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  • Java : Singleton class instances in a Web based Application

    - by Preethi Jain
    I have this Singleton class inside a Web Application . public class MyDAO { private static MyDAO instance; private MyDAO() { } public static MyDAO getInstance() { if (instance == null) { instance = new MyDAO(); } return instance; } I will access it this way public void get_Data() { MyDAO dao = MyDAO.getInstance(); } How many Objects of MyDAO class will be created if there are 3 Users accessing the Application ?? Will there be one instance of MyDAO per User ??

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  • How can I get a string[] of all different values of a list?

    - by iTayb
    I have a class that has an list<Book> in it, and those Book objects has many many properties. string Subject is one of those properties. I'd like to get an string[] type value that will include all different subjects from all over the list. Is there an elegant way to do it, or I'll have to scan the whole list and enter each subject to it, then remove duplicates?

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  • Which is the "best" data access framework/approach for C# and .NET?

    - by Frans
    (EDIT: I made it a community wiki as it is more suited to a collaborative format.) There are a plethora of ways to access SQL Server and other databases from .NET. All have their pros and cons and it will never be a simple question of which is "best" - the answer will always be "it depends". However, I am looking for a comparison at a high level of the different approaches and frameworks in the context of different levels of systems. For example, I would imagine that for a quick-and-dirty Web 2.0 application the answer would be very different from an in-house Enterprise-level CRUD application. I am aware that there are numerous questions on Stack Overflow dealing with subsets of this question, but I think it would be useful to try to build a summary comparison. I will endeavour to update the question with corrections and clarifications as we go. So far, this is my understanding at a high level - but I am sure it is wrong... I am primarily focusing on the Microsoft approaches to keep this focused. ADO.NET Entity Framework Database agnostic Good because it allows swapping backends in and out Bad because it can hit performance and database vendors are not too happy about it Seems to be MS's preferred route for the future Complicated to learn (though, see 267357) It is accessed through LINQ to Entities so provides ORM, thus allowing abstraction in your code LINQ to SQL Uncertain future (see Is LINQ to SQL truly dead?) Easy to learn (?) Only works with MS SQL Server See also Pros and cons of LINQ "Standard" ADO.NET No ORM No abstraction so you are back to "roll your own" and play with dynamically generated SQL Direct access, allows potentially better performance This ties in to the age-old debate of whether to focus on objects or relational data, to which the answer of course is "it depends on where the bulk of the work is" and since that is an unanswerable question hopefully we don't have to go in to that too much. IMHO, if your application is primarily manipulating large amounts of data, it does not make sense to abstract it too much into objects in the front-end code, you are better off using stored procedures and dynamic SQL to do as much of the work as possible on the back-end. Whereas, if you primarily have user interaction which causes database interaction at the level of tens or hundreds of rows then ORM makes complete sense. So, I guess my argument for good old-fashioned ADO.NET would be in the case where you manipulate and modify large datasets, in which case you will benefit from the direct access to the backend. Another case, of course, is where you have to access a legacy database that is already guarded by stored procedures. ASP.NET Data Source Controls Are these something altogether different or just a layer over standard ADO.NET? - Would you really use these if you had a DAL or if you implemented LINQ or Entities? NHibernate Seems to be a very powerful and powerful ORM? Open source Some other relevant links; NHibernate or LINQ to SQL Entity Framework vs LINQ to SQL

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  • Cross-platform editing for LaTeX documents?

    - by pufferfish
    What solutions are there for working on a LaTeX document on both Windows and Linux? It's a large document, and I will be working daily on both platforms so compatibility is essential if it's two different pieces of software. Bonus points for a solution that includes easy previewing.

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  • Sorting a List based on an ArrayList within a custom Object

    - by Matt Weldon
    I am using a list to keep track of a number of custom Row objects as follows: Public Rows As List(Of Row)() Row has 2 properties, Key (a String) and Cells (an ArrayList). I need to be able to sort each Row within Rows based on a developer defined index of the Cells ArrayList. So for example based on the following Rows Row1.Cells = ("b", "12") Row2.Cells = ("a", "23") Rows.Sort(0) would result in Row2 being first in the Rows list. What would be the best way of going about implementing this? Thanks

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  • doublebuffering not reducing the flicker

    - by fishhead
    I am drawing an grid-work of objects in a Panel. when I scroll the the panel quickly I get a flicker. I thought that enabling the double buffering may take care of this but what I find is that it does not completely draw everything and I am left with blank sections. could anyone give me suggestions as to what may be happening and how I might correct it. UPDATE: I found that I was creating the graphics object with Creategraphics() rather than using the Parameter in the paint method

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  • Execution plan issue requires reset on SQL Server 2005, how to determine cause?

    - by Tony Brandner
    We have a web application that delivers training to thousands of corporate students running on top of SQL Server 2005. Recently, we started seeing that a single specific query in the application went from 1 second to about 30 seconds in terms of execution time. The application started throwing timeouts in that area. Our first thought was that we may have incorrect indexes, so we reviewed the tables and indexes. However, similar queries elsewhere in the application also run quickly. Reviewing the indexes showed us that they were configured as expected. We were able to narrow it down to a single query, not a stored procedure. Running this query in SQL Studio also runs quickly. We tried running the application in a different server environment. So a different web server with the same query, parameters and database. The query still ran slow. The query is a fairly large one related to determining a student's current list of training. It includes joins and left joins on a dozen tables and subqueries. A few of the tables are fairly large (hundreds of thousands of rows) and some of the other tables are small lookup tables. The query uses a grouping clause and a few where conditions. A few of the tables are quite active and the contents change often but the volume of added rows doesn't seem extreme. These symptoms led us to consider the execution plan. First off, as soon as we reset the execution plan cache with the SQL command 'DBCC FREEPROCCACHE', the problem went away. Unfortunately, the problem started to reoccur within a few days. The problem has continued to plague us for awhile now. It's usually the same query, but we did appear to see the problem occur in another single query recently. It happens enough to be a nuisance. We're having a heck of a time trying to fix it since we can't reproduce it in any other environment other than production. I have downloaded the High Availability guide from Red Gate and I read up more on execution plans. I hope to run the profiler on the live server, but I'm a bit concerned about impact. I would like to ask - what is the best way to figure out what is triggering this problem? Has anyone else seen this same issue?

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  • Is String.concat slower than Array approach to join strings

    - by Rajat
    Strings in JavaScript are immutable. Across the web and here on Stack Overflow as well, I came across the Array approach to concatenate strings: var a = []; a.push(arg1,arg,2....); console.log(a.join('')); I know that this approach is better than the simple console.log(arg1 + arg2 +.....); for reasons of skipping creating intermediate objects but how does it fair better against : arg1.concat(arg2,arg3.....);

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  • Model Binding with Parent/Child Relationship

    - by user296297
    I'm sure this has been answered before, but I've spent the last three hours looking for an acceptable solution and have been unable to find anything, so I apologize for what I'm sure is a repeat. I have two domain objects, Player and Position. Player's have a Position. My domain objects are POCOs tied to my database with NHibernate. I have an Add action that takes a Player, so I'm using the built in model binding. On my view I have a drop down list that lets a user select the Position for the Player. The value of the drop down list is the Id of the position. Everything gets populated correctly except that my Position object fails validation (ModelState.IsValid) because at the point of model binding it only has an Id and none of it's other required attributes. What is the preferred solution for solving this with ASP.NET MVC 2? Solutions I've tried... Fetch the Position from the database based on the Id before ModelState.IsValid is called in the Add action of my controller. I can't get the model to run the validation again, so ModelState.IsValid always returns false. Create a custom ModelBinder that inherits from the default binder and fetch the Position from the database after the base binder is called. The ModelBinder seems to be doing the validation so if I use anything from the default binder I'm hosed. Which means I have to completely roll my own binder and grab every value from the form...this seems really wrong and inefficient for such a common use-case. Solutions I think might work, I just can't figure out how to do... Turn off the validation for the Position class when used in Player. Write a custom ModelBinder leverages the default binder for most of the property binding, but lets me get the Position from the database BEFORE the default binder runs validation. So, how do the rest of you solve this? Thanks, Dan P.S. In my opinion having a PositionId on Player just for this case is not a good solution. There has to be solvable in a more elegant fashion.

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  • Decide which caching startegy to use ?

    - by hib
    Hi all, I want to cache my loaded data so that I can reduce my application start time . I know several strategies to store application data i.e. core data, nsuserdefaults , archiving . Now my scenario is that suppose that I have array of maximum 10 objects each object having 5 fields . So I can not decide which strategy to store this array an later retrieving the same . Thanks .

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  • aggregate over several variables in r

    - by Misha
    Dear overflowers, I have a rather large dataset in a long format where I need to count the number of instances of the ID due to two different variables, A & B. E.g. The same person can be represented in multiple rows due to either A or B. What I need to do is to count the number of instances of ID which is not too hard, but also count the number of ID due to A and B and return these as variables in the dataset. Regards, //Mi

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  • A quick way to map unordered list of longs to buffer location ?

    - by alhazen
    I have a large number of points (indexed by long) that are processed by multiple threads and I'm using a buffer to hold the output results in order. As the number of points processed is huge, what would be an efficient way to map the indexes of the points to the corresponding ordered position in the buffer ? Example: long bufferIndex bufferIndex index (if BufferSize = 2) (if BufferSize = 4) ---------------------------------------------- 2938 0 0 2939 1 1 2941 1 3 2940 0 2 Thanks.

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  • facebook photo album grouping photos in news feed

    - by John Klingelhoets
    We have a social media "platform" - when we schedule photos to be published to Facebook, if a user schedules photos - they all go into the same album, as they schedule photos throughout the day - the photos become grouped and do not appear as a large photo - but rather a bunch of photos in a album. Is there any way to prevent photos from being grouped in the new feed and it just showing the newest uploaded photo in stream? I do not see an option.

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  • String literals in python

    - by kjakeb
    Hello, Is there a way to declare a string variable in python such that everything inside of it is automatically escaped, or has its literal character value? I'm NOT asking how to escape the quotes with slashes, that's obvious. What I'm asking for is a general purpose way for making EVERYTHING in a string literal so that I don't have to manually go through and escape everything for very large strings. Anyone know of a solution? Thanks!

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  • Using xml to feed a silverlight application

    - by Aidenn
    Hey! I am building a Silverlight application that should get it's elements from XML defined objects, but I am kinda stuck: how should I feed the Silverlight application with the data in the XML? What would be a good approach? Can this be done by transforming XML to XAML using XSLT? Any other suggestion?

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  • Is there a way that I can force mod_perl to re-use buffer memory?

    - by Pavel Georgiev
    Hi, I have a Perl script running in mod_perl that needs to write a large amount of data to the client, possibly over a long period. The behavior that I observe is that once I print and flush something, the buffer memory is not reclaimed even though I rflush (I know this can't be reclaimed back by the OS). Is that how mod_perl operates and is there a way that I can force it to periodically free the buffer memory, so that I can use that for new buffers instead of taking more from the OS?

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