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  • Which layer should create DataContext?

    - by Kevin
    I have a problem to decide which layer in my system should create DataContext. I have read a book, saying that if do not pass the same DataContext object for all the database updates, it will sometimes get an exception thrown from the DataContext. That's why i initially create new instance of DataContext in business layer, and pass it into data access layer. So that the same datacontext is used for all the updates. But this lead to one design problem, if i wanna change my DAL to Non-LinqToSQL in future, i need to re-write the code in business layer as well. Please give me some advice on this. Thanks. Example code 'Business Layer Public Sub SaveData(name As String) Using ts AS New TransactionScope() Using db As New MyDataContext() DAL.Insert(db,name) DAL.Insert(db,name) End Using ts.Complete() End Using End Sub 'Data Access Layer Public Sub Insert(db as MyDataContext,name As string) db.TableAInsert(name) End Sub

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  • C# Process flow - Datastream, XML and datagrid

    - by Farstucker
    Im looking for some advice/suggestions on how I should setup the work flow of a small application Im building. When the application is launched the datagrid will be populated via the XML file. Once running the application will receive a datastream that I hope to update the file and datagrid. So Im curious what you would suggest on how I setup the workflow (ie, split the data from the data stream and simultaneously populate the file and grid or would you suggest populating the XML file first and setting up a timer to have the grid read the file?) Im really looking for optimal performance.

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  • What is the relationship between Turing Machine & Modern Computer ?

    - by smwikipedia
    I heard a lot that modern computers are based on Turing machine. I just cannot build a bridge from a conceptual Turing Machine to a real modern computer. Could someone help me build this bridge? Below is my current understanding. I think the computer is a big general-purpose Turing machine. Each program we write is a small specific-purpose Turing machine. The classical Turing machine do its job based on the input and its current state inside and so do our programs. Let's take a running program (a process) as an example. We know that in the process's address space, there's areas for stack, heap, and code. A classical Turing machine doesn't have the ability to remember many things, so we borrow the concept of stack from the push-down automaton. The heap and stack areas contains the state of our specific-purpose Turing machine (our program). The code area represents the logic of this small Turing machine. And various I/O devices supply input to this Turing machine.

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  • How much business logic belongs in RIA services layer?

    - by jkohlhepp
    I have been experimenting recently with Silverlight, RIA Services, and Entity Framework using .NET 4.0. I'm trying to figure out if that stack makes sense for use in any of my upcoming projects. It certainly seems like these technologies can be very productive for developing applications, but I'm struggling to decide how an application on top of this stack should be architected. The main issue I have is that in most of the demos I've seen most of the business logic ends up as DataAnnotations and custom validations in the RIA Services domain service class. This seems inappropriate to me. I view the domain service as basically a glorified web service that happens to make it easy to push information to the client. But most of what I've seen seems to orient the domain service as the main source of business logic in the application. So, my questions: What is the best location for business logic (rules, validations, behaviors, authorization) in an application using this stack? Are there any guidelines published at an architectural level for using this stack? My questions pertain to large, complex, and long-lived applications. Obviously for an application of only a few screens this is less of a concern. Edit: Another thing I meant to mention is that obviously you can make the domain service class stupid, but then you lose a lot of the automagic entity information (e.g. validations) being pushed to the client. And then if you lose that is there any point to using RIA services?

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  • Considerations when architecting an extensible application using MEF

    - by Dan Bryant
    I've begun experimenting with dependency injection (in particular, MEF) for one of my projects, which has a number of different extensibility points. I'm starting to get a feel for what I can do with MEF, but I'd like to hear from others who have more experience with the technology. A few specific cases: My main use case at the moment is exposing various singleton-like services that my extensions make use of. My Framework assembly exposes service interfaces and my Engine assembly contains concrete implementations. This works well, but I may not want to allow all of my extensions to have access to all of my services. Is there a good way within MEF to limit which particular imports I allow a newly instantiated extension to resolve? This particular application has extension objects that I repeatedly instantiate. I can import multiple types of Controllers and Machines, which are instantiated in different combinations for a Project. I couldn't find a good way to do this with MEF, so I'm doing my own type discovery and instantiation. Is there a good way to do this within MEF or other DI frameworks? I welcome input on any other things to watch out for or surprising capabilities you've discovered that have changed the way you architect.

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  • Need some help/advice on WCF Per-Call Service and NServiceBus interop.

    - by Alexey
    I have WCF Per-Call service wich provides data for clients and at the same time is integrated with NServiceBus. All statefull objects are stored in UnityContainer wich is integrated into custom service host. NServiceBus is configured in service host and uses same container as service instances. Every client has its own instance context(described by Juval Lowy in his book in chapter about Durable Services). If i need to send request over bus I just use some kind of dispatcher and wait response using Thread.Sleep().Since services are per-call this is ok afaik. But I am confused a bit about messages from bus, that service must handle and provide them to clients. For some data like stock quotes I just update some kind of statefull object and and then, when clients invoke GetQuotesData() just provide data from this object. But there are numerous service messages like new quote added and etc. At this moment I have an idea to implement something like "Postman daemon" =)) and store this type of messages in instance context. Then client will invoke "GetMail()",recieve those messages and parse them. Problem is that NServiceBus messages are "Interface based" and I cant pass them over WCF, so I need to convert them to types derieved from some abstract class. Dunno what is best way to handle this situation. Will be very gratefull for any advice on this. Thanks in advance.

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  • How do I send an XML document to an ASP.NET MVC page for manipuation

    - by Decker
    I have some hierarchical data stored as an multiple XML files on the server according to a vendor's schema. In my ASP.NET MVC (2!) application, I'd like the user to choose one of these hierarchies (i.e. file -- I provide a list in my controller's Index action). When the user selects one to "edit" my edit action should return a page that presents the XML hierarchy (it's a representation of a folder tree). So my thoughts are that the view would return HTML that contained a JQuery on load ajax call back to the server for the XML data -- at which point I would present the tree using one of the many JQuery tree controls. On the client side I'd like the user to manipulate the tree and when done, I'd like to post back the new hierarchy where I would replace the original XML file that represents that hierarchy. So my questions are: What form should I use to send the data down? XML or JSON?. If I send down XML then I would have to not only read the XML -- which JQuery can do -- but I would also have to be able to modify that XML and then send it back. Can I use JQuery to modify this XML DOM? And will all the namespace declarations be preserved? What form should I send the data back? If I originally sent the client the hierarchy as JSON (using JsonResult), then presumably I would have a hierarchy of javascript objects. What options would I have to post that back? Would I have to recreate the XML reprentation on the client and post that back? Or should I serialize back to JSON, post that to the server, and then have the server do the work of recreating the XML according to the schema. Thanks for any advice.

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  • How do you use Linq2Sql in your applications ?

    - by this. __curious_geek
    I'm recently migrating to Linq2Sql and all my future projects would be done in Linq2Sql. Having said that, I researched a lot on how to properly plug-in Linq2Sql in application design. what to put at what layer ? Should I use DTOs over Linq2Sql entities ? I did not find any rock-solid material that really talked about one single thing and everyone had their own opinions and I found all of them justified right from their arguments. I'm looking forward to your ideas on how to integrate/use Linq2Sql in projects. My priority is maintenance[it should be maintenable and when multiple people work on same project] and scalabilty [it should have scope of evolution]. Thanks.

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  • Mimic remote API or extend existing django model

    - by drozzy
    I am in a process of designing a client for a REST-ful web-service. What is the best way to go about representing the remote resource locally in my django application? For example if the API exposes resources such as: List of Cars Car Detail Car Search Dealership summary So far I have thought of two different approaches to take: Try to wrangle the django's models.Model to mimic the native feel of it. So I could try to get some class called Car to have methods like Car.objects.all() and such. This kind of breaks down on Car Search resources. Implement a Data Access Layer class, with custom methods like: Car.get_all() Car.get(id) CarSearch.search("blah") So I will be creating some custom looking classes. Has anyone encoutered a similar problem? Perhaps working with some external API's (i.e. twitter?) Any advice is welcome. PS: Please let me know if some part of question is confusing, as I had trouble putting it in precise terms.

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  • What is the big deal with IQueryable?

    - by jjr2527
    I've seen a lot of people talking about IQueryable and I haven't quite picked up on what all the buzz is about. I always work with generic List's and find they are very rich in the way you can "query" them and work with them, even run LINQ queries against them. So I'm wondering if there is a good reason to start considering a different default collection in my projects.

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  • Providing multi-version databases for backward compatibility for production applications/databases.

    - by JavaRocky
    How can I manage multiple versions of a database easily? I have some data (as views as selects for data originating in tables from other schemas), which other database may reference using various means including database synonyms & links. I wish to provide a sort of interface/guarantee in-case future for applications/databases which use this data. All of this is for in the event i need to update the views for correctness or applicability inside my database. How can i achieve this in a maintained, controlled and easy way? I am using Oracle 10g if that matters.

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  • What is the best folder stucture in TFS for reporting service projects

    - by Dave
    Hi, I'm looking for some help on deciding a useful folder stucture strategy for reporting service projects in TFS. Does any one have some suggestions on which way I should stucture TFS? Should it be a project per report or should it be one Reporting project with multiple folders under the main that contain all the report projects? i.e. Senario 1 (separate projects for each report project) $ReportProject1 $ReportProject2 $ReportProject3 Senario 2 (Main report project in TFS and subfolders with report projects) $ReportingServices ------Src ---------Project1 -----------ReportProject1 files ---------Project2 -----------ReportProject2 files ---------Project3 -----------ReportProject3 files

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  • Data Access Layer, Best Practices

    - by labratmatt
    I'm looking for input on the best way to refactor the data access layer (DAL) in my PHP based web app. I follow an MVC pattern: PHP/HTML/CSS/etc. views on the front end, PHP controllers/services in the middle, and a PHP DAL sitting on top of a relational database in the model. Pretty standard stuff. Things are working fine, but my DAL is getting large (codesmell?) and becoming a bit unwieldy. My DAL contains almost all of the logic to interface with my database and is full of functions that look like this: function getUser($user_id) { $statement = "select id, name from users where user_id=:user_id"; PDO builds statement and fetchs results as an array return $array_of_results_generated_by_PDO_fetch_method; } Notes: The logic in my controller only interacts with the model using functions like the above in the DAL I am not using a framework (I'm of the opinion that PHP is a templating language and there's no need to inject complexity via a framework) I generally use PHP as a procedural language and tend to shy away from its OOP approach (I enjoy OOP development but prefer to keep that complexity out of PHP) What approaches have you taken when your DAL has reached this point? Do I have a fundamental design problem? Do I simply need to chop my DAL into a number of smaller files (logically divide it)? Thanks.

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  • Architectural conundrum

    - by Dejan
    The worst thing when working on a one man project is the lack of input that you usually get from your coworkers. And because of the lack of that you tend to make obvious mistakes. After going down that road for some time I would need some help from the community. I started a little home-brew project that should turn into a portal of some sorts. And the main thing that is bothering me is the persistence layer that i have concocted. It should be completely separated from the presentation layer for starters and a OR mapper is also somewhere. This is because I have multiple data stores that have to be used. So the base idea was that the individual "repositories" operate each on their individual database and that the business layer then aggregates the business objects which are then transformed in the presentation layer into view objects. The main problem I face is the following: Multiple classes for the same concept - There is a DAL representation of a user and BL representation of user and a view representation of a user. I can handle the transformation with a tool but is this really the right way. I mean they are all nicely separated, but the overhead is quite something. What do you think? Am I going too deep into the separation of concern rabbit hole or is this still normal?

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  • How to map different UI views in a RESTful web application?

    - by MicE
    Hello, I'm designing a web application, which will support both standard UIs (accessed via browsers) and a RESTful API (an XML/JSON-based web service). User agents will be able to differentiate between these by using different values in the Accept HTTP header. The RESTful API will use the following URI structure (example for an "article" resource): GET /article/ - gets a list of articles POST /article/ - adds a new article PUT /article/{id} - updates an existing article based on {id} DELETE /article/{id} - deletes an existing article based on {id} The UI part of the application will however need to support multiple views, for example: a standard resource view a view for submitting a new resource a view for editing an existing resource a view for deleting an existing resource (i.e. display delete confirmation) Note that the latter three views are still accessed via GET, even though they are processed via overloaded POST. Possible solution: Introduce additional parameters (keywords) into URIs which would identify individual views - i.e. on top of the above, the application would support the following URIs (but only for Content-Type: text/html): GET /article/add - displays a form for adding a new article (fetched via GET, processed via POST) GET /article/123 - displays article 123 in "view" mode (fetched via GET) GET /article/123/edit - displays article 123 in "edit" mode (fetched via GET, processed via PUT overloaded as POST) GET /article/123/delete - displays "delete" confirmation for article 123 (fetched via GET, processed via DELETE overloaded as POST) A better implementation of the above might be to put the add/edit/delete keywords into a GET parameter - since they do not change the resource we're working with, it might be better to keep the base URI same for all of them. My question is: How would you map the above URI structure to UIs served to the regular user, considering that there can be several views per each resource, please? Do you agree with the possible solution detailed above, or would you recommend a different approach based on your experience? NB: we've already implemented an application which consists of a standalone RESTful API and a standalone web application. I'm currently looking into options for future projects where these two would be merged together (i.e. in order to reduce overhead). Thank you, M.

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  • Verbose Listing of All Application Layers/Tiers?

    - by leeand00
    I've looked at a few sites now, and I'm still struggling to find a complete listing of all the possible layers/tiers you can have in an application. From back in college (1999) I remember the following: Presentation Layer (Views) Application Layer (Controllers) Business Logic Layer (API/Rules) Persistence Layer (Database/Object Persistence/Model) I'm not advocating that they all be used...especially when you consider that too many layers/tiers could lead to an increase in complexity...I just wondered what the complete list might look like... Based on a couple of blogs I've found several different answers...and Javascript and client side technologies seem to have leaked in adding more client-side layers according to one blog the client side tier might even consist of Behavior Layer (Javascript, Flash) Presentation Layer (CSS/Images) Note: I though the entire client side layer was the presentation layer Structure Layer (XHTML, HTML) I'm just trying to get an abstract idea of what all the possible layers might be, (even though some people call them different things)

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  • Open XML SDK 2.0 - Split table to new power point slide when content flows off current slide

    - by amurra
    I have a bunch of data that I need to export from a website to a power point presentation and have been using Open XML SDK 2.0 to perform this task. I have a power point presentation that I am putting through Open XML SDK 2.0 Productivity Tool to generate the template code that I can use to recreate the export. On one of those slides I have a table and the requirement is to add data to that table and break that table across multiple slides if the table exceeds the bottom of the slide. The approach I have taken is to determine the height of the table and if it exceeds the height of the slide, move that new content into the next slide. I have read Bryan and Jones blog on adding repeating data to a power point slide, but my scenario is a little different. They use the following code: A.Table tbl = current.Slide.Descendants<A.Table>().First(); A.TableRow tr = new A.TableRow(); tr.Height = heightInEmu; tr.Append(CreateDrawingCell(imageRel + imageRelId)); tr.Append(CreateTextCell(category)); tr.Append(CreateTextCell(subcategory)); tr.Append(CreateTextCell(model)); tr.Append(CreateTextCell(price.ToString())); tbl.Append(tr); imageRelId++; This won't work for me since they know what height to set the table row to since it will be the height of the image, but when adding in different amounts of text I do not know the height ahead of time so I just set tr.Heightto a default value. Here is my attempt at figuring at the table height: A.Table tbl = tableSlide.Slide.Descendants<A.Table>().First(); A.TableRow tr = new A.TableRow(); tr.Height = 370840L; tr.Append(PowerPointUtilities.CreateTextCell("This"); tr.Append(PowerPointUtilities.CreateTextCell("is")); tr.Append(PowerPointUtilities.CreateTextCell("a")); tr.Append(PowerPointUtilities.CreateTextCell("test")); tr.Append(PowerPointUtilities.CreateTextCell("Test")); tbl.Append(tr); tableSlide.Slide.Save(); long tableHeight = PowerPointUtilities.TableHeight(tbl); Here are the helper methods: public static A.TableCell CreateTextCell(string text) { A.TableCell tableCell = new A.TableCell( new A.TextBody(new A.BodyProperties(), new A.Paragraph(new A.Run(new A.Text(text)))), new A.TableCellProperties()); return tableCell; } public static Int64Value TableHeight(A.Table table) { long height = 0; foreach (var row in table.Descendants<A.TableRow>() .Where(h => h.Height.HasValue)) { height += row.Height.Value; } return height; } This correctly adds the new table row to the existing table, but when I try and get the height of the table, it returns the original height and not the new height. The new height meaning the default height I initially set and not the height after a large amount of text has been inserted. It seems the height only gets readjusted when it is opened in power point. I have also tried accessing the height of the largest table cell in the row, but can't seem to find the right property to perform that task. My question is how do you determine the height of a dynamically added table row since it doesn't seem to update the height of the row until it is opened in power point? Any other ways to determine when to split content to another slide while using Open XML SDK 2.0? I'm open to any suggestion on a better approach someone might have taken since there isn't much documentation on this subject.

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  • Erlang OTP application design

    - by Toby Hede
    I am struggling a little coming to grips with the OTP development model as I convert some code into an OTP app. I am essentially making a web crawler and I just don't quite know where to put the code that does the actual work. I have a supervisor which starts my worker: -behaviour(supervisor). -define(CHILD(I, Type), {I, {I, start_link, []}, permanent, 5000, Type, [I]}). init(_Args) -> Children = [ ?CHILD(crawler, worker) ], RestartStrategy = {one_for_one, 0, 1}, {ok, {RestartStrategy, Children}}. In this design, the Crawler Worker is then responsible for doing the actual work: -behaviour(gen_server). start_link() -> gen_server:start_link(?MODULE, [], []). init([]) -> inets:start(), httpc:set_options([{verbose_mode,true}]), % gen_server:cast(?MODULE, crawl), % ok = do_crawl(), {ok, #state{}}. do_crawl() -> % crawl! ok. handle_cast(crawl}, State) -> ok = do_crawl(), {noreply, State}; do_crawl spawns a fairly large number of processes and requests that handle the work of crawling via http. Question, ultimately is: where should the actual crawl happen? As can be seen above I have been experimenting with different ways of triggering the actual work, but still missing some concept essential for grokering the way things fit together. Note: some of the OTP plumbing is left out for brevity - the plumbing is all there and the system all hangs together

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  • Alternatives to NServiceBus that doesn't use MSMQ

    - by G33kKahuna
    I think the title sums it all .... We have a .NET 2.0 system trying to implement a distributed pub/ sub model. I came across NServiceBus, RhinoBus and MassTransit. Unfortunately, these are MSMQ based. I am tasked to figure out pub/ sub alternatives that uses a different messaging alternatives ... the only reason for seeking MSMQ alternatives is to overcome the message size restriction. Since our enterprise app messages can potentially get truncated due to per message restriction... any guidance is much appreciated

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  • C#: Inheritance, Overriding, and Hiding

    - by Rosarch
    I'm having difficulty with an architectural decision for my C# XNA game. The basic entity in the world, such as a tree, zombie, or the player, is represented as a GameObject. Each GameObject is composed of at least a GameObjectController, GameObjectModel, and GameObjectView. These three are enough for simple entities, like inanimate trees or rocks. However, as I try to keep the functionality as factored out as possible, the inheritance begins to feel unwieldy. Syntactically, I'm not even sure how best to accomplish my goals. Here is the GameObjectController: public class GameObjectController { protected GameObjectModel model; protected GameObjectView view; public GameObjectController(GameObjectManager gameObjectManager) { this.gameObjectManager = gameObjectManager; model = new GameObjectModel(this); view = new GameObjectView(this); } public GameObjectManager GameObjectManager { get { return gameObjectManager; } } public virtual GameObjectView View { get { return view; } } public virtual GameObjectModel Model { get { return model; } } public virtual void Update(long tick) { } } I want to specify that each subclass of GameObjectController will have accessible at least a GameObjectView and GameObjectModel. If subclasses are fine using those classes, but perhaps are overriding for a more sophisticated Update() method, I don't want them to have to duplicate the code to produce those dependencies. So, the GameObjectController constructor sets those objects up. However, some objects do want to override the model and view. This is where the trouble comes in. Some objects need to fight, so they are CombatantGameObjects: public class CombatantGameObject : GameObjectController { protected new readonly CombatantGameModel model; public new virtual CombatantGameModel Model { get { return model; } } protected readonly CombatEngine combatEngine; public CombatantGameObject(GameObjectManager gameObjectManager, CombatEngine combatEngine) : base(gameObjectManager) { model = new CombatantGameModel(this); this.combatEngine = combatEngine; } public override void Update(long tick) { if (model.Health <= 0) { gameObjectManager.RemoveFromWorld(this); } base.Update(tick); } } Still pretty simple. Is my use of new to hide instance variables correct? Note that I'm assigning CombatantObjectController.model here, even though GameObjectController.Model was already set. And, combatants don't need any special view functionality, so they leave GameObjectController.View alone. Then I get down to the PlayerController, at which a bug is found. public class PlayerController : CombatantGameObject { private readonly IInputReader inputReader; private new readonly PlayerModel model; public new PlayerModel Model { get { return model; } } private float lastInventoryIndexAt; private float lastThrowAt; public PlayerController(GameObjectManager gameObjectManager, IInputReader inputReader, CombatEngine combatEngine) : base(gameObjectManager, combatEngine) { this.inputReader = inputReader; model = new PlayerModel(this); Model.Health = Constants.PLAYER_HEALTH; } public override void Update(long tick) { if (Model.Health <= 0) { gameObjectManager.RemoveFromWorld(this); for (int i = 0; i < 10; i++) { Debug.WriteLine("YOU DEAD SON!!!"); } return; } UpdateFromInput(tick); // .... } } The first time that this line is executed, I get a null reference exception: model.Body.ApplyImpulse(movementImpulse, model.Position); model.Position looks at model.Body, which is null. This is a function that initializes GameObjects before they are deployed into the world: public void Initialize(GameObjectController controller, IDictionary<string, string> data, WorldState worldState) { controller.View.read(data); controller.View.createSpriteAnimations(data, _assets); controller.Model.read(data); SetUpPhysics(controller, worldState, controller.Model.BoundingCircleRadius, Single.Parse(data["x"]), Single.Parse(data["y"]), bool.Parse(data["isBullet"])); } Every object is passed as a GameObjectController. Does that mean that if the object is really a PlayerController, controller.Model will refer to the base's GameObjectModel and not the PlayerController's overriden PlayerObjectModel? In response to rh: This means that now for a PlayerModel p, p.Model is not equivalent to ((CombatantGameObject)p).Model, and also not equivalent to ((GameObjectController)p).Model. That is exactly what I do not want. I want: PlayerController p; p.Model == ((CombatantGameObject)p).Model p.Model == ((GameObjectController)p).Model How can I do this? override?

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  • Squid handling of concurrent cache misses

    - by Oliver H-H
    We're using a Squid cache to off-load traffic from our web servers, ie. it's setup as a reverse-proxy responding to inbound requests before they hit our web servers. When we get blitzed with concurrent requests for the same request that's not in the cache, Squid proxies all the requests through to our web ("origin") servers. For us, this behavior isn't ideal: our origin servers gets bogged down trying to fulfill N identical requests concurrently. Instead, we'd like the first request to proxy through to the origin server, the rest of the requests to queue at the Squid layer, and then all be fulfilled by Squid when the origin server has responded to that first request. Does anyone know how to configure Squid to do this? We've read through the documentation multiple times and thoroughly web-searched the topic, but can't figure out how to do it. We use Akamai too and, interestingly, this is its default behavior. (However, Akamai has so many nodes that we still see lots of concurrent requests in certain traffic spike scenarios, even with Akamai's super-node feature enabled.) This behavior is clearly configurable for some other caches, eg. the Ehcache documentation offers the option "Concurrent Cache Misses: A cache miss will cause the filter chain, upstream of the caching filter to be processed. To avoid threads requesting the same key to do useless duplicate work, these threads block behind the first thread." Some folks call this behavior a "blocking cache," since the subsequent concurrent requests block behind the first request until it's fulfilled or timed-out. Thx for looking over my noob question! Oliver

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