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  • WPF and LINQ/SQL - how and where to keep track of changes?

    - by Groky
    I have a WPF application built using the MVVM pattern: My Models come from LINQ to SQL. I use the Repository Pattern to abstract away the DataContext. My ViewModels have a reference to a Model. Setting a property on the ViewModel causes that value to be written through to the Model. As you can see, my data is stored in my Model, and changes are therefore tracked by my DataContext. However, in this question I read: The guidelines from the MSDN documentation on the DataContext class are what I would recommend following: In general, a DataContext instance is designed to last for one "unit of work" however your application defines that term. A DataContext is lightweight and is not expensive to create. A typical LINQ to SQL application creates DataContext instances at method scope or as a member of short-lived classes that represent a logical set of related database operations. How do you track your changes? In your DataContext? In your ViewModel? Elsewhere?

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  • Thread-safety of read-only memory access

    - by Edmund
    I've implemented the Barnes-Hut gravity algorithm in C as follows: Build a tree of clustered stars. For each star, traverse the tree and apply the gravitational forces from each applicable node. Update the star velocities and positions. Stage 2 is the most expensive stage, and so is implemented in parallel by dividing the set of stars. E.g. with 1000 stars and 2 threads, I have one thread processing the first 500 stars and the second thread processing the second 500. In practice this works: it speeds the computation by about 30% with two threads on a two-core machine, compared to the non-threaded version. Additionally, it yields the same numerical results as the original non-threaded version. My concern is that the two threads are accessing the same resource (namely, the tree) simultaneously. I have not added any synchronisation to the thread workers, so it's likely they will attempt to read from the same location at some point. Although access to the tree is strictly read-only I am not 100% sure it's safe. It has worked when I've tested it but I know this is no guarantee of correctness! Questions Do I need to make a private copy of the tree for each thread? Even if it is safe, are there performance problems of accessing the same memory from multiple threads?

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  • How can I accelerate the generation of the an MD5 Checksum within vb.net?

    - by Richard
    I'm working with some very large files residing on P2 (Panasonic) cards. Part of the process we employ is to first generate a checksum of the file we are going to copy, then copy the file, then run a checksum on the file to confirm that it copied OK. The problem is, is that files are large (70 GB+) and take a long time to complete. It's an issue since we will eventually be dealing with thousands of these files. I would like to find a faster way to generate the checksum other than using the System.Security.Cryptography.MD5CryptoServiceProvider I don't care if this means using a specialized hardware card, provided it works and is not to ungodly expensive. I would prefer to have a method of encoding that provided some feedback as to how far the process has gone along so I can display it like I do now. The application is written in vb.net. I would prefer to be able to use it as component, library, reference within my application, but I'm willing to call an outside application if there is enough improvement in the speed of generating the checksum. Needless to say, the checksum must be consistent and correct. :-) Thank you in advance for your time and efforts, Richard

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  • Conditional insert as a single database transaction in HSQLDB 1.8?

    - by Kevin Pauli
    I'm using a particular database table like a "Set" data structure, i.e., you can attempt to insert the same row several times, but it will only contain one instance. The primary key is a natural key. For example, I want the following series of operations to work fine, and result in only one row for Oklahoma: insert into states_visited (state_name) values ('Oklahoma'); insert into states_visited (state_name) values ('Texas'); insert into states_visited (state_name) values ('Oklahoma'); I am of course getting an error due to the duplicate primary key on subsequent inserts of the same value. Is there a way to make the insert conditional, so that these errors are not thrown? I.e. only do the the insert if the natural key does not already exist? I know I could do a where clause and a subquery to test for the row's existence first, but it seems that would be expensive. That's 2 physical operations for one logical "conditional insert" operation. Anything like this in SQL? FYI I am using HSQLDB 1.8

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  • Fast, Unicode-capable, cross-platform programmer's text editor that shows invisibles like ZWSP?

    - by Roger_S
    Our publishing workflow includes Windows and Linux machines (there are some Macs too, but not in the critical-path workflow). Many texts include both English and Khmer and are marked-up in XML. XML Copy Editor is the best cross-platform open-source XML editor I've discovered. It utilizes the Scintilla editing component, which is generally good with Unicode but which does not enable non-printing or invisible characters like U+200B (zero-width space) and U+200C (zero-width non-joiner) to be displayed. Khmer does not separate words with a space character as Western languages do, so ZWSP is used in electronic texts to enable applications to break lines easily. Ideally I'd edit the markup and the content in a single editor, but XML awareness is less important at times than being able to display invisibles. (OpenOffice.org Writer and Microsoft Word are the only two apps I know that will display ZWSP. They are not suitable for the markup and text manipulations that need to be done to prepare manuscripts for publication, unfortunately, although I guess they're fine for authoring.) I tried out a promising editor last week, but a search-and-replace regex operation that took under a second in TextPad 4.7.3 lasted over twenty seconds. So I want to mention that speed and the ability to handle large (up to 150mb) files is also a concern. Is there a good, fast, free or not too expensive text editor, with versions on Windows and Linux and maybe mac too, Unicode-aware and capable of displaying invisibles like ZWSP? That has syntax highlighting, can handle large files and is customizable enough that I won't tear my hair out in frustration? Thanks, Roger_S

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  • JAVA MySql multiple word search

    - by user1703849
    i have a database in MySql that has a name column in it which contains several words(description). I am connected to database with java through eclipse. I have a search, that returns results if only name field contains one word. id: name: info: type: 1 balloon big red balloon big 2 house expensive beautiful luxury 3 chicken wings deep fried wings tasty these are just random words but as an example my search can only see ex. balloon and then show info, but if i type chicken wings, it does nothing. so it possible somehow to search from columns with multiple words? this is my search code below import java.io.*; import java.sql.*; import java.util.*; class Search { public static void main(String[] args) { Scanner inp``ut = new Scanner(System.in); try { Connection con = DriverManager.getConnection( "jdbc:mysql://example/mydb", "user", "password"); Statement stmt = (Statement) con.createStatement(); System.out.print("enter search: "); String name = input.next(); String SQL = "SELECT * FROM menu where name LIKE '" + name + "'"; ResultSet rs = stmt.executeQuery(SQL); while (rs.next()) { System.out.println("Name: " +rs.getString("name")); System.out.println("Description: " + rs.getString("info") ); System.out.println("Price: " + rs.getString("Price")); } } catch (Exception e) { System.out.println("ERROR: " + e.getMessage()); } } }

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  • regressions with many nested categorical covariates

    - by eric
    I have a few hundred thousand measurements where the dependent variable is a probability, and would like to use logistic regression. However, the covariates I have are all categorical, and worse, are all nested. By this I mean that if a certain measurement has "city - Phoenix" then obviously it is certain to have "state - Arizona" and "country - U.S." I have four such factors - the most granular has some 20k levels, but if need be I could do without that one, I think. I also have a few non-nested categorical covariates (only four or so, with maybe three different levels each). What I am most interested in is prediction - given a new observation in some city, I would like to know the relevant probability/dependent variable. I am not interested as much in the related inferential machinery - standard deviations, etc - at least as of now. I am hoping I can afford to be sloppy. However, I would love to have that information unless it requires methods that are more computationally expensive. Does anyone have any advice on how to attack this? I have looked into mixed effects, but am not sure it is what I am looking for.

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  • How hide some nodes in Richfaces Tree (do not render nodes by condition)?

    - by VestniK
    I have a tree of categories and courses in my SEAM application. Courses may be active and inactive. I want to be able to show only active or all courses in my tree. I've decided to always build complete tree in my PAGE scope component since building this tree is quite expensive operation. I have boolean flag courseActive in the data wrapped by TreeNode<T>. Now I can't find the way to show courses node only if this flag is true. The best result I've achieved with the following code: <h:outputLabel for="showInactiveCheckbox" value="show all courses: "/> <h:selectBooleanCheckbox id="showInactiveCheckbox" value="#{categoryTreeEditorModel.showAllCoursesInTree}"> <a4j:support event="onchange" reRender="categoryTree"/> </h:selectBooleanCheckbox> <rich:tree id="categoryTree" value="#{categoryTree}" var="item" switchType="ajax" ajaxSubmitSelection="true" reRender="categoryTree,controls" adviseNodeOpened="#{categoryTreeActions.adviseRootOpened}" nodeSelectListener="#{categoryTreeActions.processSelection}" nodeFace="#{item.typeName}"> <rich:treeNode type="Category" icon="..." iconLeaf="..."> <h:outputText value="#{item.title}"/> </rich:treeNode> <rich:treeNode type="Course" icon="..." iconLeaf="..." rendered="#{item.courseActive or categoryTreeEditorModel.showAllCoursesInTree}"> <h:outputText rendered="#{item.courseActive}" value="#{item.title}"/> <h:outputText rendered="#{not item.courseActive}" value="#{item.title}" style="color:#{a4jSkin.inactiveTextColor}"/> </rich:treeNode> </rich:tree> the only problem is if some node is not listed in any rich:treeNode it just still shown with title obtained by Object.toString() method insted of being hidden. Does anybody know how to not show some nodes in the Richfases tree according to some condition?

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  • Avoid slowdowns while using off-site database

    - by Anders Holmström
    The basic layout of my problem is this: Website (ASP.NET/C#) hosted at a dedicated hosting company (location 1) Company database (SQL Server) with records of relevant data (location 2). Location 1 & 2 connected through VPN. Customer visiting the website and wanting to pull data from the company database. No possibility of changing the server locations or layout (i.e. moving the website to an in-office server isn't possible). What I want to do is figure out the best way to handle the data acces in this case, minimizing the need for time-expensive database calls over the VPN. The first idea I'm getting is this: When a user enters the section of the website needing the DB data, you pull all the needed tables from the database into a in-memory dataset. All subsequent views/updates to the data is done on this dataset. When the user leaves (logout, session timeout, browser closed etc) the dataset gets sent to the SQL server. I'm not sure if this is a realistic solution, and it obviously has some problems. If two web visitors are performing updates on the same data, the one finishing up last will have their changes overwriting the first ones. There's also no way of knowing you have the latest data (i.e. if a customer pulls som info on their projects and we update this info while they are viewing them, they won't see these changes PLUS the above overwriting issue will arise). The other solution would be to somehow aggregate database calls and make sure they only happen when you need them, e.g. during data updates but not during data views. But then again the longer a pause between these refreshing DB calls, the bigger a chance that the data view is out of date as per the problem described above. Any input on the above or some fresh ideas would be most welcome.

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  • Ways to implement tags - pros and cons of each

    - by bobobobo
    Related Using SO as an example, what is the most sensible way to manage tags if you anticipate they will change often? Way 1: Seriously denormalized (comma delimited) table posts +--------+-----------------+ | postId | tags | +--------+-----------------+ | 1 | c++,search,code | Here tags are comma delimited. Pros: Tags are retrieved at once with a single select query. Updating tags is simple. Easy and cheap to update. Cons: Extra parsing on tag retrieval, difficult to count how many posts use which tags. (alternatively, if limited to something like 5 tags) table posts +--------+-------+-------+-------+-------+-------+ | postId | tag_1 | tag_2 | tag_3 | tag_4 | tag_5 | +--------+-------+-------+-------+-------+-------+ | 1 | c++ |search | code | | | Way 2: "Slightly normalized" (separate table, no intersection) table posts +--------+-------------------+ | postId | title | +--------+-------------------+ | 1 | How do u tag? | table taggings +--------+---------+ | postId | tagName | +--------+---------+ | 1 | C++ | | 1 | search | Pros: Easy to see tag counts (count(*) from taggings where tagName='C++'). Cons: tagName will likely be repeated many, many times. Way 3: The cool kid's (normalized with intersection table) table posts +--------+---------------------------------------+ | postId | title | +--------+---------------------------------------+ | 1 | Why is a raven like a writing desk? | table tags +--------+---------+ | tagId | tagName | +--------+---------+ | 1 | C++ | | 2 | search | | 3 | foofle | table taggings +--------+---------+ | postId | tagId | +--------+---------+ | 1 | 1 | | 1 | 2 | | 1 | 3 | Pros: No repeating tag names. More girls will like you. Cons: More expensive to change tags than way #1.

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  • How can you change the font color of a theme-enabled control?

    - by Edouard Westphal
    Yes, this is again this question: How can I change the font color of a TCheckBox (or any handled control) with Delphi7-Delphi2007 on a themes enabled application? After reading a lot on the internet and on this site, I found 4 kinds of answer: and Most populare (even from QC): You can't, it's designed like that by Microsoft. Create a component that let you draw it like you want. Buy expensive component set that draws like you want. Do not use themes. OK, but I am still unhappy with that. Giving a user colored feedback for the status of a property/data he has on a form, seems legitimate to me. Then I just installed the MSVC# 2008 Express edition, and what a surprise, they can change the color of the font (property ForeColor of the check box) Then what? It does not seem to be a "it's designed like that, by Microsoft." then now the question again: How can I change the font color of a TCheckBox (or any handled control) with Delphi 7 through Delphi 2007 on a theme-enabled application?

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  • How long is the time frame between context switches on Windows?

    - by mattcodes
    Reading CLR via C# 2.0 (I dont have 3.0 with me at the moment) Is this still the case: If there is only one CPU in a computer, only one thread can run at any one time. Windows has to keep track of the thread objects, and every so often, Windows has to decide which thread to schedule next to go to the CPU. This is additional code that has to execute once every 20 milliseconds or so. When Windows makes a CPU stop executing one thread's code and start executing another thread's code, we call this a context switch. A context switch is fairly expensive because the operating system has to: So circa CLR via C# 2.0 lets say we are on Pentium 4 2.4ghz 1 core non-HT, XP. Every 20 milliseconds? Where a CLR thread or Java thread is mapped to an OS thread only a maximum of 50 threads per second may get a chance to to run? I've read that context switching is very fast in mircoseconds here on SO, but how often roughly (magnitude style guesses) will say a modest 5 year old server Windows 2003 Pentium Xeon single core give the OS the opportunity to context switch? 20ms in the right area? I dont need exact figures I just want to be sure that's in the right area, seems rather long to me.

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  • When to use @Singleton in a Jersey resource

    - by dexter
    I have a Jersey resource that access the database. Basically it opens a database connection in the initialization of the resource. Performs queries on the resource's methods. I have observed that when I do not use @Singleton, the database is being open at each request. And we know opening a connection is really expensive right? So my question is, should I specify that the resource be singleton or is it really better to keep it at per request especially when the resource is connecting to the database? My resource code looks like this: //Use @Singleton here or not? @Path(/myservice/) public class MyResource { private ResponseGenerator responser; private Log logger = LogFactory.getLog(MyResource.class); public MyResource() { responser = new ResponseGenerator(); } @GET @Path("/clients") public String getClients() { logger.info("GETTING LIST OF CLIENTS"); return responser.returnClients(); } ... // some more methods ... } And I connect to the database using a code similar to this: public class ResponseGenerator { private Connection conn; private PreparedStatement prepStmt; private ResultSet rs; public ResponseGenerator(){ Class.forName("org.h2.Driver"); conn = DriverManager.getConnection("jdbc:h2:testdb"); } public String returnClients(){ String result; try{ prepStmt = conn.prepareStatement("SELECT * FROM hosts"); rs = prepStmt.executeQuery(); ... //do some processing here ... } catch (SQLException se){ logger.warn("Some message"); } finally { rs.close(); prepStmt.close(); // should I also close the connection here (in every method) if I stick to per request // and add getting of connection at the start of every method // conn.close(); } return result } ... // some more methods ... } Some comments on best practices for the code will also be helpful.

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  • What are the general strategies for the server of an FPS multiplayer game to update its clients?

    - by Hooray Im Helping
    A friend and I were having a discussion about how a FPS server updates the clients connected to it. We watched a video of a guy cheating in Battlefield: Bad Company 2 and saw how it highlighted the position of enemies on the screen and it got us thinking. His contention was that the server only updates the client with information that is immediately relevant to the client. I.e. the server won't send information about enemy players if they are too far away from the client or out of the client's line of sight for reasons of efficiency. He was unsure though - he brought up the example of someone hiding behind a rock, not able to see anyone. If the player were suddenly to pop up where he had three players in his line of sight, there would be a 50ms delay before they were rendered on his screen while the server transmitted the necessary information. My contention was the opposite: that the server sends the client all the information about every player and lets the client sort out what is allowed and what isn't. I figured it would actually be less expensive computationally for the server to just send everything to the client and let the client do the heavy lifting, so to speak. I also figured this is how cheat programs work - they intercept the server packets, get the location of enemies, then show them on the client's view. So the question: What are some general policies or strategies a modern first person shooter server employs to keep its clients updated?

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  • What's the best way to get a bunch of rows from MySQL if you have an array of integer primary keys?

    - by Evan P.
    I have a MySQL table with an auto-incremented integer primary key. I want to get a bunch of rows from the table based on an array of integers I have in memory in my program. The array ranges from a handful to about 1000 items. What's the most efficient query syntax to get the rows? I can think of a few: "SELECT * FROM thetable WHERE id IN (1, 2, 3, 4, 5)" (this is what I do now) "SELECT * FROM thetable where id = 1 OR id = 2 OR id = 3" Multiple queries of the form "SELECT * FROM thetable WHERE id = 1". Probably the most friendly to the query cache, but expensive due to having lots of query parsing. A union, like "SELECT * FROM thetable WHERE id = 1 UNION SELECT * FROM thetable WHERE id = 2 ..." I'm not sure if MySQL caches the results of each query; it's also the most verbose format. I think using the NoSQL interface in MySQL 5.6+ would be the most efficient way to do this, but I'm not yet up to MySQL 5.6.

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  • What's the best approach for getting into VS2010, C# 4, and WPF if my background is in C++/MFC

    - by Canacourse
    All my past programming experience has been in C++ on VS2003/8, Mostly service based and completely self taught. 2 Years ago I had to create my first real GUI app and (Foolishly) choose MFC. I got the app working but it took a long time & was a bit of a nightmare to learn MCF (and its many shortcomings) but I ended up with a reliable workable app which was difficult to change or extend. Again I have to create another GUI app more complex than the first and again this will be created from scratch and will only ever be used on windows. I had put off learning C# for a long time but not wishing to re-visit MFC have decided that the new application with be birthed in VS2010 and WPF 4 will be the midwife. Trying to avoid the several expensive (Time wise) mistakes I made previously. Im looking for for good books/tutorials on the current versions of C# 4 & WPF 4 and also general advice on the best approach. The application will do several things one of them would persisting info in a SQL DB. So Im thinking LINQ for that? Please chip in...

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  • How to optimize paging for large in memory database

    - by snakefoot
    I have an application where the entire database is implemented in memory using a stl-map for each table in the database. Each item in the stl-map is a complex object with references to other items in the other stl-maps. The application works with a large amount of data, so it uses more than 500 MByte RAM. Clients are able to contact the application and get a filtered version of the entire database. This is done by running through the entire database, and finding items relevant for the client. When the application have been running for an hour or so, then Windows 2003 SP2 starts to page out parts of the RAM for the application (Eventhough there is 16 GByte RAM on the machine). After the application have been partly paged out then a client logon takes a long time (10 mins) because it now generates a page fault for each pointer lookup in the stl-map. I can see it is possible to tell Windows to lock memory in RAM, but this is generally only recommended for device drivers, and only for "small" amounts of memory. I guess a poor mans solution could be to loop through the entire memory database, and thus tell Windows we are still interested in keeping the datamodel in RAM. I guess another poor mans solution could be to disable the pagefile completely on Windows. I guess the expensive solution would be a SQL database, and then rewrite the entire application to use a database layer. Then hopefully the database system will have implemented means to for fast access. Are there other more elegant solutions ?

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  • What would be a better implementation of shared variable among subclass

    - by Churk
    So currently I have a spring unit testing application. And it requires me to get a session cookie from a foreign authentication source. Problem what that is, this authentication process is fairly expensive and time consuming, and I am trying to create a structure where I am authenticate once, by any subclass, and any subsequent subclass is created, it will reuse this session cookie without hitting the authentication process again. My problem right now is, the static cookie is null each time another subclass is created. And I been reading that using static as a global variable is a bad idea, but I couldn't think of another way to do this because of Spring framework setting things during run time and how I would set the cookie so that all other classes can use it. Another piece of information. The variable is being use, but is change able during run time. It is not a single user being signed in and used across the board. But more like a Sub1 would call login, and we have a cookie. Then multiple test will be using that login until SubX will come in and say, I am using different credential, so I need to login as something else. And repeats. Here is a outline of my code: public class Parent implements InitializingBean { protected static String BASE_URL; public static Cookie cookie; ... All default InitializingBean methods ... afterPropertiesSet() { cookie = // login process returns a cookie } } public class Sub1 extends Parent { @resource public String baseURL; @PostConstruct public void init() { // set parents with my baseURL; BASE_URL = baseURL; } public void doSomething() { // Do something with cookie, because it should have been set by parent class } } public class Sub2 extends Parent { @resource public String baseURL; @PostConstruct public void init() { // set parents with my baseURL; BASE_URL = baseURL; } public void doSomethingElse() { // Do something with cookie, because it should have been set by parent class } }

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  • First Time Architecturing?

    - by cam
    I was recently given the task of rebuilding an existing RIA. The new RIA that I've designed is based on Silverlight, with a WCF service to connect to MS SQL Server. This is my first time doing something like this, so I'm not sure how to design the entire thing. Basically, the client can look through graphs of "stocks" (allowing the client to choose different time periods, settings, etc). I've written the whole application essentially, but I'm not sure how to put it together. The graphs are supposed to be directly based on the database, and to create the datapoints on the graph, some calculations need to be done (not very expensive ones). The problem I'm having is to decide where to put the calculations (client or serverside? Or half and half?) What factors should I look for to help me decide where the calculations should be done? And how can I go about optimizing this (caching, etc)? Obviously this is a very broad subject, so I'm not expecting an immediate answer, but any help/pointing in the right direction/resources would be appreciated.

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  • nhibernate sessionfactory instance more than once on web service

    - by Manuel
    Hello, i have a web service that use nhibernate. I have a singleton pattern on the repositorry library but on each call the service, it creates a new instance of the session factory wich is very expensive. What can i do? region Atributos /// <summary> /// Session /// </summary> private ISession miSession; /// <summary> /// Session Factory /// </summary> private ISessionFactory miSessionFactory; private Configuration miConfiguration = new Configuration(); private static readonly ILog log = LogManager.GetLogger(typeof(NHibernatePersistencia).Name); private static IRepositorio Repositorio; #endregion #region Constructor private NHibernatePersistencia() { //miConfiguration.Configure("hibernate.cfg.xml"); try { miConfiguration.Configure(); this.miSessionFactory = miConfiguration.BuildSessionFactory(); this.miSession = this.SessionFactory.OpenSession(); log.Debug("Se carga NHibernate"); } catch (Exception ex) { log.Error("No se pudo cargar Nhibernate " + ex.Message); throw ex; } } public static IRepositorio Instancia { get { if (Repositorio == null) { Repositorio = new NHibernatePersistencia(); } return Repositorio; } } #endregion #region Propiedades /// <summary> /// Sesion de NHibernate /// </summary> public ISession Session { get { return miSession.SessionFactory.GetCurrentSession(); } } /// <summary> /// Sesion de NHibernate /// </summary> public ISessionFactory SessionFactory { get { return this.miSessionFactory; } } #endregion In wich way can i create a single instance for all services?

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  • Performance issue finding weekdays over a given period

    - by Oysio
    I have some methods that return the number of weekdays between two given dates. Since calling these methods become very expensive to call when the two dates lie years apart, I'm wondering how these methods could be refactored in a more efficient way. The returned result is correct but I feel that the iphone processor is struggling to keep up and consequently freezes up the application when I would call these methods over a period of say 10years. Any suggestions ? //daysList contains all weekdays that need to be found between the two dates -(NSInteger) numberOfWeekdaysFromDaysList:(NSMutableArray*) daysList startingFromDate:(NSDate*)startDate toDate:(NSDate*)endDate { NSInteger retNumdays = 0; for (Day *dayObject in [daysList objectEnumerator]) { if ([dayObject isChecked]) { retNumdays += [self numberOfWeekday:[dayObject weekdayNr] startingFromDate:startDate toDate:endDate]; } } return retNumdays; } -(NSInteger) numberOfWeekday:(NSInteger)day startingFromDate:(NSDate*)startDate toDate:(NSDate*)endDate { NSInteger numWeekdays = 0; NSDate *nextDate = startDate; NSComparisonResult result = [endDate compare:nextDate]; //Do while nextDate is in the past while (result == NSOrderedDescending || result == NSOrderedSame) { if ([NSDate weekdayFromDate:nextDate] == day) { numWeekdays++; } nextDate = [nextDate dateByAddingDays:1]; result = [endDate compare:nextDate]; } return numWeekdays; }

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  • Programatically adding,changing and removing controls bound to model objects (MVVM)

    - by Ittai
    I have the following scenario and I'm trying to decide how it can and should be implemented in silverlight and c# via MVVM. Scenario: I have the following objects in my scenario: MyModel, MyModelControl, MyView and MyViewModel. MyModelcontrol is a custom UserControl of mine and the rest I think are pretty much self explanatory. MyViewModel is a Subscriber of a message which hands it a Collection<MyModel> newCol and let's mark curCol as the current Collection<MyModel> that MyViewModel holds. I then want to programatically add MyModelControl controls for each MyModel instance which belongs to newCol and not to curCol. I also want to bind the MyModelControl instance to the corresponding MyModel instance. In a similar manner I want to remove the controls which don't belong now to the collection and I want to update a property for those which belong to both. I do not want to remove all controls which belong to curCol and then add all controls for newCol as the creation of MyModelControl is "expensive". I'd appreciate help with how this should be implemented in SL as I'm new to it and to the MVVM pattern. Comments regarding the design would also be welcomed. B.T.W This will run on Windows Phone 7 so I think there are some limitations on versions, if this is an issue please comment and I'll verify which versions exactly I can use on the phone.

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  • Is the Subversion 'stack' a realistic alternative to Team Foundation Server?

    - by Robert S.
    I'm evaluating Microsoft Team Foundation Server for my customer, who currently uses Visual SourceSafe and nothing else. They have explicitly expressed a desire to implement a more rigid and process-driven environment as their application is in production and they have future releases to consider. The particular areas I'm trying to cover are: Configuration management (e.g., source control) Change management (workflow and doco for change requests, tasks) Release management (builds and deployments) Incident and problem management (issues and bugs) Document management (similar to source control, but available via web) Code analysis constraints on check-ins A testing framework Reporting Visual Studio 2008 integration TFS does all of these things quite well, but it's expensive and complex to maintain, and the inexpensive Workgroup edition doesn't scale. We don't get TFS as part of our MSDN subscription. Those problems can be overcome, but before I tell my customer to go the TFS route, which in itself isn't a terrible thing, I wanted to evaluate the alternatives. I know Subversion is often suggested for its configuration management/source control, but what about the other areas? Would a combination of Subversion/NUnit/Wiki/CruiseControl/NAnt/something else satisfy all of these requirements? What tools do I need to include in my evaluation? Or should I just bite the bullet and go with TFS since we're already invested in the Microsoft stack?

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  • Having to insert a record, then update the same record warrants 1:1 relationship design?

    - by dianovich
    Let's say an Order has many Line items and we're storing the total cost of an order (based on the sum of prices on order lines) in the orders table. -------------- orders -------------- id ref total_cost -------------- -------------- lines -------------- id order_id price -------------- In a simple application, the order and line are created during the same step of the checkout process. So this means INSERT INTO orders .... -- Get ID of inserted order record INSERT into lines VALUES(null, order_id, ...), ... where we get the order ID after creating the order record. The problem I'm having is trying to figure out the best way to store the total cost of an order. I don't want to have to create an order create lines on an order calculate cost on order based on lines then update record created in 1. in orders table This would mean a nullable total_cost field on orders for starters... My solution thus far is to have an order_totals table with a 1:1 relationship to the orders table. But I think it's redundant. Ideally, since everything required to calculate total costs (lines on an order) is in the database, I would work out the value every time I need it, but this is very expensive. What are your thoughts?

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  • Client Server communication in Java - which approach to use?

    - by markovuksanovic
    I have a typical client server communication - Client sends data to the server, server processes that, and returns data to the client. The problem is that the process operation can take quite some time - order of magnitude - minutes. There are a few approaches that could be used to solve this. Establish a connection, and keep it alive, until the operation is finished and the client receives the response. Establish connection, send data, close the connection. Now the processing takes place and once it is finished the server could establish a connection to the client to send the data. Establish a connection, send data, close the connection. Processing takes place. client asks server, every n minutes/seconds if the operation is finished. If the processing is finished the client fetches the data. I was wondering which approach would be the best way to use. Is there maybe some "de facto" standard for solving this problem? How "expensive" is opening a socket in Java? Solution 1. seems pretty nasty to me, but 2. and 3. could do. The problem with solution 2. is that the server needs to know on which port the client is listening, while solution 3. adds some network overhead.

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