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Multiple select listbox in MVC 4

This post will be in Dutch because I based this on a discussion with someone else.

Vandaag gaf ik al weer voor de vierde keer les op de Hogeschool van Rotterdam. Daar geef ik les aan een groep studenten in het vak Microsoft ASP .NET MVC 4 met alle standaard tools als Entity Framework en Web API er om heen.

Bob Joziasse sprak ik vandaag over een multiple select in een listbox voor zijn laatste blog Eggplication die in het leuke paas thema is geschreven. Ik ben er even ingedoken aangezien ik zelf de listbox in HTML nooit gebruik. Op zich is het een standaard control en het is al snel duidelijk voor een gebruiker wat hij er mee kan doen. Ik zelf gebruik hem nooit omdat de styling van het control niet voor elke browser gelijk is. Maarja, terug naar het onderwerp.

In zijn blog heeft Bob een kleine applicatie gemaakt om aan het te geven hoe een meer op meer relatie werkt door middel van Code First in het wel bekende Entity Framework. In de applicatie kan je een ei maken en die verschillende templates geven voor het beschilderen. Ik heb de applicatie hetzelfde genoemd maar de properties van de objecten een beetje mijn eigen gang laten gaan. Zo heb ik ook een meer op meer relatie en kan ik dus templates koppelen aan een ei en eieren koppelen aan (schilder)templates.

De objecten zien er als volgt uit:

Egg:

Template:

Simpele ViewModel voor de Create van de Egg:

De database wordt dan als volgt gegenereerd:

De controller met de Create Get en Post functies zien er dan als volgt uit:

Om dit werkend te krijgen hebben we natuurlijk ook een View nodig. Dit ziet er bij mij zo uit:

Als we dit draaien ziet dat er als volt uit:

Om vervolgens dit weer te kunnen bekijken heb ik het als volgt gemaakt:

Wat resulteert in onderstaande om het ei met de gekozen templates te kunnen weergeven:

Een simpele applicatie maar wel handig om snel een meer op meer relatie te maken met een listbox.

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Localization validation in MVC

Last week I was working on a bug for my website SeeTings. The bug was the validation of a DateTime not working in Firefox and Chrome. In Internet Explorer (even version 9) was working correct.

After hours searching and hundreds of form posts further, I finally found the solution. I thought the problem was in implementing the jQuery UI Date picker with the Dutch Format of a date (dd-MM-yyyy) in it but that wasn’t true.

The problem was the client validation of the jQuery Validation plugin. ASP .NET MVC 3 and 4 are shipped with an installed version of jQuery. And the internet template (the one that I was using) creates a login and register process.

To test the bug, I created a new project and added a DateTime field called Birthday to the register login form. I deleted all other fields except the UserName field because then I could test if the Required validation still worked if I might fined a solution for the validation problem.

After long searching, I saw this post http://stackoverflow.com/a/511670 on Stackoverflow. There was another script file called “additional-methods.js” that I didn’t heard of. After long searching, I found the official website of jQuery validation http://bassistance.de/jquery-plugins/jquery-plugin-validation/ and saw the CDN of all the jQuery instances.

It seemed not necessary to link the additional-methods.js file because that would only add extra validation like credit card or url TLD and email TLD etc. checking.  I found out that jQuery validation had multiple localization files. One for the messages and one for one other thing and that was my problem, the date validation.

When you go to the CDN of Microsoft, you will see in version 1.6 (current version is 1.9) a long list of localization files.

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The files ending with messages_xxx.js are the error messages localized. The files ending with methods_xx.js (like for me methods_nl.js) are the localized versions of some script. In this case only the date.

So reference on your page where you need to do the validation, the standard validation scripts of jQuery and after that you need to reference you localization file. Only do this if the browser is that language. So I only reference the script file if I know that the browser is Dutch. You can find the current language settings of the browser with JavaScript as well. You can change the url of the CDN from 1.6 to 1.9 and it will still work. Why the files are not listed on the 1.9 page, I don’t know.

After completing this above, you can after that implementing the jQuery Datepicker. Don’t forget that the Datepicker of jQuery UI also needs a localization reference file. See the last part of the documentation on this page http://jqueryui.com/demos/datepicker/. Just reference the file and everything is working.

Good luck and hopefully you guys aren’t that long busy figuring out why the validation isn’t working.

OutputCache explanation

Why should we use caching?

The reason why we should use caching is to increase the performance for the end user and to decrease the traffic on the server. There are multiple kind of caching. In this post, I will explain the OutputCache attribute of MVC 3 (and 4).

Using the OutputCache Attribute

To cache a page or image in ASP .NET MVC 3 we only have to set the OutputCache attribute above the action.

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The Duration property is the timespan you want to cache the action in seconds. So above, the page will be cached for 10 seconds. When you run the application, the page is showing the ViewBag.Time on your screen. If you hit F5 (refresh), the page is refreshed but your action isn’t. The time is still the same if you did refresh the page within the 10 seconds. When you hit F5 after 10 seconds, the new time is shown.

Use fiddler to see if the caching is working.

Caching the action for different result

When you have an action for different results, like asking for an image for a given imageId you use a parameter in your action. The OutputCache attribute will automatically use the parameter for caching the result for that specific item.

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So when you ask for example image 3 and 24, the caching will work on both images.

Use fiddler to see if the caching is working.

Caching of private items

By default, the cache is saved on the server and client. But when you have private data the cache should only be used on the client (the browser). Otherwise, private data could be accessed by anyone.

We could use the location property for this.

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Set the location property to Client to only store the image in the browser.

When you run the page now and see the image or page, the image or page is cached only in your browser. When you hit F5, the caching won’t work. This is because client caching will not work for browser refreshing. If you use a hyperlink to the same page or image the caching will work.

Again use fiddler to see the results.

How to disable caching of an action

To disable caching for an action, use the code as shown below.

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Caching profiles

When you have a lot of actions with the same settings, you could implement caching profiles. In this way, you only have to change the settings on one place.

In the web.config, add the following section.

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You then could use the caching profile in the following way.

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Minification and Bundling in MVC 4 RC

Asp .NET MVC 4 Release Candidate is out. One of the features that is included is called the minification and bundling feature. This was already there in the beta but in the release candidate version it has changed.

Why should we use it

The reason why we should use the bundling and minification feature is performance. The features increases your loading performance of your website. Every time you reference a JavaScript (like jQuery or your own), or CSS file in your page, the browser makes a call to the server. This is done for each separate reference. Each referenced file has included all the comments and spacing in your file. This makes the file larger then when we should delete those spaced. The bundling and minification feature does this for us.

How does it work

In your Global.asax the CSS and JavaScript files are Bundled with BundleConfig.RegisterBundles(BundleTable.Bundles); line.

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Reference the files in your page.

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When you run the application and use Fiddler to view the calls to your server, you still see all the files called separately.

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This is because the Bundling and Minification feature by default only work when your not in debug mode. This handy because then you could debug with all the whitespaces in your files and have the performance in the production environment.

See the difference in your production environment:

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Force Bundling and Minification

You can use the BundleTable.EnableOptmizations override but the best way for a little test is to remove the debug=”true” attribute in your web.config.

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Browser caching

When the feature is active, the browser will cache the files. When you add or change some JavaScript or CSS code, the files are generated again and the version number in the references are updated. In that way, the browser knows that there is a new version and your website wont brake.

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ASP .NET MVC 3 Release Candidate released

Ralph JansenOn November 9th 2010 the ASP .NET team released the release candidate of MVC 3. The big change of MVC 3 is the new “Razor” view engine. With this new view engine the syntax of the code is a lot smaller. You now just put an @ on your editor and the intellisense will pick it up.

An other thing that is added in MVC 3 is: partial caching of pages. You can add an attribute above your action in the controller with the right amount of seconds that you want to cache the information. You can even say what the dependent parameter is that the caching will focus on. So if an action is fired and the parametervalue is the same as a previous parametervalue within the specified amount of time, the data will come out of the cache. That way, no database call is required!!!

Check for more information the blog of Scott Guthrie or the official ASP .NET MVC 3 Releas Candidate page.