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  • Calculated Columns in Entity Framework Code First Migrations

    - by David Paquette
    I had a couple people ask me about calculated properties / columns in Entity Framework this week.  The question was, is there a way to specify a property in my C# class that is the result of some calculation involving 2 properties of the same class.  For example, in my database, I store a FirstName and a LastName column and I would like a FullName property that is computed from the FirstName and LastName columns.  My initial answer was: 1: public string FullName 2: { 3: get { return string.Format("{0} {1}", FirstName, LastName); } 4: } Of course, this works fine, but this does not give us the ability to write queries using the FullName property.  For example, this query: 1: var users = context.Users.Where(u => u.FullName.Contains("anan")); Would result in the following NotSupportedException: The specified type member 'FullName' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported. It turns out there is a way to support this type of behavior with Entity Framework Code First Migrations by making use of Computed Columns in SQL Server.  While there is no native support for computed columns in Code First Migrations, we can manually configure our migration to use computed columns. Let’s start by defining our C# classes and DbContext: 1: public class UserProfile 2: { 3: public int Id { get; set; } 4: 5: public string FirstName { get; set; } 6: public string LastName { get; set; } 7: 8: [DatabaseGenerated(DatabaseGeneratedOption.Computed)] 9: public string FullName { get; private set; } 10: } 11: 12: public class UserContext : DbContext 13: { 14: public DbSet<UserProfile> Users { get; set; } 15: } The DatabaseGenerated attribute is needed on our FullName property.  This is a hint to let Entity Framework Code First know that the database will be computing this property for us. Next, we need to run 2 commands in the Package Manager Console.  First, run Enable-Migrations to enable Code First Migrations for the UserContext.  Next, run Add-Migration Initial to create an initial migration.  This will create a migration that creates the UserProfile table with 3 columns: FirstName, LastName, and FullName.  This is where we need to make a small change.  Instead of allowing Code First Migrations to create the FullName property, we will manually add that column as a computed column. 1: public partial class Initial : DbMigration 2: { 3: public override void Up() 4: { 5: CreateTable( 6: "dbo.UserProfiles", 7: c => new 8: { 9: Id = c.Int(nullable: false, identity: true), 10: FirstName = c.String(), 11: LastName = c.String(), 12: //FullName = c.String(), 13: }) 14: .PrimaryKey(t => t.Id); 15: Sql("ALTER TABLE dbo.UserProfiles ADD FullName AS FirstName + ' ' + LastName"); 16: } 17: 18: 19: public override void Down() 20: { 21: DropTable("dbo.UserProfiles"); 22: } 23: } Finally, run the Update-Database command.  Now we can query for Users using the FullName property and that query will be executed on the database server.  However, we encounter another potential problem. Since the FullName property is calculated by the database, it will get out of sync on the object side as soon as we make a change to the FirstName or LastName property.  Luckily, we can have the best of both worlds here by also adding the calculation back to the getter on the FullName property: 1: [DatabaseGenerated(DatabaseGeneratedOption.Computed)] 2: public string FullName 3: { 4: get { return FirstName + " " + LastName; } 5: private set 6: { 7: //Just need this here to trick EF 8: } 9: } Now we can both query for Users using the FullName property and we also won’t need to worry about the FullName property being out of sync with the FirstName and LastName properties.  When we run this code: 1: using(UserContext context = new UserContext()) 2: { 3: UserProfile userProfile = new UserProfile {FirstName = "Chanandler", LastName = "Bong"}; 4: 5: Console.WriteLine("Before saving: " + userProfile.FullName); 6: 7: context.Users.Add(userProfile); 8: context.SaveChanges(); 9:  10: Console.WriteLine("After saving: " + userProfile.FullName); 11:  12: UserProfile chanandler = context.Users.First(u => u.FullName == "Chanandler Bong"); 13: Console.WriteLine("After reading: " + chanandler.FullName); 14:  15: chanandler.FirstName = "Chandler"; 16: chanandler.LastName = "Bing"; 17:  18: Console.WriteLine("After changing: " + chanandler.FullName); 19:  20: } We get this output: It took a bit of work, but finally Chandler’s TV Guide can be delivered to the right person. The obvious downside to this implementation is that the FullName calculation is duplicated in the database and in the UserProfile class. This sample was written using Visual Studio 2012 and Entity Framework 5. Download the source code here.

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  • Improve your Application Performance with .NET Framework 4.0

    Nice Article on CodeGuru. This processors we use today are quite different from those of just a few years ago, as most processors today provide multiple cores and/or multiple threads. With multiple cores and/or threads we need to change how we tackle problems in code. Yes we can still continue to write code to perform an action in a top down fashion to complete a task. This apprach will continue to work; however, you are not taking advantage of the extra processing power available. The best way to take advantage of the extra cores prior to .NET Framework 4.0 was to create threads and/or utilize the ThreadPool. For many developers utilizing Threads or the ThreadPool can be a little daunting. The .NET 4.0 Framework drastically simplified the process of utilizing the extra processing power through the Task Parallel Library (TPL). This article talks following topics “Data Parallelism”, “Parallel LINQ (PLINQ)” and “Task Parallelism”. span.fullpost {display:none;}

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  • Framework 4 Features: User Propogation to the Database

    - by Anthony Shorten
    Once of the features I mentioned in a previous entry was the ability for Oracle Utilities Application Framework V4 to automatically propogate the end user to the database connection. This bears more explanation. In the past releases of the Oracle Utilities Application Framework, all database connections are pooled and shared within a channel of access. So for example, the online connections on the Business Application Server share a common pool of connections and the batch in a thread pool shares a seperate pool of connections. The connections are pooled for performance reasons (the most expensive part of a typical transaction is opening and closing connections so we save time by having them ready beforehand). The idea is that when a business function needs some SQL to be execute it takes a spare connection from the pool, executes the SQL and then returns the connection back to the pool for reuse. Unfortunelty to support the pool being started and ready before the transactions arrives means that you need to have a shared userid (as you dont know the users who need them beforehand). Therefore each connection uses the same database user to execute the SQL it needs. This is acceptable for executing transactions, generally but does not allow the DBA or other tools to ascertain which end user is actually running the transaction. In Oracle Utilities Application Framework V4, we now set the CLIENT_IDENTIFIER to the end userid (not the Login Id) when the connection is taken from the pool and used and reset it back to blank when returned to the pool. The CLIENT_IDENTIFIER is a feature that is present in the Oracle Database connection information. From a monitoring perspective, when a connection to the database is actively running SQL, the end user is now able to be determined by querying the CLIENT_IDENTIFIER on the session object within the database. This can be done in the DBA's favorite monitoring tool (even just some SQL on the v$session table is enough). This has other implications as well. Oracle sells a lot of other security addons to the database and so do third parties. If a site wants to have additional levels of security or auditing in the database then the CLIENT_IDENTIFIER, if supported, is now available to be recorded or used by those products to provide additional levels of security. This facility was one of the highly "nice to haves" that customers would ask us about so we now allow it to be used to allow finer grained monitoring and additional security facilities. Note: This facility is only available for customers using the Oracle Database versions of our products.

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  • Cooperator Framework

    - by csharp-source.net
    Cooperator Framework is a base class library for high performance Object Relational Mapping (ORM), and a code generation tool that aids agile application development for Microsoft .Net Framework 2.0/3.0. The main features are: * Use business entities. * Full typed Model (Data Layer and Entities) * Maintain persistence across the layers by passing specific types( .net 2.0/3.0 generics) * Business objects can bind to controls in Windows Forms and Web Forms taking advantage of data binding of Visual Studio 2005. * Supports any Primary Key defined on tables, with no need to modify it or to create a unique field. * Uses stored procedures for data access. * Supports concurrency. * Generates code both for stored procedures and projects in C# or Visual Basic. * Maintains the model in a repository, which can be modified in any stage of the development cycle, regenerating the model on demand.

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  • Improve your Application Performance with .NET Framework 4.0

    Nice Article on CodeGuru. This processors we use today are quite different from those of just a few years ago, as most processors today provide multiple cores and/or multiple threads. With multiple cores and/or threads we need to change how we tackle problems in code. Yes we can still continue to write code to perform an action in a top down fashion to complete a task. This apprach will continue to work; however, you are not taking advantage of the extra processing power available. The best way to take advantage of the extra cores prior to .NET Framework 4.0 was to create threads and/or utilize the ThreadPool. For many developers utilizing Threads or the ThreadPool can be a little daunting. The .NET 4.0 Framework drastically simplified the process of utilizing the extra processing power through the Task Parallel Library (TPL). This article talks following topics “Data Parallelism”, “Parallel LINQ (PLINQ)” and “Task Parallelism”. span.fullpost {display:none;}

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  • Exam 70-518 Pro: Designing and Developing Windows Applications Using Microsoft .NET Framework 4

    - by Raghuraman Kanchi
    Today I noticed some topics from questions in the beta exam 70-518 which stumped me. I am just mentioning the topics below for future understanding and reference. This exam made me feel as if I was attempting questions about .NET 4.0 Framework. 1. Content-based vs. context-based filtered routing – Deciding the nearest Geographical Database. 2. Choosing an appropriate strategy for communicating with COM components, mainframe services 3. Microsoft Sync Framework 4. PLINQ 5. Difference between Dispatcher.BeginInvoke and Dispatcher.Invoke 6. Accessibility Testing/Scalability Testing (This objective may include but is not limited to: recommending functional testing, recommending reliability testing (performance testing, stress testing, scalability testing, duration testing)) 7. profiling, tracing, performance counters, audit trails 8. local vs. centralized reporting

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  • Free Version of Oracle Application Development Framework (Oracle ADF)

    - by Steve Muench
    I'm very happy to finally be able to talk about this. A long time coming, the press release is finally out: Oracle Introduces Free Version of Oracle Application Development Framework New Oracle ADF Essentials Brings ADF Benefits to the Broader Developer Community Oracle ADF Essentials is a free packaging of core technologies from the Oracle Application Development Framework that can be used to develop and deploy applications that include ADF Business Components, ADF Controller, ADF Binding, and ADF Faces Rich Client Components without incurring licensing costs. Both Oracle JDeveloper and Oracle Enterprise Pack for Eclipse provide visual and declarative development experience for using it. Oracle ADF Essentials comes with specific instructions and certification for deploying applications on the open-source Glassfish server, but the license is not limited to that server. For more information and to download it (it's only 20MB), see Oracle ADF Essentials page on OTN.

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  • Agile Entity Framework 4 Repository: Part 6: Mocks & Unit Tests

    I did finish this series, honest I did. But not in the blog. Ive shown this in a number of conferences and even in my book, but I never came back and wrote it all down. In fact, I had the whole solutino written before I began the series, but it has gone through a lot of changes. Where did I leave off? Agile Entity Framework 4 Repository: Part 1- Model and POCO Classes Agile Entity Framework 4 Repository: Part 2- The Repository Agile EF4 Repository: Part 3 -Fine Tuning the Repository Agile...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Attachment handling for web application with Jackrabbit

    - by Andrea Girardi
    I need to manage attachments on my Spring web application and I thought to use an open source repository. My app it's a job approval system using J2EE / SPRING 3 Framework and Postgress DB to allow user to tracks the job,right through every step of the approval process. It is a fully managed, collaborative system that operates from a central server and is accessed by a standard internet browser. An user should be able to add an attach to a request or an approval step, so, I though to use Jackrabbit with Postgres database persistence manager. I took a look to this post: http://onjava.com/pub/a/onjava/2006/10/04/what-is-java-content-repository.html?page=1 It's really interesting but, I've some question about this kind of solution :- I seen that Jackrabbit standalone as a Derby database embedded solution for persistence, is it enough for a professional use of the repository with more than 50 request / days (with attachment) ? Is there a reason for which I should use another database manager for persistence instead of the default one ?

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  • [News] Utiliser le framework de bouchon Moq

    Moq est un framework permettant de mettre en oeuvre les mock-objets destin?es aux phases de tests. Cet excellent article illustre le principe : " (...) it is intended to be straightforward and easy to use mocking framework that doesn?t require any prior knowledge of the mocking concepts. So, it doesn't requires deep learning curve from the developers. It takes full advantage of the .NET 3.5 expression trees and the lambda expressions. Any of the methods and properties of the mock object can be easily represented in the lambda expressions."

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  • Should a poll framework be closed sourced

    - by samquo
    I was having a chat with a coworker who is working on a polling app and framework. He was asking technical questions and I suggested he open source the application to get more quality opinions from developers who are interested in this problem and are willing to give it heavy though. He has a different point of view which I think is still valid so I want to open this question for discussion here. He says he believes something like a polling framework should not be open sourced because it will reduce its security and validity as people reveal loopholes through which they can cheat. Can't say I completely disagree. I see a somewhat valid point there, but I always believed that solutions by a group of people are almost always better than a solution thought by a single person asking a small number of coworkers, no matter how smart that person is. Again I'm willing to accept that maybe some types of applications are different. Does anyone have an argument in his favor? I'd really like to present your responses to him.

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