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  • Why isn't it possible to update an ObservableCollection from a different thread?

    - by MainMa
    In a multi-threaded WPF application, it is not possible to update an ObservableCollection from a thread other than WPF window thread. I know there are workarounds, so my question is not how to avoid the "This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread" exception. My question is, why there is such an exception? Why wasn't it possible to allow collection updates from any thread? Personally, I don't see any reason to block UI update when ObservableCollection is changed from other threads. If two threads (including parallel ones) are accessing the same object, one listening for changes of object properties through events, the other one doing changes, it will always work, at least if locks are used properly. So, what are the reasons?

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  • MySQL - accessing a table sum and compare to another table?

    - by assignment_operator
    This is for a homework assignment. I just plain don't understand how to do it. The instructions for this particular question is: List the branch name for all branches that have at least one book that has at least 4 copies on hand. Where the tables in question are: Branch: BranchName | BranchId Henry Downtown | 1 16 Riverview | 2 Henry On The Hill | 3 Inventory: BookId | BranchId | OnHand 1 | 1 | 2 2 | 3 | 4 3 | 1 | 8 4 | 3 | 1 5 | 1 | 2 6 | 2 | 3 From what I understand, I can get the number of OnHand per branch name with: SELECT BranchName, SUM(OnHand) FROM Branch B, Inventory I WHERE B.BranchId = I.BranchId GROUP BY BranchName; but I don't get how I'd do the comparison between the sum of OnHand per branch and 4. Any help would be appreciated, guys!

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  • Which one is better to have auto-implemented property with private setter or private field and property just getter?

    - by PLB
    My question may be a part of an old topic - "properties vs fields". I have situation where variable is read-only for outside class but needs to modified inside a class. I can approach it in 2 ways: First: private Type m_Field; public Type MyProperty { get { return m_Field; } } Second: public Type MyProperty { get; private set; } After reading several articles (that mostly covered benefits of using public properties instead of public fields) I did not get idea if the second method has some advantage over the first one but writing less code. I am interested which one will be better practice to use in projects (and why) or it's just a personal choice. Maybe this question does not belong to SO so I apologize in advance.

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  • Google Play: how dev can give (already purchased) app to customer as a gift?

    - by Tertium
    Yes, SO, I know, it's not a "programmer's" question:) But customers sometimes help us (devs) with our code, so we (devs) shold be grateful. I think answer to my question will be useful for all fellow android devs. User has purchased my app. Refund period (15min) is over of course. Now I'd like to return money to him as a gift, because he helped me in testing a little. If I refund the entire order in Checkout-Orders will user keep my app 'purchased'? I mean will he be able to uninstall and install it again from GooglePlay-MyApps and will app be marked "purchased"? Will Google LVL accept him to run the app? I've done such refunds before, but then they called it "Android Market", and refund was 12h, and there were no LVL. Maybe somebody know another way to make a small gift using Google Play?

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  • How do I run an array through an IF statement in rails?

    - by codyvbrown
    I am creating an application that highlights user messages from a stream based on whether or not the user has been 'vouched'. It works fine if it's setup for a single author. For example controller: @vouch = Vouch.last.vouched_user_nickname view: <% Twitter::Search.new(params[:id]).each do |tweet| %> <li> <%= image_tag tweet.profile_image_url %> <% if @vouch.include? tweet.from_user %> <div class="flit_message_containerh"> <u> <a href="http://twitter.com/<%= tweet.from_user %>"> <%= tweet.from_user %></a></u> <%= linkup_mentions(auto_link(h tweet.text)) %> <div class="time_ago"> <%= link_to distance_of_time_in_words_to_now(tweet.created_at) , tweet %> <% else %> <div class="flit_message_container"> <u> <a href="http://twitter.com/<%= tweet.from_user %>"> <%= tweet.from_user %></a></u> <%= linkup_mentions(auto_link(h tweet.text)) %> <div class="time_ago"> <%= link_to distance_of_time_in_words_to_now(tweet.created_at) , tweet %> <% end %> But I'm having trouble doing it for multiple user nicknames. @vouch = Vouch.find(:all, :select => "vouched_user_nickname", :group => 'vouched_user_nickname' ) Any ideas would be greatly appreciated. I'm a rails noob.

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  • Java constructor using generic types

    - by user37903
    I'm having a hard time wrapping my head around Java generic types. Here's a simple piece of code that in my mind should work, but I'm obviously doing something wrong. Eclipse reports this error in BreweryList.java: The method initBreweryFromObject() is undefined for the type <T> The idea is to fill a Vector with instances of objects that are a subclass of the Brewery class, so the invocation would be something like: BreweryList breweryList = new BreweryList(BrewerySubClass.class, list); BreweryList.java package com.beerme.test; import java.util.Vector; public class BreweryList<T extends Brewery> extends Vector<T> { public BreweryList(Class<T> c, Object[] j) { super(); for (int i = 0; i < j.length; i++) { T item = c.newInstance(); // initBreweryFromObject() is an instance method // of Brewery, of which <T> is a subclass (right?) c.initBreweryFromObject(); // "The method initBreweryFromObject() is undefined // for the type <T>" } } } Brewery.java package com.beerme.test; public class Brewery { public Brewery() { super(); } protected void breweryMethod() { } } BrewerySubClass.java package com.beerme.test; public class BrewerySubClass extends Brewery { public BrewerySubClass() { super(); } public void androidMethod() { } } I'm sure this is a complete-generics-noob question, but I'm stuck. Thanks for any tips!

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  • Refactor C++ code to use a scripting language?

    - by Justin Ardini
    Background: I have been working on a platformer game written in C++ for a few months. The game is currently written entirely in C++, though I am intrigued by the possibility of using Lua for enemy AI and possibly some other logic. However, the project was designed without Lua in mind, and I have already written working C++ code for much of the AI. I am hoping Lua can improve the extensibility of the game, but don't know if it would make sense to convert existing C++ code into Lua. The question: When, if ever, is it appropriate to take fully functional C++ code and refactor it into a scripting language like Lua? The question is intentionally a bit vague, so feel free give answers that are not relevant to the given background.

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  • Record Name field in DNS responce

    - by Lescott
    I just read about DNS protocol, and found, that the name field can be writen in two ways: lenght of the next label the label lenght of the next label the label ... zero-byte pointer to the previous name field Next is the original article fragment: The Resource Record Name field is encoded in the same way as the Question Name field unless the name is already present elsewhere in the DNS message, in which case a 2-byte field is used in place of a length-value encoded name and acts as a pointer to the name that is already present. So, my question is, how can I determine the first or the second way is using in a package?

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  • Position DIV relative to containing DIV Without Moving Other Stuff

    - by yar
    [I'm not sure if this question has been asked, though I've looked around a bit.] I have a DIV inside a DIV. I would like the inner DIV to have a certain position inside the outer div. I'm having some success with this position: absolute; top: 0px;right:0px; but all other divs are getting moved around. I just want it to float on top of the other stuff (float didn't work, of course). Thanks! Edit: The outer div is relative, and I'd like the inner to move with it when the browser is resized. Edit: Sorry, I've figured out the question (but not the answer): if I use right:0px, the inner div stops moving relative to the outer div and starts moving relative to the browser window. Why would that be?

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  • jquery - how is multiple selection working in this example?

    - by hatorade
    The relevant snippet of HTML: <span class="a"> <div class="fieldname">Question 1</div> <input type="text" value="" name="q1" /> </span> The relevant jQuery: $.each($('.a'), function(){ $thisField = $('.fieldname', $(this)); }); What exactly is being set to $thisField? If my understanding of multiple selectors in jQuery is correct, it should be grabbing the outer <span> element AND the inner <div> element. But for some reason, if I use $thisField.prepend("hi"); it ends up putting hi right before the text Question 1, but not before <div>. I thought multiple selectors would grab both elements, and that prepend() adds hi to the beginning of BOTH elements, not just the <div>

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  • Tutorial needed to learn Microsoft BI

    - by Zerotoinfinite
    I am a .NET developer and have a little experience in Sql Server. As we all know that .NET developer mostly deals with stored procedures in Sql Server. I am willing to learn BI (SSIS,SSRS,SSAS) from home. I have seen some article but I don't think that's going to work for me. I am seeking some Free video tutorials I can get to learn BI. Imp: I am asking this question here because I believe that many of you are genius BI and .NET developers so you guys can help me figure out which tutorial will take benift from my .net skills. Apologize : I used free in my question. I am guilt to say that I am one of the guy who is not willing to invest but the reason is this that currently I am Jobless. :-(

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  • Hard drive randomly sppeeding up

    - by Glenn Taylor
    Having a weird issue with my hard drive. Running Windows 7 with an I5 processor. At random times the hard drive will start running at top speed and gradually return to normal over the next two minutes or so. Going to Resource Monitor it shows a variety of things with high read or write numbers. Log files NTFS volume log, Windows prefetch, System/user/appdata, and Program data Norton are the usual top ones listed. This just started about three months ago although the computer is about 3 years old. Have run in safe mode with internet over the weekend going to all of my usual sites with no such speed up. Question 1 - what can be causing this? Question 2 - how can I find out where data is being sent(especially if over the net)? Thank you.

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  • Why don't hardware failures show up at the programming language level?

    - by Julian Cienfuegos
    I am wondering if anyone can give my a good answer, or at least point me in the direction of a good reference to the following question: How come I have never heard of a computer breaking in a very fundamental way? How come when I declare x to be a double it stays as a double? How come there is never a short circuit that robs it of some bytes and makes it an integer? Why do we have faith that when we initialize x to 10, there will never be a power surge that will cause it to become 11, or something similar? I think I need a better understanding of memory. Thanks, and please don't bash me over the head for such a simple/abstract question.

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  • ideas for simple objects for day to day web-dev use?

    - by Joel
    Dang-I know this is a subjective question so will probably get booted off/locked, but I'll try anyway, because I don't know where else to ask (feel free to point me to a better place to ask this!) I'm just wrapping my head around oop with PHP, but I'm still not using frameworks or anything. I'd like to create several small simple objects that I could use in my own websites to better get a feel for them. Can anyone recommend a list or a resource that could point me to say 10 day-to-day objects that people would use in basic websites? The reason I'm asking is because I'm confusing myself a bit. For example, I was thinking of a "database connection" object, but then I'm just thinking that is just a function, and not really an "object"?? So the question is: What are some examples of objects used in basic PHP websites (not including "shopping cart" type websites) Thanks!

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  • iPhone Notifications is possible to...

    - by user331769
    Hi to all, I read more post regarding iPhone notification, and I have a simple question.... Where a device receive a notification (so I can display a message contains the message notificatio ti advise the user). I understand that message is managed by the application. The question is: ...when my application receive the notification is it possible to start it? Or in other world the application became run when receive the notification or it simple became active only to manage the message and at the end of notification management the app return to sleep? The main application windows is opened on the device ? Many thanks in advance Lukenukem Ciao

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  • What is the proper way to check the previous value of a field before saving an object? (Using Django

    - by anonymous coward
    I have a Django Model with updated_by and an approved_by fields, both are ForeignKey fields to the built-in (auth) User models. I am aware that with updated_by, it's easy enough to simply over-ride the .save() method on the Model, and shove the request.user in that field before saving. However, for approved_by, this field should only ever be filled in when a related field (date_approved) is first filled in. I'm somewhat certain that I can check this logically, and fill in the field if the previous value was empty. What is the proper way to check the previous value of a field before saving an object? I do not anticipate that date_approved will ever be changed or updated, nor should there be any reason to ever update the approved_by entry. UPDATE: Regarding forms/validation, I should have mentioned that none of the fields in question are seen by or editable by users of the site. If I have misunderstood, I'm sorry, but I'm not sure how forms and validation apply to my question.

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  • why doesnt' nhibernate support this "exists in list" syntax ??

    - by ooo
    i have the following query and its failing in Nhibernate 3 LINQ witha a "Non supported" exception. Its similar to this question but this question was asked over a year ago so i am positive that the answer is out of date. My DB tables are: VacationRequest (id, personId) VacationRequestDate (id, vacationRequestId) Person (id, FirstName, LastName) My Entities are: VacationRequest (Person, IList) VacationRequestDate (VacationRequest, Date) Here is the query that is getting a "Non supported" Exception Session.Query<VacationRequestDate>() .Where(r => people .Contains(r.VacationRequest.Person, new PersonComparer())) .Fetch(r=>r.VacationRequest) .ToList(); is there a better way to write this that would be supported in Nhibernate? fyi . .the PersonComparer just compared person.Id

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  • Which class will be instantiated

    - by Michael
    Say I have 2 subclasses from UIViewController, class A and class B. In Main nib file an object is representing class A and it is set to load file from Secondary nib file. The owner of Secondary nib is of class B. The question is - from which class an object in Main nib file will be instanciated once the nib files unarchived in the memory? The reason this question arised is that I have to take care myself if such reference to external NIB file present, to ensure that the first nib's object and second nib's owner is same. Please correct me if my statement is wrong.

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  • Tiling rectangles seamlessly in WPF while maintaing subpixel accuracy?

    - by Jens
    I have had the problem described in the question Tiling rectangles seamlessly in WPF, but am not really happy with the answers given there. I am painting a bar chart by painting lots of rectangles right next to each other. Depending on the scale of the canvas containing them, there are small gaps visible between some of them as a result from sub-pixel rendering. I learned from the above question how to make my rectangles fit with the screen pixels, removing that effect. Unfortunately, my chart may display way more bars than there are pixels. Apart from the tiny gaps (which manifest as a periodic change in color saturation), this works well. If I snap each bar with the screen pixels, most of the bars vanish, though, so I am looking for another solution. Thanks in advance!

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  • how to create english language dictionary application with python (django)?

    - by sintaloo
    Hi All, I would like to create an online dictionary application by using python (or with django). It will be similar to http://dictionary.reference.com/. My question is (1) Are there any existing open source python package or modules or application which implements this functionality that I can use or study from? (2) If the answer to the first question is NO. which algorithm should I follow to create such web application? Can I simply use the python built-in dictionary object for this job? so that the dictionary object's key will be the english word and the value will be the explanation. is this OK in term of performance? OR Do I have to create my own Tree Object to speed up the search? or any existing package which handles this job properly? Thank you very much.

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