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  • Class-Level Model Validation with EF Code First and ASP.NET MVC 3

    - by ScottGu
    Earlier this week the data team released the CTP5 build of the new Entity Framework Code-First library.  In my blog post a few days ago I talked about a few of the improvements introduced with the new CTP5 build.  Automatic support for enforcing DataAnnotation validation attributes on models was one of the improvements I discussed.  It provides a pretty easy way to enable property-level validation logic within your model layer. You can apply validation attributes like [Required], [Range], and [RegularExpression] – all of which are built-into .NET 4 – to your model classes in order to enforce that the model properties are valid before they are persisted to a database.  You can also create your own custom validation attributes (like this cool [CreditCard] validator) and have them be automatically enforced by EF Code First as well.  This provides a really easy way to validate property values on your models.  I showed some code samples of this in action in my previous post. Class-Level Model Validation using IValidatableObject DataAnnotation attributes provides an easy way to validate individual property values on your model classes.  Several people have asked - “Does EF Code First also support a way to implement class-level validation methods on model objects, for validation rules than need to span multiple property values?”  It does – and one easy way you can enable this is by implementing the IValidatableObject interface on your model classes. IValidatableObject.Validate() Method Below is an example of using the IValidatableObject interface (which is built-into .NET 4 within the System.ComponentModel.DataAnnotations namespace) to implement two custom validation rules on a Product model class.  The two rules ensure that: New units can’t be ordered if the Product is in a discontinued state New units can’t be ordered if there are already more than 100 units in stock We will enforce these business rules by implementing the IValidatableObject interface on our Product class, and by implementing its Validate() method like so: The IValidatableObject.Validate() method can apply validation rules that span across multiple properties, and can yield back multiple validation errors. Each ValidationResult returned can supply both an error message as well as an optional list of property names that caused the violation (which is useful when displaying error messages within UI). Automatic Validation Enforcement EF Code-First (starting with CTP5) now automatically invokes the Validate() method when a model object that implements the IValidatableObject interface is saved.  You do not need to write any code to cause this to happen – this support is now enabled by default. This new support means that the below code – which violates one of our above business rules – will automatically throw an exception (and abort the transaction) when we call the “SaveChanges()” method on our Northwind DbContext: In addition to reactively handling validation exceptions, EF Code First also allows you to proactively check for validation errors.  Starting with CTP5, you can call the “GetValidationErrors()” method on the DbContext base class to retrieve a list of validation errors within the model objects you are working with.  GetValidationErrors() will return a list of all validation errors – regardless of whether they are generated via DataAnnotation attributes or by an IValidatableObject.Validate() implementation.  Below is an example of proactively using the GetValidationErrors() method to check (and handle) errors before trying to call SaveChanges(): ASP.NET MVC 3 and IValidatableObject ASP.NET MVC 2 included support for automatically honoring and enforcing DataAnnotation attributes on model objects that are used with ASP.NET MVC’s model binding infrastructure.  ASP.NET MVC 3 goes further and also honors the IValidatableObject interface.  This combined support for model validation makes it easy to display appropriate error messages within forms when validation errors occur.  To see this in action, let’s consider a simple Create form that allows users to create a new Product: We can implement the above Create functionality using a ProductsController class that has two “Create” action methods like below: The first Create() method implements a version of the /Products/Create URL that handles HTTP-GET requests - and displays the HTML form to fill-out.  The second Create() method implements a version of the /Products/Create URL that handles HTTP-POST requests - and which takes the posted form data, ensures that is is valid, and if it is valid saves it in the database.  If there are validation issues it redisplays the form with the posted values.  The razor view template of our “Create” view (which renders the form) looks like below: One of the nice things about the above Controller + View implementation is that we did not write any validation logic within it.  The validation logic and business rules are instead implemented entirely within our model layer, and the ProductsController simply checks whether it is valid (by calling the ModelState.IsValid helper method) to determine whether to try and save the changes or redisplay the form with errors. The Html.ValidationMessageFor() helper method calls within our view simply display the error messages our Product model’s DataAnnotations and IValidatableObject.Validate() method returned.  We can see the above scenario in action by filling out invalid data within the form and attempting to submit it: Notice above how when we hit the “Create” button we got an error message.  This was because we ticked the “Discontinued” checkbox while also entering a value for the UnitsOnOrder (and so violated one of our business rules).  You might ask – how did ASP.NET MVC know to highlight and display the error message next to the UnitsOnOrder textbox?  It did this because ASP.NET MVC 3 now honors the IValidatableObject interface when performing model binding, and will retrieve the error messages from validation failures with it. The business rule within our Product model class indicated that the “UnitsOnOrder” property should be highlighted when the business rule we hit was violated: Our Html.ValidationMessageFor() helper method knew to display the business rule error message (next to the UnitsOnOrder edit box) because of the above property name hint we supplied: Keeping things DRY ASP.NET MVC and EF Code First enables you to keep your validation and business rules in one place (within your model layer), and avoid having it creep into your Controllers and Views.  Keeping the validation logic in the model layer helps ensure that you do not duplicate validation/business logic as you add more Controllers and Views to your application.  It allows you to quickly change your business rules/validation logic in one single place (within your model layer) – and have all controllers/views across your application immediately reflect it.  This help keep your application code clean and easily maintainable, and makes it much easier to evolve and update your application in the future. Summary EF Code First (starting with CTP5) now has built-in support for both DataAnnotations and the IValidatableObject interface.  This allows you to easily add validation and business rules to your models, and have EF automatically ensure that they are enforced anytime someone tries to persist changes of them to a database.  ASP.NET MVC 3 also now supports both DataAnnotations and IValidatableObject as well, which makes it even easier to use them with your EF Code First model layer – and then have the controllers/views within your web layer automatically honor and support them as well.  This makes it easy to build clean and highly maintainable applications. You don’t have to use DataAnnotations or IValidatableObject to perform your validation/business logic.  You can always roll your own custom validation architecture and/or use other more advanced validation frameworks/patterns if you want.  But for a lot of applications this built-in support will probably be sufficient – and provide a highly productive way to build solutions. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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  • A conversation with Paul Rademacher and Mano Marks, Google Maps API Office Hours

    A conversation with Paul Rademacher and Mano Marks, Google Maps API Office Hours This is a conversation between Paul Rademacher and Mano Marks on April 24th, 2012. Paul created the first Google Maps Mashup, housingmaps.com, and discusses his latest project, Stratocam, which allows users to find and display beautiful satellite and aerial imagery with the Google Maps API. From: GoogleDevelopers Views: 1199 11 ratings Time: 40:08 More in Science & Technology

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  • Master database Compatibility level after an In-place Upgrade

    - by Jonathan Kehayias
    Yesterday a forums member asked why sys.dm_exec_sql_text() wouldn’t work on one instance of SQL where he was a sysadmin while the same code worked correctly on another instance of SQL.  The initial thought was that it was some kind of permissions issue.  Ken Simmons ( blog / twitter ) pointed out that the compatibility level of the database would affect the ability to use this DMF and that running it from a database at 80 compatibility would fail.  It turns out the person was running...(read more)

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  • OAuth 2.0 for Google Drive and the Adsense API

    OAuth 2.0 for Google Drive and the Adsense API Google engineers Nicolas Garnier, Ali Afshar, and Sergio Gomes discuss the OAuth 2.0 playground and how to use it with the Google Drive And AdSense APIs. OAuth 2.0 and its inner workings are explained in detail, and usage of the OAuth 2.0 playground in context of Google Drive and the AdSense API is demonstrated thoroughly. The sessions wraps up with some discussion of questions from live viewers. From: GoogleDevelopers Views: 9 0 ratings Time: 57:02 More in Science & Technology

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  • Thinktecture.IdentityModel.Http and the ASP.NET Web API CodePlex bits

    - by Your DisplayName here!
    I will keep the github repo in sync with the major releases of Web API (like Beta, RC, RTM). Because of the changes made to Web API after beta, my current bits don’t build against the CodePlex version anymore. Today I installed a build environment for the CodePlex bits, and migrated my code. It turns out the changes are pretty easy: Simply replace Request.GetUserPrincipal() with Thread.CurrentPrincipal ;) I will update the repo when RC comes out.

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  • How to set the PHP Api Version for phpize

    - by Tom Frost
    I'm upgrading php on my server but I'm running into a problem with phpize and compiling external modules. phpize -v reports: Configuring for: PHP Api Version: 20041225 Zend Module Api No: 20090115 Zend Extension Api No: 220090115 But on my test server (which I'm trying to replicate) I get this: Configuring for: PHP Api Version: 20090626 Zend Module Api No: 20090626 Zend Extension Api No: 220090626 I'm running debian squeeze, pulling the php 5.3.0-2 packages from the experimental repo. The difference betweent he two servers is that the first server has had old verisons of php on it, and the test server was installed with php 5.3.0-2 from the start. I've attempted uninstalling all PHP packages from the first server (using --purge to get rid of all the config files) and re-installing 5.3 fresh, but I'm still having the same issue. Help!

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  • Google Wave Robots API v2

    Google Wave Robots API v2 Pamela Fox describes how Wave Robots works, and new features in Robots API v2. From: GoogleDevelopers Views: 2 0 ratings Time: 17:28 More in Science & Technology

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  • Easy way to set up global API hooks

    Discover an easy way to set up system-wide global API hooks using AppInit_DLLs registry key for DLL injection and Mhook library for API hooking. To illustrate this technique we will show how to easily hide calc.exe from the list of running processes.

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  • Publier des animations Flash avec l'API Java Flagstone Transform SWF, par Mohamed Slim

    bonjour. je viens de terminer mon premier article intitulé JAVA et SWF Cet article est destiné aux développeurs Java qui souhaitent publier des animations Flash, sans utiliser le logiciel Adobe Flash mais en utilisant le langage de programmation Java et l'API Flagstone Transform SWF. Cet article peut être considéré comme une documentation en français pour l'API Flagstone Transform SWF. donc merci de lire l'article et n'hésitez pas à dire ce que vous en pensez. merci ...

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  • Stairway to PowerPivot and DAX - Level 2: The DAX COUNTROWS() and FILTER() Functions

    Bill Pearson, business intelligence architect and author, exposes the DAX COUNTROWS() and FILTER() functions, while generally exploring, comparing and contrasting the nature and operation of calculated columns and calculated measures, in the second Level of our Stairway to PowerPivot and DAX series. 12 essential tools for database professionalsThe SQL Developer Bundle contains 12 tools designed with the SQL Server developer and DBA in mind. Try it now.

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  • Stairway to PowerPivot and DAX - Level 3: The DAX DISTINCT() Function and Basic Distinct Counts

    Bill Pearson, Business Intelligence architect and author, exposes the DAX DISTINCT() function, and then provides some hands-on exposure to its use in generating distinct counts. Moreover, he further explores working with measures in the PivotTable in this, the third Level of our new Stairway to PowerPivot and DAX series. Optimize SQL Server performance“With SQL Monitor, we can be proactive in our optimization process, instead of waiting until a customer reports a problem,” John Trumbul, Sr. Software Engineer. Optimize your servers with a free trial.

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  • Image CDN with API?

    - by Dan Gayle
    My company uses flickr and picasa web albums as poor man's content delivery networks (CDN) for image hosting, but I'm curious if anyone has any recommendations on any other services that might be worth looking into, paid and free? Preferably something that has an API so that it can be integrated discreetly on the backend as a WordPress plugin or for other development frameworks. A CDN such as Amazon is cheap, and it works, but the lack of a photo-centric API is what prevents me from using it for general usage.

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  • Reuse Business Logic between Web and API

    - by fesja
    We have a website and two mobile apps that connect through an API. All the platforms do the exactly same things. Right now the structure is the following: Website. It manages models, controllers, views for the website. It also executes all background tasks. So if a user create a place, everything is executed in this code. API. It manages models, controllers and return a JSON. If a user creates a place on the mobile app, the place is created here. After, we add a background task to update other fields. This background task is executed by the Website. We are redoing everything, so it's time to improve the approach. Which is the best way to reuse the business logic so I only need to code the insert/edit/delete of the place & other actions related in just one place? Is a service oriented approach a good idea? For example: Service. It has the models and gets, adds, updates and deletes info from the DB. Website. It send the info to the service, and it renders HTML. API. It sends info to the service, and it returns JSON. Some problems I have found: More initial work? Not sure.. It can work slower. Any experience? The benefits: We only have the business logic in one place, both for web and api. It's easier to scale. We can put each piece on different servers. Other solutions Duplicate the code and be careful not to forget anything (do tests!) DUplicate some code but execute background tasks that updates the related fields and executes other things (emails, indexing...) A "small" detail is we are 1.3 person in backend, for now ;)

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  • Stairway to XML: Level 1 - Introduction to XML

    In this level, Rob Sheldon explains what XML is, and describes the components of an XML document, Elements and Attributes. He explains the basics of tags, entity references, enclosed text, comments and declarations Schedule Azure backupsRed Gate’s Cloud Services makes it simple to create and schedule backups of your SQL Azure databases to Azure blob storage or Amazon S3. Try it for free today.

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