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  • Use Expressions with LINQ to Entities

    - by EltonStoneman
    [Source: http://geekswithblogs.net/EltonStoneman] Recently I've been putting together a generic approach for paging the response from a WCF service. Paging changes the service signature, so it's not as simple as adding a behavior to an existing service in config, but the complexity of the paging is isolated in a generic base class. We're using the Entity Framework talking to SQL Server, so when we ask for a page using LINQ's .Take() method we get a nice efficient SQL query for just the rows we want, with minimal impact on SQL Server and network traffic. We use the maximum ID of the record returned as a high-water mark (rather than using .Skip() to go to the next record), so the approach caters for records being deleted between page requests. In the paged response we include a HasMorePages indicator, computed by comparing the max ID in the page of results to the max ID for the whole resultset - if the latter is bigger, then there are more pages. In some quick performance testing, the paged version of the service performed much more slowly than the unpaged version, which was unexpected. We narrowed it down to the code which gets the max ID for the full resultset - instead of building an efficient MAX() SQL query, EF was returning the whole resultset and then computing the max ID in the service layer. It's easy to reproduce - take this AdventureWorks query:             var context = new AdventureWorksEntities();             var query = from od in context.SalesOrderDetail                         where od.ModifiedDate >= modified                          && od.SalesOrderDetailID.CompareTo(id) > 0                         orderby od.SalesOrderDetailID                         select od;   We can find the maximum SalesOrderDetailID like this:             var maxIdEfficiently = query.Max(od => od.SalesOrderDetailID);   which produces our efficient MAX() SQL query. If we're doing this generically and we already have the ID function in a Func:             Func<SalesOrderDetail, int> idFunc = od => od.SalesOrderDetailID;             var maxIdInefficiently = query.Max(idFunc);   This fetches all the results from the query and then runs the Max() function in code. If you look at the difference in Reflector, the first call passes an Expression to the Max(), while the second call passes a Func. So it's an easy fix - wrap the Func in an Expression:             Expression<Func<SalesOrderDetail, int>> idExpression = od => od.SalesOrderDetailID;             var maxIdEfficientlyAgain = query.Max(idExpression);   - and we're back to running an efficient MAX() statement. Evidently the EF provider can dissect an Expression and build its equivalent in SQL, but it can't do that with Funcs.

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  • Assessing Relative Maintainability

    - by João Bragança
    We (a contractor, actually) are implementing an off the shelf system to replace a legacy homegrown system for the core domain of the company (designing widgets). Unfortunately both systems will have to run concurrently for some time, as the product just isn't ready yet. Also, the decision was made to only migrate some of the widgets from the legacy system, based on date of last sale activity. Later on a new requirement came down: certain people in the company, most of them outside of the widget development context, want to search all widgets. The search results screen has 3 pieces of data: a GUID, a human readable id that is searchable, and a brief description (may need to be searchable in the future). In the widget details, there will be multiple screens. These screens align very well along SOA / bounded context lines - a screen for marketing data, a screen for sales history, etc. UML ahead! I am probably using the wrong kind of arrows here so please forgive me. The current solution - which is not in production yet - is something like the following: Both systems will be queried and the controller will merge the results. The new system has its own proprietary query language (we've alleviated this a bit with a LINQ provider). It also puts a lot of data on the wire. 15 search results typically run about 60k of unintelligible SOAP-wrapped xml. So I would prefer to avoid querying this system directly. These two systems publish events to help us integrate with other systems, mainly an ERP system. One of these events contains all the data necessary for the search screen. I proposed the following alternative: However I am being told that 'adding another database' will create more maintenance down the road. However, I believe this to be false, as I had to add a relatively simple feature that took several hours longer than anticipated because of this merging code. I want to get a feel for which system is more maintainable in the long run. I personally have not had the burden of maintaining any large system. I want something more than my gut. Specifically I'd like to know if having more, specialized physical databases is more or less maintainable than having less larger physical databases.

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  • Google I/O 2012 - Google Compute Engine -- Technical Details

    Google I/O 2012 - Google Compute Engine -- Technical Details Joe Beda, Evan Anderson This session will provide an in depth overview of Google Compute Engine. Google Compute provides Virtual Machines optimized for large scale data processing and analytics. We will dive into the core concepts, API, unique features and architectural best practices in the context of concrete examples. For all I/O 2012 sessions, go to developers.google.com From: GoogleDevelopers Views: 2497 88 ratings Time: 01:01:39 More in Science & Technology

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  • Annotation Processor for Superclass Sensitive Actions

    - by Geertjan
    Someone creating superclass sensitive actions should need to specify only the following things: The condition under which the popup menu item should be available, i.e., the condition under which the action is relevant. And, for superclass sensitive actions, the condition is the name of a superclass. I.e., if I'm creating an action that should only be invokable if the class implements "org.openide.windows.TopComponent",  then that fully qualified name is the condition. The position in the list of Java class popup menus where the new menu item should be found, relative to the existing menu items. The display name. The path to the action folder where the new action is registered in the Central Registry. The code that should be executed when the action is invoked. In other words, the code for the enablement (which, in this case, means the visibility of the popup menu item when you right-click on the Java class) should be handled generically, under the hood, and not every time all over again in each action that needs this special kind of enablement. So, here's the usage of my newly created @SuperclassBasedActionAnnotation, where you should note that the DataObject must be in the Lookup, since the action will only be available to be invoked when you right-click on a Java source file (i.e., text/x-java) in an explorer view: import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import org.netbeans.sbas.annotations.SuperclassBasedActionAnnotation; import org.openide.awt.StatusDisplayer; import org.openide.loaders.DataObject; import org.openide.util.NbBundle; import org.openide.util.Utilities; @SuperclassBasedActionAnnotation( position=30, displayName="#CTL_BrandTopComponentAction", path="File", type="org.openide.windows.TopComponent") @NbBundle.Messages("CTL_BrandTopComponentAction=Brand") public class BrandTopComponentAction implements ActionListener { private final DataObject context; public BrandTopComponentAction() { context = Utilities.actionsGlobalContext().lookup(DataObject.class); } @Override public void actionPerformed(ActionEvent ev) { String message = context.getPrimaryFile().getPath(); StatusDisplayer.getDefault().setStatusText(message); } } That implies I've created (in a separate module to where it is used) a new annotation. Here's the definition: package org.netbeans.sbas.annotations; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; @Retention(RetentionPolicy.SOURCE) @Target(ElementType.TYPE) public @interface SuperclassBasedActionAnnotation { String type(); String path(); int position(); String displayName(); } And here's the processor: package org.netbeans.sbas.annotations; import java.util.Set; import javax.annotation.processing.Processor; import javax.annotation.processing.RoundEnvironment; import javax.annotation.processing.SupportedAnnotationTypes; import javax.annotation.processing.SupportedSourceVersion; import javax.lang.model.SourceVersion; import javax.lang.model.element.Element; import javax.lang.model.element.TypeElement; import javax.lang.model.util.Elements; import org.openide.filesystems.annotations.LayerBuilder.File; import org.openide.filesystems.annotations.LayerGeneratingProcessor; import org.openide.filesystems.annotations.LayerGenerationException; import org.openide.util.lookup.ServiceProvider; @ServiceProvider(service = Processor.class) @SupportedAnnotationTypes("org.netbeans.sbas.annotations.SuperclassBasedActionAnnotation") @SupportedSourceVersion(SourceVersion.RELEASE_6) public class SuperclassBasedActionProcessor extends LayerGeneratingProcessor { @Override protected boolean handleProcess(Set annotations, RoundEnvironment roundEnv) throws LayerGenerationException { Elements elements = processingEnv.getElementUtils(); for (Element e : roundEnv.getElementsAnnotatedWith(SuperclassBasedActionAnnotation.class)) { TypeElement clazz = (TypeElement) e; SuperclassBasedActionAnnotation mpm = clazz.getAnnotation(SuperclassBasedActionAnnotation.class); String teName = elements.getBinaryName(clazz).toString(); String originalFile = "Actions/" + mpm.path() + "/" + teName.replace('.', '-') + ".instance"; File actionFile = layer(e).file( originalFile). bundlevalue("displayName", mpm.displayName()). methodvalue("instanceCreate", "org.netbeans.sbas.annotations.SuperclassSensitiveAction", "create"). stringvalue("type", mpm.type()). newvalue("delegate", teName); actionFile.write(); File javaPopupFile = layer(e).file( "Loaders/text/x-java/Actions/" + teName.replace('.', '-') + ".shadow"). stringvalue("originalFile", originalFile). intvalue("position", mpm.position()); javaPopupFile.write(); } return true; } } The "SuperclassSensitiveAction" referred to in the code above is unchanged from how I had it in yesterday's blog entry. When I build the module containing two action listeners that use my new annotation, the generated layer file looks as follows, which is identical to the layer file entries I hard coded yesterday: <folder name="Actions"> <folder name="File"> <file name="org-netbeans-sbas-impl-ActionListenerSensitiveAction.instance"> <attr name="displayName" stringvalue="Process Action Listener"/> <attr methodvalue="org.netbeans.sbas.annotations.SuperclassSensitiveAction.create" name="instanceCreate"/> <attr name="type" stringvalue="java.awt.event.ActionListener"/> <attr name="delegate" newvalue="org.netbeans.sbas.impl.ActionListenerSensitiveAction"/> </file> <file name="org-netbeans-sbas-impl-BrandTopComponentAction.instance"> <attr bundlevalue="org.netbeans.sbas.impl.Bundle#CTL_BrandTopComponentAction" name="displayName"/> <attr methodvalue="org.netbeans.sbas.annotations.SuperclassSensitiveAction.create" name="instanceCreate"/> <attr name="type" stringvalue="org.openide.windows.TopComponent"/> <attr name="delegate" newvalue="org.netbeans.sbas.impl.BrandTopComponentAction"/> </file> </folder> </folder> <folder name="Loaders"> <folder name="text"> <folder name="x-java"> <folder name="Actions"> <file name="org-netbeans-sbas-impl-ActionListenerSensitiveAction.shadow"> <attr name="originalFile" stringvalue="Actions/File/org-netbeans-sbas-impl-ActionListenerSensitiveAction.instance"/> <attr intvalue="10" name="position"/> </file> <file name="org-netbeans-sbas-impl-BrandTopComponentAction.shadow"> <attr name="originalFile" stringvalue="Actions/File/org-netbeans-sbas-impl-BrandTopComponentAction.instance"/> <attr intvalue="30" name="position"/> </file> </folder> </folder> </folder> </folder>

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  • Ubuntu ONE (Windows BETA) locks up - What to do?

    - by Zusch
    OS: Windows XP SP3 Hardware: Dell Precision M4400 (Laptop) CPU: Core2Duo T9600 Mem: 4 GB Installer- setup, first start and account- setup of UbuntuONE Windows client passed with no problems. After restart of UbuntuONE, the CPU- usage shows 50% (100% core usage). Exit- command (from context-menu) hides the trayicon, but the program is still working excessive in background (50% cpu- / 50 MB memory- usage), until UbuntuOneClient.exe is killed by the taskmanager. What's going on ?

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  • Beginner: How to Run an Application as Administrator in Windows 8

    - by Taylor Gibb
    Windows 8 does away with the Start Menu we all know and love, and introduces a more “immersive” Start Screen. Since there’s no context menu on the Start Screen you may be wondering how to run applications as administrator–here’s how. HTG Explains: What Is RSS and How Can I Benefit From Using It? HTG Explains: Why You Only Have to Wipe a Disk Once to Erase It HTG Explains: Learn How Websites Are Tracking You Online

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  • Pseudo-magnet implementation with chipmunk

    - by Eimantas
    How should I go about implementing "natural" magnet on a certain body in chipmunk space? Context is of simple bodies lying in the space (think chessboard). When one of the figures is activated as a magnet - others should start moving towards it. Currently I'm applying force (cpBodyApplyForce)to the other figures with vector calculated towards the activated figure. However this doesn't really feel "natural". Are there any known algorithms for imitating magnets?

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  • Nautilus-Action conf. tool - crafting a "set as background" action

    - by EgyptBeast
    I wanted to create an option in the context menu to set the clicked picture to current desktop background (just like in Windows). I read the the nautilus action help but I couldn't figure it out. This is by far the command I could craft: gsettings set org.gnome.desktop.background picture-uri file://$PWD/ What I need: A command that correctly sets the current image to be the desktop background This command should only appear to the proper files (picture extenstions like .jpg)

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  • Oracle SRM increases enterprise footprint with Eloqua integration: an Ovum report

    - by Richard Lefebvre
    At Oracle OpenWorld in September, Oracle announced that Social Relationship Management (SRM) suite is further integrated with Oracle Eloqua, its newly acquired marketing automation platform. "Oracle is the only leading vendor to date to have fully integrated social with a sales lead management platform within the context of marketing automation" writes Gerry Brown in this Ovum report, in which you can read and understand all the benefits of this integration,

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  • Ubuntu One Music Store: Tops or Flop?

    <b>Linux Pro Magazine:</b> "Thus Canonical is implementing the cloud in its context. The DRM-free songs in MP3 format with a bitrate of at least 256 kbits/second are not loaded on the local machine, but in the Ubuntu One cloud."

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  • Does it make sense to implement OAuth for a 2 party system?

    - by nbv4
    I'm under the impression that OAuth is for authentication between three parties. Does it make sense to implement OAuth in a context where there is just a client and server. We have a server, and a client (HTML/javascript). Currently we authenticate via the normal "post credentials to server, get a cookie, use cookie to authenticate all subsequent requests" method. Will implementing OAuth be a benefit in this situation?

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  • ArchBeat Link-o-Rama for 10-24-2012

    - by Bob Rhubart
    Play Oracle Vanquisher Here's a little respite from whatever it is you normally spend your time on. Oracle Vanquisher is an online diversion that makes a game of data center optimization. According to the description: "Armed with a cool Oracle vacuum pack suit and a strategic IT roadmap, you will thwart threats and optimize your data center to increase your company’s stock price and boost your company's position." Mainly you avoid electric shock and killer birds. The current high score belongs to someone identified as "TEN." My score? Never mind. Book: DevOps for Developers | The Java Source The subject of DevOps has come up in a couple of recent OTN ArchBeat Podcasts, so it's somewhat serendipitous that Tori Weildt's recent blog post offers an overview of Java Champion Michael Hutterman's new book, DevOps for Developers, now available from Apress. Bring Your Own Device (BYOD) : Context is everything… | The ORACLE-BASE Blog BOYD is a factor in the evolution of IT, but in what context? "The real IT work in companies is still being done on PCs," says Oracle ACE Director Tim Hall. "Yes, you can use a cloud service on your phone, but look around the office and you will see those cloud services are actually being used by people on PCs." Oracle in the Cloud: Oracle EBusiness Suite sizing | Tom Laszewski Cloud expert Tom Laszewski shares several technical resources that will be helpful for sizing of Oracle EBusiness Suite. Setting Up, Configuring, and Using an Oracle WebLogic Server Cluster Author and expert Yuli Vasiliev shows you how take advantage of multiple Oracle WebLogic Server instances grouped into a cluster to maximize scalability and availability. Webcast: Reduce Costs with Oracle's Database Storage Management Watch this! Join Oracle experts Kevin Jernigan and Margaret Hamburger for an interactive webcast in which you'll learn how Oracle's Database Storage Management can reduce storage costs and management complexity while improving query performance to meet service-level agreements and compliance requirements. Event Date: Tuesday, November 6, 2012 Event Time: 10 a.m. PT/1 p.m. ET Thought for the Day "Most software today is very much like an Egyptian pyramid with millions of bricks piled on top of each other, with no structural integrity, but just done by brute force and thousands of slaves." — Alan Kay Source: softwarequotes.com

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  • Test-only Members: Good or Bad?

    In the article, Dino focuses on two particular situations: dealing with dependencies and testing private members. He'll be discussing this in the context of ASP.NET MVC and MSTest, but without any significant loss of generality.

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  • HTML5 - check if font has loaded

    - by espais
    At present I load my font for my game in with @font-face For instance: @font-face { font-family: 'Orbitron'; src: url('res/orbitron-medium.ttf'); } and then reference it throughout my JS implementation as such: ctx.font = "12pt Orbitron"; where ctx is my 2d context from the canvas. However, I notice a certain lag time while the font is downloaded to the user. Is there a way I can use a default font until it is loaded in?

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  • How do I succesfully compile Slingshot?

    - by Tigull
    I've been trying to compile Slingshot for a preview of Elementary OS. Even after replacing Gtk.Stock.CLEAR and Gtk.Stock.add with Gtk.STOCK_CLEAR and Gtk.Stock_add in slingshot/widget/entries .vala I still get the following error when executing sudo ./build_run: frontend/widgets/Entries.vala:130.13-130.25: error: The name `Stock_add' does not exist in the context of `Gtk' Gtk.Stock_add ({stock_item}); ^^^^^^^^^^^^^ Compilation failed: 1 error(s), 0 warning(s) mv: cannot stat `slingshot': No such file or directory ./build_run: 7: slingshot: not found I haven't found yet a soulution, therefore any help is appreciated, thanks!

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  • What is going on in this SAT/vector projection code?

    - by ssb
    I'm looking at the example XNA SAT collision code presented here: http://www.xnadevelopment.com/tutorials/rotatedrectanglecollisions/rotatedrectanglecollisions.shtml See the following code: private int GenerateScalar(Vector2 theRectangleCorner, Vector2 theAxis) { //Using the formula for Vector projection. Take the corner being passed in //and project it onto the given Axis float aNumerator = (theRectangleCorner.X * theAxis.X) + (theRectangleCorner.Y * theAxis.Y); float aDenominator = (theAxis.X * theAxis.X) + (theAxis.Y * theAxis.Y); float aDivisionResult = aNumerator / aDenominator; Vector2 aCornerProjected = new Vector2(aDivisionResult * theAxis.X, aDivisionResult * theAxis.Y); //Now that we have our projected Vector, calculate a scalar of that projection //that can be used to more easily do comparisons float aScalar = (theAxis.X * aCornerProjected.X) + (theAxis.Y * aCornerProjected.Y); return (int)aScalar; } I think the problems I'm having with this come mostly from translating physics concepts into data structures. For example, earlier in the code there is a calculation of the axes to be used, and these are stored as Vector2, and they are found by subtracting one point from another, however these points are also stored as Vector2s. So are the axes being stored as slopes in a single Vector2? Next, what exactly does the Vector2 produced by the vector projection code represent? That is, I know it represents the projected vector, but as it pertains to a Vector2, what does this represent? A point on a line? Finally, what does the scalar at the end actually represent? It's fine to tell me that you're getting a scalar value of the projected vector, but none of the information I can find online seems to tell me about a scalar of a vector as it's used in this context. I don't see angles or magnitudes with these vectors so I'm a little disoriented when it comes to thinking in terms of physics. If this final scalar calculation is just a dot product, how is that directly applicable to SAT from here on? Is this what I use to calculate maximum/minimum values for overlap? I guess I'm just having trouble figuring out exactly what the dot product is representing in this particular context. Clearly I'm not quite up to date on my elementary physics, but any explanations would be greatly appreciated.

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  • Are closures with side-effects considered "functional style"?

    - by Giorgio
    Many modern programming languages support some concept of closure, i.e. of a piece of code (a block or a function) that Can be treated as a value, and therefore stored in a variable, passed around to different parts of the code, be defined in one part of a program and invoked in a totally different part of the same program. Can capture variables from the context in which it is defined, and access them when it is later invoked (possibly in a totally different context). Here is an example of a closure written in Scala: def filterList(xs: List[Int], lowerBound: Int): List[Int] = xs.filter(x => x >= lowerBound) The function literal x => x >= lowerBound contains the free variable lowerBound, which is closed (bound) by the argument of the function filterList that has the same name. The closure is passed to the library method filter, which can invoke it repeatedly as a normal function. I have been reading a lot of questions and answers on this site and, as far as I understand, the term closure is often automatically associated with functional programming and functional programming style. The definition of function programming on wikipedia reads: In computer science, functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions, in contrast to the imperative programming style, which emphasizes changes in state. and further on [...] in functional code, the output value of a function depends only on the arguments that are input to the function [...]. Eliminating side effects can make it much easier to understand and predict the behavior of a program, which is one of the key motivations for the development of functional programming. On the other hand, many closure constructs provided by programming languages allow a closure to capture non-local variables and change them when the closure is invoked, thus producing a side effect on the environment in which they were defined. In this case, closures implement the first idea of functional programming (functions are first-class entities that can be moved around like other values) but neglect the second idea (avoiding side-effects). Is this use of closures with side effects considered functional style or are closures considered a more general construct that can be used both for a functional and a non-functional programming style? Is there any literature on this topic? IMPORTANT NOTE I am not questioning the usefulness of side-effects or of having closures with side effects. Also, I am not interested in a discussion about the advantages / disadvantages of closures with or without side effects. I am only interested to know if using such closures is still considered functional style by the proponent of functional programming or if, on the contrary, their use is discouraged when using a functional style.

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  • Is return-type-(only)-polymorphism in Haskell a good thing?

    - by dainichi
    One thing that I've never quite come to terms with in Haskell is how you can have polymorphic constants and functions whose return type cannot be determined by their input type, like class Foo a where foo::Int -> a Some of the reasons that I do not like this: Referential transparency: "In Haskell, given the same input, a function will always return the same output", but is that really true? read "3" return 3 when used in an Int context, but throws an error when used in a, say, (Int,Int) context. Yes, you can argue that read is also taking a type parameter, but the implicitness of the type parameter makes it lose some of its beauty in my opinion. Monomorphism restriction: One of the most annoying things about Haskell. Correct me if I'm wrong, but the whole reason for the MR is that computation that looks shared might not be because the type parameter is implicit. Type defaulting: Again one of the most annoying things about Haskell. Happens e.g. if you pass the result of functions polymorphic in their output to functions polymorphic in their input. Again, correct me if I'm wrong, but this would not be necessary without functions whose return type cannot be determined by their input type (and polymorphic constants). So my question is (running the risk of being stamped as a "discussion quesion"): Would it be possible to create a Haskell-like language where the type checker disallows these kinds of definitions? If so, what would be the benefits/disadvantages of that restriction? I can see some immediate problems: If, say, 2 only had the type Integer, 2/3 wouldn't type check anymore with the current definition of /. But in this case, I think type classes with functional dependencies could come to the rescue (yes, I know that this is an extension). Furthermore, I think it is a lot more intuitive to have functions that can take different input types, than to have functions that are restricted in their input types, but we just pass polymorphic values to them. The typing of values like [] and Nothing seems to me like a tougher nut to crack. I haven't thought of a good way to handle them. I doubt I am the first person to have had thoughts like these. Does anybody have links to good discussions about this Haskell design decision and the pros/cons of it?

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  • Easy QueryBuilder - A User-Friendly Ad-Hoc Advanced Search Solution

    Constructing an easy and powerful QueryBuilder interface becomes more important for complex data grid filtering and accurate reporting services. In this article, I'll discuss how to build a query search engine using ASP.NET AJAX and dynamic SQL. The main goal is to provide an interactive interface to allow users select query attributes, operators, attribute values, and T-SQL operators so that the data context query list can be easily composed and a search engine is invoked.

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  • Securing the Tabular BI Semantic Model

    This paper introduces the security model for tabular BI semantic models in SQL Server 2012. You will learn how to create roles, implement dynamic security, configure impersonation settings, manage roles, and choose a method for connecting to models that works in your network security context. New! SQL Monitor 3.0 Red Gate's multi-server performance monitoring and alerting tool gets results from Day One.Simple to install and easy to use – download a free trial today.

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  • [EF + Oracle] Inserting Data (1/2)

    - by JTorrecilla
    Prologue Following EF series (I ,II y III) in this chapter we will see how to create DB record from EF. Inserting Data Like we indicated in the 2º post: “One Entity matches with a DB record, and one property match with a Table Column”. To start, we need to create an object from one of the Entities: 1: EMPLEADOS empleado = new EMPLEADOS(); Also like, I told previously, Exists the possibility to use the Static Function defined by VS for each Entity: Once we have created the object, we can Access to it properties to fill like a common class:   1: empleado.NOMBRE = "Javier Torrecilla";   After finish of fill our Entity properties, it must be needed to add the object to the appropriate ObjectSet in the ObjectContext: 1: enti.EMPLEADOS.AddObject(empleado); or 1: enti.AddToEMPLEADOS(empleado); Both methods will do the same action, create an insert statement. Have we finished? No. Any Entity has a property called “EntityState”. This prop is an Enum from “EntityState”, which has the following: Detached: the Entity is created, but not added to the Context. Unchanged: There is no pending changes in the Entity. Added: The entity is added to the ObjectSet, but it is not yet sent to the DB. Deleted: The object is deleted form the ObjectSet, but not yet from the DB. Modified: There is Pending Changes to confirm. Let’s see, the several values of the property during the Creation steps: 1. While the Object is created and we are filling the props: EntityState.Detached; 2. After adding to the ObjectSet: EntityState.Added. This not indicated that the record is in the DB 3. Saving the Data: To sabe the data in the DB, we are going to call “SaveChanges” method of the Object Context. After invoke it, the property will be EntityState.Unchanged.   What does SaveChanges Method? This function will synchronize and send all pending changes to DB. It will add, modify or delete all Entities, whose EntityState property, is setted to Added, Deleted or Modified. After finishing, all added or modified entities will be change the State to “Unchanged”, and deleted Entities must take the “Detached” state.

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  • Entity Framework 5, separating business logic from model - Repository?

    - by bnice7
    I am working on my first public-facing web application and I’m using MVC 4 for the presentation layer and EF 5 for the DAL. The database structure is locked, and there are moderate differences between how the user inputs data and how the database itself gets populated. I have done a ton of reading on the repository pattern (which I have never used) but most of my research is pushing me away from using it since it supposedly creates an unnecessary level of abstraction for the latest versions of EF since repositories and unit-of-work are already built-in. My initial approach is to simply create a separate set of classes for my business objects in the BLL that can act as an intermediary between my Controllers and the DAL. Here’s an example class: public class MyBuilding { public int Id { get; private set; } public string Name { get; set; } public string Notes { get; set; } private readonly Entities _context = new Entities(); // Is this thread safe? private static readonly int UserId = WebSecurity.GetCurrentUser().UserId; public IEnumerable<MyBuilding> GetList() { IEnumerable<MyBuilding> buildingList = from p in _context.BuildingInfo where p.Building.UserProfile.UserId == UserId select new MyBuilding {Id = p.BuildingId, Name = p.BuildingName, Notes = p.Building.Notes}; return buildingList; } public void Create() { var b = new Building {UserId = UserId, Notes = this.Notes}; _context.Building.Add(b); _context.SaveChanges(); // Set the building ID this.Id = b.BuildingId; // Seed 1-to-1 tables with reference the new building _context.BuildingInfo.Add(new BuildingInfo {Building = b}); _context.GeneralInfo.Add(new GeneralInfo {Building = b}); _context.LocationInfo.Add(new LocationInfo {Building = b}); _context.SaveChanges(); } public static MyBuilding Find(int id) { using (var context = new Entities()) // Is this OK to do in a static method? { var b = context.Building.FirstOrDefault(p => p.BuildingId == id && p.UserId == UserId); if (b == null) throw new Exception("Error: Building not found or user does not have access."); return new MyBuilding {Id = b.BuildingId, Name = b.BuildingInfo.BuildingName, Notes = b.Notes}; } } } My primary concern: Is the way I am instantiating my DbContext as a private property thread-safe, and is it safe to have a static method that instantiates a separate DbContext? Or am I approaching this all wrong? I am not opposed to learning up on the repository pattern if I am taking the total wrong approach here.

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  • Secure Your Future While Sitting at Home

    Gaining education and then achieving a quality degree is thought to be a very devoting and scheduled task in previous times. People set aims and then strive for it the whole of their lives. The aim or goal which would be taken in the context of professional status or qualification over here was usually a typical profession which was famous at the hour.

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