use it we just do 

@Html.ToggleSwitchFor(model => model.CommentsEnabled)

And we get the following html

<select class="toggleswitch" data-val="true" data-val-required="The CommentsEnabled field is required." id="CommentsEnabled" name="CommentsEnabled"><option value="false">No</option><option value="true">Yes</option></select>

This is all what we need to get our JQuery plugin going.

Creating the JQuery plugin

The plugin uses the JQuery.UI slider to create a toggle switch. This means that any styling or theme you might have for the slider will work for the toggle as well. The plugin transforms the select element into two labels with a slider in between. When you click on a label or move the slider the select control will be updated as well and when you do form post the values get updated. The http://taitems.github.io/UX-Lab/ToggleSwitch/ had two errors when I tried it

1. The change event was just passing the change event of the slider. This meant even if the boolean property did not change (you moved the slider a little) you would still get a change event. In this version the change event is only fired when the value really changed.
2. The plugin did not allow chaining.
3. The normal ‘change’ event of JQuery was no longer fired. This is fixed by not having a change event on the control itself but just fire the existing change event.

To use it you need to add the CSS and JS of the plugin to your page. You also need the default JQuery UI js and css (which is not referenced by default!). Once you have done that you can activate the plugin for a control:

$(document).ready(function () {
$("#CommentsEnabled").toggleSwitch().change(function() {
alert("Changed!!");
});
});

I attached a sample MVC application as well as the JQuery.UI.ToggleSwitch plugin.

$project = Get-Project
$buildProject = Get-MSBuildProject
$target = $buildProject.Xml.AddTarget("WeldAfterbuild")
$target.AfterTargets = "AfterBuild"
$task = $target.AddTask("Exec")
$task.SetParameter("Command", "`".\..\packages\Weld.1.0.0\tools\Weld.console`" bin\`$(TargetFileName) `"`$(ProjectDir)\Scripts\Weld`"")
$project.Save() #persists the changes

<Target Name="WeldAfterbuild" AfterTargets="AfterBuild">
<Exec Command="&quot;.\..\packages\Weld.1.0.0\tools\Weld.console&quot; bin\$(TargetFileName) &quot;$(ProjectDir)\Scripts\Weld&quot;" />
</Target>

Removing a build target from a project

$project = Get-Project
$buildProject = Get-MSBuildProject
$projectRoot = $buildProject.Xml;
Foreach ($target in $projectRoot.Targets)
{
If ($target.Name -eq "WeldAfterbuild")
{
$projectRoot.RemoveChild($target);
}
}
$project.Save() #persists the changes

Intro

Offcourse you need a XSD to define the structure of your xml but once you have that the API is much nicer than the general LinqToXML.

Setting it up in Visual Studio

What does this do?