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  • How to mimic built-in .NET serialization idioms?

    - by Matt Enright
    I have a library (written in C#) for which I need to read/write representations of my objects to disk (or to any Stream) in a particular binary format (to ensure compatibility with C/Java library implementations). The format requires a fair amount of bit-packing and some DEFLATE'd bytestreams. I would like my library, however, to be as idiomatic .NET as possible, however, and so would like to provide an API as close as possible to the normal binary serialization process. I'm aware of the ability to implement the IFormatter interface, but being that I really am unable to reuse any part of the built-in serialization stack, is it worth doing this, or will it just bring unnecessary overhead. In other words: Implement IFormatter and co. OR Just provide "Serialize"/"Deserialize" methods that act on a Stream? A good point brought up below about needing the serialization semantics for any case involving Remoting. In a case where using MarshalByRef objects is feasible, I'm pretty sure that this won't be an issue, so leaving that aside are there any benefits or drawbacks to using the ISerializable/IFormatter versus a custom stack (or, is my understanding remoting incorrectly)?

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  • ASP.NET MVC PartialView generic ModelView

    - by Greg Ogle
    I have an ASP.NET MVC application which I want to dynamically pick the partial view and what data gets passed to it, while maintaining strong types. So, in the main form, I want a class that has a view model that contains a generically typed property which should contain the data for the partial view's view model. public class MainViewModel<T> { public T PartialViewsViewModel { get; set; } } In the User Control, I would like something like: Inherits="System.Web.Mvc.ViewUserControl<MainViewModel<ParticularViewModel>>" %> Though in my parent form, I must put Inherits="System.Web.Mvc.ViewPage<MainViewModel<ParticularViewModel>>" %> for it to work. Is there a way to work around this? The use case is to make the user control pluggable. I understand that I could inherit a base class, but that would put me back to having something like a dictionary instead of a typed view model.

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  • Unit of Work Pattern in .Net

    - by Jazza
    Does anyone have any concrete examples of a simple Unit of Work pattern in C# or Visual Basic that would handle the following scenario? I'm writing a WinForms application in which a customer can have multiple addresses associated with it. The user can add, edit and delete addresses belonging to the customer before the customer is saved back to the database. Therefore, at the time of saving, all the original addresses need to be deleted from the database and the new addresses added in a single transaction.

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  • What is your custom exception hierrarchy?

    - by bonefisher
    My question is: how would you create exception hierarchy in your application? Designing the architecture of an application, from my perspective, we could have three types of exceptions: the built-in (e.g.: InvalidOperationException) custom internal system faults (DB transaction failed on commit, DbTransactionFailedException) custom business exceptions (BusinessRuleViolationException) Class hierarchy: Exception MyAppInternalException DbTransactionFailedException MyServerTimeoutException ... MyAppBusinessRuleViolationException UsernameAlreadyExistsException ... where only MyAppInternalException & MyAppBusinessRuleViolationException would be catched.

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  • Best way to handle multiple getView calls from inside an Adapter

    - by Samuh
    I have a ListView with custom ArrayAdapter. Each of the row in this ListView has an icon and some text. These icons are downloaded in background,cached and then using a callback, substituted in their respective ImageViews. The logic to get a thumbnail from cache or download is triggered every time getView() runs. Now, according to Romain Guy: "there is absolutely no guarantee on the order in which getView() will be called nor how many times." I have seen this happen, for a row of size two getView() was being called six times! How do I change my code to avoid duplicate thumbnail-fetch-requests and also handle view recycling? Thanks.

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  • Representing game states in Tic Tac Toe

    - by dacman
    The goal of the assignment that I'm currently working on for my Data Structures class is to create a of Quantum Tic Tac Toe with an AI that plays to win. Currently, I'm having a bit of trouble finding the most efficient way to represent states. Overview of current Structure: AbstractGame Has and manages AbstractPlayers (game.nextPlayer() returns next player by int ID) Has and intializes AbstractBoard at the beginning of the game Has a GameTree (Complete if called in initialization, incomplete otherwise) AbstractBoard Has a State, a Dimension, and a Parent Game Is a mediator between Player and State, (Translates States from collections of rows to a Point representation Is a StateConsumer AbstractPlayer Is a State Producer Has a ConcreteEvaluationStrategy to evaluate the current board StateTransveralPool Precomputes possible transversals of "3-states". Stores them in a HashMap, where the Set contains nextStates for a given "3-state" State Contains 3 Sets -- a Set of X-Moves, O-Moves, and the Board Each Integer in the set is a Row. These Integer values can be used to get the next row-state from the StateTransversalPool SO, the principle is Each row can be represented by the binary numbers 000-111, where 0 implies an open space and 1 implies a closed space. So, for an incomplete TTT board: From the Set<Integer> board perspective: X_X R1 might be: 101 OO_ R2 might be: 110 X_X R3 might be: 101, where 1 is an open space, and 0 is a closed space From the Set<Integer> xMoves perspective: X_X R1 might be: 101 OO_ R2 might be: 000 X_X R3 might be: 101, where 1 is an X and 0 is not From the Set<Integer> oMoves perspective: X_X R1 might be: 000 OO_ R2 might be: 110 X_X R3 might be: 000, where 1 is an O and 0 is not Then we see that x{R1,R2,R3} & o{R1,R2,R3} = board{R1,R2,R3} The problem is quickly generating next states for the GameTree. If I have player Max (x) with board{R1,R2,R3}, then getting the next row-states for R1, R2, and R3 is simple.. Set<Integer> R1nextStates = StateTransversalPool.get(R1); The problem is that I have to combine each one of those states with R1 and R2. Is there a better data structure besides Set that I could use? Is there a more efficient approach in general? I've also found Point<-State mediation cumbersome. Is there another approach that I could try there? Thanks! Here is the code for my ConcretePlayer class. It might help explain how players produce new states via moves, using the StateProducer (which might need to become StateFactory or StateBuilder). public class ConcretePlayerGeneric extends AbstractPlayer { @Override public BinaryState makeMove() { // Given a move and the current state, produce a new state Point playerMove = super.strategy.evaluate(this); BinaryState currentState = super.getInGame().getBoard().getState(); return StateProducer.getState(this, playerMove, currentState); } } EDIT: I'm starting with normal TTT and moving to Quantum TTT. Given the framework, it should be as simple as creating several new Concrete classes and tweaking some things.

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  • ViewModel updates after Model server roundtrip

    - by Pavel Savara
    I have stateless services and anemic domain objects on server side. Model between server and client is POCO DTO. The client should become MVVM. The model could be graph of about 100 instances of 20 different classes. The client editor contains diverse tab-pages all of them live-connected to model/viewmodel. My problem is how to propagate changes after server round-trip nice way. It's quite easy to propagate changes from ViewModel to DTO. For way back it would be possible to throw away old DTO and replace it whole with new one, but it will cause lot of redrawing for lists/DataTemplates. I could gather the server side changes and transmit them to client side. But the names of fields changed would be domain/DTO specific, not ViewModel specific. And the mapping seems nontrivial to me. If I should do it imperative way after round-trip, it would break SOC/modularity of viewModels. I'm thinking about some kind of mapping rule engine, something like automappper or emit mapper. But it solves just very plain use-cases. I don't see how it would map/propagate/convert adding items to list or removal. How to identify instances in collections so it could merge values to existing instances. As well it should propagate validation/error info. Maybe I should implement INotifyPropertyChanged on DTO and try to replay server side events on it ? And then bind ViewModel to it ? Would binding solve the problems with collection merges nice way ? Is EventAgregator from PRISM useful for that ? Is there any event record-replay component ? Is there better client side pattern for architecture with server side logic ?

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  • What is your strategy to avoid dynamic typing errors in Python (NoneType has not attribute x)?

    - by Koen Bok
    Python is one of my favorite languages, but I really have a love/hate relationship with it's dynamicness. Apart from the advantages, it often results in me forgetting to check a type, trying to call an attribute and getting the NoneType (or any other) has no attribute x error. A lot of them are pretty harmless but if not handled correctly they can bring down your entire app/process/etc. Over time I got better predicting where these could pop up and adding explicit type checking, but because I'm only human I miss one occasionally and then some end-user finds it. So I'm interested in your strategy to avoid these. Do you use type-checking decorators? Maybe special object wrappers? Please share...

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  • How to avoid using this in a constructor

    - by Paralife
    I have this situation: interface MessageListener { void onMessageReceipt(Message message); } class MessageReceiver { MessageListener listener; public MessageReceiver(MessageListener listener, other arguments...) { this.listener = listener; } loop() { Message message = nextMessage(); listener.onMessageReceipt(message); } } and I want to avoid the following pattern: (Using the this in the Client constructor) class Client implements MessageListener { MessageReceiver receiver; MessageSender sender; public Client(...) { receiver = new MessageReceiver(this, other arguments...); sender = new Sender(...); } . . . @Override public void onMessageReceipt(Message message) { if(Message.isGood()) sender.send("Congrtulations"); else sender.send("Boooooooo"); } } The reason why i need the above functionality is because i want to call the sender inside the onMessageReceipt() function, for example to send a reply. But I dont want to pass the sender into a listener, so the only way I can think of is containing the sender in a class that implements the listener, hence the above resulting Client implementation. Is there a way to achive this without the use of 'this' in the constructor? It feels bizare and i dont like it, since i am passing myself to an object(MessageReceiver) before I am fully constructed. On the other hand, the MessageReceiver is not passed from outside, it is constructed inside, but does this 'purifies' the bizarre pattern? I am seeking for an alternative or an assurance of some kind that this is safe, or situations on which it might backfire on me.

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  • Revision histories and documenting changes

    - by jasonline
    I work on legacy systems and I used to see revision history of files or functions being modified every release in the source code, for example: // // Rev. No Date Author Description // ------------------------------------------------------- // 1.0 2009/12/01 johnc <Some description> // 1.1 2009/12/24 daveb <Some description> // ------------------------------------------------------- void Logger::initialize() { // a = b; // Old code, just commented and not deleted a = b + c; // New code } I'm just wondering if this way of documenting history is still being practiced by many today? If yes, how do you apply modifications on the source code - do you comment it or delete it completely? If not, what's the best way to document these revisions? If you use version control systems, does it follow that your source files contain pure source codes, except for comments when necessary (no revision history for each function, etc.)?

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  • What is the best way to handle validity dates in applications ?

    - by user214626
    Hello, How do we model these objects ? Scenario 1: Price changes in a time period EffectiveDate ExpiryDate Price 2009-01-01 2009-01-31 800$ 2009-02-01 Null 900$ So, if the price changes to 910$ on 2009-02-15, then the system should automatically update the expiry date on the previous effective price to 2009-02-14, to keep it consistent. Scenario 2: No price specified between 2009-02-01 to 2009-02-28 EffectiveDate ExpiryDate Price 2009-01-01 2009-01-31 800$ 2009-03-01 Null 900$ So, if new price is specified for 2009-02-15 onwards , then the system should automatically set the expiry date on the record to be inserted to 2009-02-28, because already a record effective from 2009-03-01 exists. Please suggest an effective way to handle these scenarios to model my framework, or are there any frameworks around that can do this . Thanks

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  • Newbie T-SQL dynamic stored procedure -- how can I improve it?

    - by Andy Jones
    I'm new to T-SQL; all my experience is in a completely different database environment (Openedge). I've learned enough to write the procedure below -- but also enough to know that I don't know enough! This routine will have to go into a live environment soon, and it works, but I'm quite certain there are a number of c**k-ups and gotchas in it that I know nothing about. The routine copies data from table A to table B, replacing the data in table B. The tables could be in any database. I plan to call this routine multiple times from another stored procedure. Permissions aren't a problem: the routine will be run by the dba as a timed job. Could I have your suggestions as to how to make it fit best-practice? To bullet-proof it? ALTER PROCEDURE [dbo].[copyTable2Table] @sdb varchar(30), @stable varchar(30), @tdb varchar(30), @ttable varchar(30), @raiseerror bit = 1, @debug bit = 0 as begin set nocount on declare @source varchar(65) declare @target varchar(65) declare @dropstmt varchar(100) declare @insstmt varchar(100) declare @ErrMsg nvarchar(4000) declare @ErrSeverity int set @source = '[' + @sdb + '].[dbo].[' + @stable + ']' set @target = '[' + @tdb + '].[dbo].[' + @ttable + ']' set @dropStmt = 'drop table ' + @target set @insStmt = 'select * into ' + @target + ' from ' + @source set @errMsg = '' set @errSeverity = 0 if @debug = 1 print('Drop:' + @dropStmt + ' Insert:' + @insStmt) -- drop the target table, copy the source table to the target begin try begin transaction exec(@dropStmt) exec(@insStmt) commit end try begin catch if @@trancount > 0 rollback select @errMsg = error_message(), @errSeverity = error_severity() end catch -- update the log table insert into HHG_system.dbo.copyaudit (copytime, copyuser, source, target, errmsg, errseverity) values( getdate(), user_name(user_id()), @source, @target, @errMsg, @errSeverity) if @debug = 1 print ( 'Message:' + @errMsg + ' Severity:' + convert(Char, @errSeverity) ) -- handle errors, return value if @errMsg <> '' begin if @raiseError = 1 raiserror(@errMsg, @errSeverity, 1) return 1 end return 0 END Thanks!

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  • Exception design: Custom exceptions reading data from file?

    - by User
    I have a method that reads data from a comma separated text file and constructs a list of entity objects, let's say customers. So it reads for example, Name Age Weight Then I take these data objects and pass them to a business layer that saves them to a database. Now the data in this file might be invalid, so I'm trying to figure out the best error handling design. For example, the text file might have character data in the Age field. Now my question is, should I throw an exception such as InvalidAgeException from the method reading the file data? And suppose there is length restriction on the Name field, so if the length is greater than max characters do I throw a NameTooLongException or just an InvalidNameException, or do I just accept it and wait until the business layer gets a hold of it and throw exceptions from there? (If you can point me to a good resource that would be good too)

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  • Which Code Should Go Where in MVC Structure

    - by Oguz
    My problem is in somewhere between model and controller.Everything works perfect for me when I use MVC just for crud (create, read, update, delete).I have separate models for each database table .I access these models from controller , to crud them . For example , in contacts application,I have actions (create, read, update, delete) in controller(contact) to use model's (contact) methods (create, read, update, delete). The problem starts when I try to do something more complicated. There are some complex processes which I do not know where should I put them. For example , in registering user process. I can not just finish this process in user model because , I have to use other models too (sending mails , creating other records for user via other models) and do lots of complex validations via other models. For example , in some complex searching processes , I have to access lots of models (articles, videos, images etc.) Or, sometimes , I have to use apis to decide what I will do next or which database model I will use to record data So where is the place to do this complicated processes. I do not want to do them in controllers , Because sometimes I should use these processes in other controllers too. And I do not want to put these process in models because , I use models as database access layers .May be I am wrong,I want to know . Thank you for your answer .

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  • How Can I Find Out *HOW* My Site Was Hacked? How Do I Find Site Vulnerabilities?

    - by Imageree
    One of my custom developed ASP.NET sites was hacked today: "Hacked By Swan (Please Stop Wars !.. )" It is using ASP.NET and SQL Server 2005 and IIS 6.0 and Windows 2003 server. I am not using Ajax and I think I am using stored procedures everywhere I am connecting to the database so I dont think it is SQL injection. I have now removed the write permission on the folders. How can I find out what they did to hack the site and what to do to prevent it from happening again? The server is up to date with all Windows updates. What they have done is uploading 6 files (index.asp, index.html, index.htm,...) to the main directory for the website. What log files should I upload? I have log files for IIS from this folder: c:\winnt\system32\LogFiles\W3SVC1. I am willing to show it to some of you but don't think it is good to post on the Internet. Anyone willing to take a look at it? I have already searched on Google but the only thing I find there are other sites that have been hacked - I haven't been able to see any discussion about it. I know this is not strictly related to programming but this is still an important thing for programmers and a lot of programmers have been hacked like this.

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  • Only perform jquery effects/operations on certain pages

    - by Galen
    Up until now i've been dropping all my jquery code right inside the document.ready function. I'm thinking that for certain situations this isnt the best way to go. for example: If i want an animation to perform when a certain page loads what is the best way to go about that. $(document).ready(function() { $("#element_1").fadeIn(); $("#element_2").delay('100').fadeIn(); $("#element_3").delay('200').fadeIn(); }); If this is right inside of document.ready then every time ANY page loads it's going to check each line and look for that element. What is the best way to tell jquery to only perform a chunk of code on a certain page to avoid this issue.

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  • Downloading RSS using python

    - by Vojtech R.
    Hi, I have list of 200 rss feeds, which I have to downloading. It's continuous process - I have to download every post, nothing can be missing, but also no duplicates. So best practice should be remember last update of feed and control it for change in x-hour interval? And how to handle if downloader will be restarted? So downloader should remember, what were downloaded and dont download it again... It's somewhere implemented yet? Or any tips for article? Thanks

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  • Separation of concerns and authentication

    - by Tom Gilder
    I'm trying to be a Good Developer and separate my concerns out. I've got an ASP.NET MVC project with all my web code, and a DAL project with all the model code. Sometimes code in the DAL needs to check if the current user is authorized to perform some actions, by checking something like CurrentUser.IsAdmin. For the web site, the current is derived from the Windows username (from HttpContext.Current.User.Identity), but this is clearly a web concern and shouldn't be coupled to the DAL. What's the best pattern to loosely couple the authentication? Should the DAL be asking the MVC code for a username, or the MVC be telling the DAL? Are there advantages or disadvantages to one or the other? Thank you!

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  • What would you like to correct and/or improve in this java implementation of Chain Of Responsibility

    - by Maciek Kreft
    package design.pattern.behavioral; import design.pattern.behavioral.ChainOfResponsibility.*; public class ChainOfResponsibility { public static class Chain { private Request[] requests = null; private Handler[] handlers = null; public Chain(Handler[] handlers, Request[] requests){ this.handlers = handlers; this.requests = requests; } public void start() { for(Request r : requests) for (Handler h : handlers) if(h.handle(r)) break; } } public static class Request { private int value; public Request setValue(int value){ this.value = value; return this; } public int getValue() { return value; } } public static class Handler<T1> { private Lambda<T1> lambda = null; private Lambda<T1> command = null; public Handler(Lambda<T1> condition, Lambda<T1> command) { this.lambda = condition; this.command = command; } public boolean handle(T1 request) { if (lambda.lambda(request)) command.lambda(request); return lambda.lambda(request); } } public static abstract class Lambda<T1>{ public abstract Boolean lambda(T1 request); } } class TestChainOfResponsibility { public static void main(String[] args) { new TestChainOfResponsibility().test(); } private void test() { new Chain(new Handler[]{ // chain of responsibility new Handler<Request>( new Lambda<Request>(){ // command public Boolean lambda(Request condition) { return condition.getValue() >= 600; } }, new Lambda<Request>(){ public Boolean lambda(Request command) { System.out.println("You are rich: " + command.getValue() + " (id: " + command.hashCode() + ")"); return true; } } ), new Handler<Request>( new Lambda<Request>(){ public Boolean lambda(Request condition) { return condition.getValue() >= 100; } }, new Lambda<Request>(){ public Boolean lambda(Request command) { System.out.println("You are poor: " + command.getValue() + " (id: " + command.hashCode() + ")"); return true; } } ), }, new Request[]{ new Request().setValue(600), // chaining method new Request().setValue(100), } ).start(); } }

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  • Java Date vs Calendar

    - by Marty Pitt
    Could someone please advise the current "best practice" around Date and Calendar types. When writing new code, is it best to always favour Calendar over Date, or are there circumstances where Date is the more appropriate datatype?

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  • Is there a way of using one method to handle others to avoid code duplication?

    - by Artur
    I wonder if there is a way of writing a method or a class that would add to any method some code that is shared between many methods. The methods return different things and some of them are just void. Below is a part of the code that is duplicated in the methods. StartTimer(MethodBase.GetCurrentMethod().Name); try { // Actual method body } catch (Exception ex) { bool rethrow = ExceptionPolicy.HandleException(ex, "DALPolicy"); if (rethrow) { throw; } } finally { StopTimer(MethodBase.GetCurrentMethod().Name); } Any help would be greatly appreciated.

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