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  • What is the best practice for accessing Model using MVVM pattern

    - by Dzenand
    I have a database that communicates with webservices with my Model (own thread) and exposes Data Objects. My UI application consists of different Views and ViewModels and Custom Controls. I'm using ServiceProvider (IServiceProvider) to access the Model and route the events to the UI thread. Communication between the ViewModels is handeled by a Messenger. Is this way to go? I was also wondering what is the best way to strucutre the DataObjects At the moment i have the DataObjects that have a hierarchy structure but does not support INotifyProperty though the children list are of type of ObservableCollection. I have no possiblity to implement notifypropertychange on the properties. I was wondering the best way of making them MVVM friendly. Implementing a partial class and adding all the properties or commands that are necessary or wrapping all the DataObjects and keep the Model list and MVVM list in sync. All thoughts and ideas are appreciated.

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  • return Queryable<T> or List<T> in a Repository<T>

    - by Danny Chen
    Currently I'm building an windows application using sqlite. In the data base there is a table say User, and in my code there is a Repository<User> and a UserManager. I think it's a very common design. In the repository there is a List method: //Repository<User> class public List<User> List(where, orderby, topN parameters and etc) { //query and return } This brings a problem, if I want to do something complex in UserManager.cs: //UserManager.cs public List<User> ListUsersWithBankAccounts() { var userRep = new UserRepository(); var bankRep = new BankAccountRepository(); var result = //do something complex, say "I want the users live in NY //and have at least two bank accounts in the system } You can see, returning List<User> brings performance issue, becuase the query is executed earlier than expected. Now I need to change it to something like a IQueryable<T>: //Repository<User> class public TableQuery<User> List(where, orderby, topN parameters and etc) { //query and return } TableQuery<T> is part of the sqlite driver, which is almost equals to IQueryable<T> in EF, which provides a query and won't execute it immediately. But now the problem is: in UserManager.cs, it doesn't know what is a TableQuery<T>, I need to add new reference and import namespaces like using SQLite.Query in the business layer project. It really brings bad code feeling. Why should my business layer know the details of the database? why should the business layer know what's SQLite? What's the correct design then?

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  • The one true domain model - a fallacy?

    - by James L
    I've just finished working for a client which has burnt millions on a project to come up with the 'one true domain model' for their business. This was the project's sole deliverable. What are your thoughts on this? Is a single version of the truth realistic?

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  • How to evaluate "enterprise" platforms?

    - by Ran Biron
    Hi all, I'm tasked with evaluating an "enterprise" platform for the next-gen version of a product. We're currently considering two "types" of platforms - RAD (workflow engine, integrated UI, small cores of "technology plugins" to the workflows, automatic persisting of state...) like SalesForce.com / Service-Now.com and "cloud based" (EC2 / AppEngine...). While I have a few ideas on where to start, I'd like your opinions - how would you evaluate platforms for an enterprise suite of products? What factors would you consider? How would you eliminate weak options quickly enough to be able to concentrate on the few strong ones? Also interesting is how would you compare enterprise RAD (proven technology, quick to develop - but tends to look "the same as the competition") to cloud-based technology (lots of "buzz", not that many competitors - easy to justify to management, but probably lacking (?) enterprise tools and experience). As said before - I have a few ideas, but would like to see some answers before I post mine so I wouldn't drive the discussion to a specific place. RB.

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  • Stored Procedure or calculations via IQueryable?

    - by Shawn Mclean
    This is a question that is based on choosing performance over design practices. If I have a method that will be executed many times a second; public static IQueryable<IPerson> InRadius(this IQueryable<IPerson> query, Coordinate center, double radius) { return (from u in query where CallHeavyMathFormula(u, center, radius) select u); } This extension method for IQueryable generates a SQL that does some heavy maths calculation (Cosine, Sine, etc). This would mean the application sends 1-2KB of sql to the server per call. I've heard of placing all application logic, in your application. I also would like to change to a database such as azure or one of those scalable databases in the future. How do I handle something like this? Should I leave it as it is now or write stored procedures? How do applications like twitter or facebook do it?

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  • The way cores, processes, and threads work exactly?

    - by unknownthreat
    I need a bit of an advice for understanding how this whole procedure work exactly. If I am incorrect in any part described below, please correct me. In a single core CPU, it runs each process in the OS, jumping around from one process to another to utilize the best of itself. A process can also have many threads, in which the CPU core runs through these threads when it is running on the respective process. Now, on a multiple core CPU, Do the cores run in every process together, or can the cores run separately in different processes at one particular point of time? For instance, you have program A running two threads, can a duo core CPU run both threads of this program? I think the answer should be yes if we are using something like OpenMP. But while the cores are running in this OpenMP-embedded process, can one of the core simply switch to other process? For programs that are created for single core, when running at 100%, why the CPU utilization of each core are distributed? (ex. A duo core CPU of 80% and 20%. The utilization percentage of all cores always add up to 100% for this case.) Do the cores try help each other run each thread of each process in some ways? Frankly, I'm not sure how this works exactly. Any advice is appreciated.

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  • How should I handle expected errors? eg. "username already exists"

    - by Pheter
    I am struggling to understand how I should design the error handling parts of my code. I recently asked a similar question about how I should go about returning server error codes to the user, eg. 404 errors. I learnt that I should handle the error from within the current part of the application; seem's simple enough. However, what should I do when I can't handle the error from the current link in the chain? For example, I may have a class that is used to manage authentication. One of it's methods could be createUser($username, $password). Within that function, I need to determine if the username already exists. If this is true, how should I alert the calling code about this? Returning null instead of a user object is one way. But how do I then know what caused the error? How should I handle errors in such a way that calling code can easily find out what caused the error? Is there a design pattern commonly used for this kind of situation?

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  • Localisable Resources: how can (should one?!) wrap a UI layer source as a BL layer service?

    - by Ciel
    A service that returns localised strings could be wrapped in a service, so that it could be used both locally (eg in an MVC app) and remotely (eg possibly Silverlight). But...if sticking with the standard practice of creating resources in the UI assembly, that would in effect make a lower layer (BL/Services) have to have a ref on a higher layer (UI)...a definite no-no. And whereas a lot of AppWide resources (eg: AppName, OK, Cancel, etc.) could be defined in a Common cross-cutting assembly, and the BL/ResourceSerouce could ref and wrap those, that doesn't work in a a Modular App, where the Core app should have no binding to/knowledge of any Module. One solution could be to have each module, once mounted in mem, 'register' their Resource files with the service, who would then return it to the service (rather a long round trip, but at least consistent as a service, and potentially resources/images could be shared with other resources). Secondly, that may work in a web app...but not sure how that pattern could be extended to a Silverlight modular app (the round tripping becomes prohibitive). ie...what are best practices for allowing Resources to be to be defined by the UI designer, in a higher level, but served from the lower BL layer, as a Service? Or is there a better way of understanding/solving the problem?

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  • MS SQL Server Job with precise timing

    - by TcKs
    Hi, I have a DB with game data (map, players, etc...) and I have a game core mechanics writen in T-SQL stored procedure. I need process game loop (via the stored procedure) every "X" seconds. I tried used the SQL Job, but when I set the interval to seconds, the SQL server stops responding. If I set the interval greater than one minute, all was ok. I need game loop precise in time, e.g. the game loop will run only once and will be executed every "X" precisely (tolerance should be less than one second). Can I do it with MS SQL Server capabilities? Or should I create a windows service which will repeatly execute game loop procedure? Or should I go another way? Thanks! EDIT: The game loop stored procedure takes less than the interval.

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  • Question about domain models & their visibility...

    - by Another SO User
    I was involved in an interesting debate about the visibility of domain models & was wondering if people here have any good guidance. Per my understanding of MDA, we need not expose the domain model throughout the application layers & tiers The reason being that any change to the domain model has an impact in the overall application The wise thing to do would be to expose light-weight object (DTO's) which are a small sub-set of the domain model to abstract the actual model On the flip side, any change to the domain model would mean changing various DTO's throughout the application for the change to be visible, while if we do expose the domain model, then the change is in a single location Hope to see some comments & thoughts about this. Appreciate all the help!

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  • Get an Entity in Save Method, What is correct form ?

    - by Felipe
    Hi everybody I'm begginer in asp.net mvc and i have some doubts. P.S: I'm using DDD to learn I have an ACtion in a Controller and it'll save an entity (from my model) by a repository (for a database). My doubts is, How can I get the informations from the View and save it by a repository in my Controller ? Is it correct to get an entity of my Model in Save method of controller, like this: public ActionResult Save(Product product) { // validate object // save data in repository return View("Success"); } Or Need I get an DTO (with a structure similar to my entity) and create an object passing property by property to an entity ? I didnt' like of FormCollection and I'd like to know, What is recommended architecturally ? Thanks a lot guys Cheers

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  • Reusing of a PreparedStatement between methods?

    - by MRalwasser
    We all know that we should rather reuse a JDBC PreparedStatement than creating a new instance within a loop. But how to deal with PreparedStatement reuse between different method invocations? Does the reuse-"rule" still count? Should I really consider using a field for the PreparedStatement or should I close and re-create the prepared statement in every invocation? (Of course an instance of such a class would be bound to a Connection which might be a disadvantage) I am aware that the ideal answer might be "it depends". But I am looking for a best practice for less experienced developers that they will do the right choice in most of the cases.

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  • Real life Java Swing Project

    - by santiagobasulto
    Hi everybody! I've been working with swing for the last 2 years, but i'm still not satisfy with my own work. The apps are "fast" enough, but the development isn't enough "clean". Can you recommend me any real world project, book, or something similar that shows me how a real world swing app work. May be a framework, something structured, etc. For example, i'm thinking i may code a "window manager" that has all the window of the app in an unified resource, may be cached, etc. I think all those good ideas must be implemented already. Thanks!

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  • Application that depends heavily on stored procedures

    - by PieterG
    We currently have an application that depends largely on stored procedures. There is a heavy use of temp tables. It's an extremely large application. Facing this situation, I would like to use Entity Framework or Linq2Sql for a rewrite. I might consider using Fluent Hibernate or Subsonic, as i've used them quite extensively in the past. I've had problems with Linq2Sql generating the return types for the stored procedures because of the usage of the temp tables, and I think it's cumbersome to go and change all the stored procedures from temp tables to in-memory tables. Considering the 2 choices that I want to make, which one of the 2 is the best route to go and why? If my choices are extremely idiotic, please provide alternatives. Edit: The reason for the question and the change is that the data access layer is non-existent and was built 10 years ago. We currently still run into a lot of issues with it. I don't want to divulge too much, but if you saw it, your eyes would start bleeding :)

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  • How can I build a voting system to support multiple types of objects to vote on?

    - by Kyle Hayes
    I'm really looking for something very similar to the way SO is setup where a few different kinds of things can be voted on (questions AND answers). What kind of DB schema, generally, could I use to support voting on many different kinds of objects? Would I have a single Vote table that would have references to other objects in the database? Or do I have to have or should have a separate vote table for each of the objects I would like to vote on.

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  • How is fseek() implemented in the filesystem?

    - by pajton
    This is not a pure programming question, however it impacts the performance of programs using fseek(), hence it is important to know how it works. A little disclaimer so that it doesn't get closed. I am wondering how efficient it is to insert data in the middle of the file. Supposing I have a file with 1MB data and then I insert something at the 512KB offset. How efficient would that be compared to appending my data at the end of the file? Just to make the example complete lets say I want to insert 16KB of data. I understand the answer varies depending on the filesystem, however I assume that the techniques used in common filesystems are quite similar and I just want to get the right notion of it.

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  • What is the cost of object creating.

    - by Tony
    Hi If I have to choose between static method and creating an instance and use instance method, I will choose static methods always. but what is the detailed overhead of creating an instance? for example I saw a DAL which can be done with static classes but they choose to make it instance now in the BLL at every single call they call something like. new Customer().GetData(); how far this can be bad? Thanks

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  • ASP.NET Website or Web service?

    - by fireBand
    Hi, I am trying to implement a service to download a image file. The code does nothing but upload a file to the response with each client request. There are no SOAP messages involved but I am planning to implement it as ASP.NET web service. It can also be implement as ASP.NET website but since it has no view (forms, html etc) I planned to implement a web-service. Is this a better approach? Does ASP.NET Website offer better performance that a Web-service? Which one would be better is this situation? Thanks in advance.

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  • ASP.NET MVC image upload store location (db vs filesystem)

    - by adrin
    I am writing web application using ASP.NET MVC + NHibernate + Postres stack. I wonder if images uploaded should be stored in database as binary blobs or on filesystem (and reference only in db). One advantage of db storage I can think of is easy backup/recovery of all data without reverting to filesystem copy tools. On the other hand I suspect that filesystem access may be faster (but is it especially when dealing with many concurrent requests?) What are your suggestions?

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  • Are there any frameworks for data subscription and update?

    - by Timothy Pratley
    There is one server with multiple clients. The clients are viewing subsets of the servers entire data. If the data that a client is viewing changes, the client should be informed of the changes so that it displays the current data. Example: Two clients are viewing a list of users in an administration screen. One client adds a new user to the list and modifies the permissions of another user. The other client sees the changes propagated to their view.

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