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  • How to load entities into readonly collections using the entity framework

    - by Anton P
    I have a POCO domain model which is wired up to the entity framework using the new ObjectContext class. public class Product { private ICollection<Photo> _photos; public Product() { _photos = new Collection<Photo>(); } public int Id { get; set; } public string Name { get; set; } public virtual IEnumerable<Photo> Photos { get { return _photos; } } public void AddPhoto(Photo photo) { //Some biz logic //... _photos.Add(photo); } } In the above example i have set the Photos collection type to IEnumerable as this will make it read only. The only way to add/remove photos is through the public methods. The problem with this is that the Entity Framework cannot load the Photo entities into the IEnumerable collection as it's not of type ICollection. By changing the type to ICollection will allow callers to call the Add mentod on the collection itself which is not good. What are my options?

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  • Java: Finding objects in collections.

    - by Jake
    This problem occurs over and over. I have some complicated object, such as a Cat, which has many properties, such as age, favorite cat food, and so forth. A bunch of Cats are stored in a Java Collection, and I need to find all the Cats that are aged 3, or those whose favorite cat food is Whiskas. Surely, I can write a custom method that finds those Cats with a specific property, but this gets cumbersome with many properties; is there some generic way of doing this?

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  • Collections removeAll method

    - by srinannapa
    I would like to know if something like below is possible , list<**MyObject**>.**removeAll**(list<**String**>) I hope the context is understandable. The list<MyObject : is a ArrayList<MyObject The list<String : is a ArrayList<String I know this can be achieved by overriding equals method in MyObject class. I would like to know if any other choice is prsent. Thanks,Srinivas N

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  • google collections ordering on map values

    - by chris-gr
    I would like to order a map based on the values. Function<Map.Entry<A, Double>, Double> getSimFunction = new Function<Map.Entry<A, Double>, Double>() { public Double apply(Map.Entry<A, Double> entry) { return entry.getValue(); } }; final Ordering<Map.Entry<A, Double>> entryOrdering = Ordering.natural().onResultOf(getSimFunction); ImmutableSortedMap.orderedBy(entryOrdering).putAll(....).build(); How can I create a new sortedMap based on the ordering results or a sortedset based on the map.keyset()?

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  • AutoMapping Custom Collections with FluentNHibernate

    - by ScottBelchak
    I am retrofitting a very large application to use NHibernate as it's data access strategy. Everything is going well with AutoMapping. Luckily when the domain layer was built, we used a code generator. The main issue that I am running into now is that every collection is hidden behind a custom class that derives from List<. For example public class League { public OwnerList owners {get;set;} } public class OwnerList : AppList<Owner> { } public class AppList<T> : List<T> { } What kind of Convention do I have to write to get this done?

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  • C++ stl collections or linked lists

    - by Lucas
    I'm developing a OpenGL based simulation in C++. I'm optmizing my code now and i see throughout the code the frequently use of std:list and std:vector. What is the more performatic: to continue using C++ stl data structs or a pointer based linked list? The main operation that involve std::list and std::vector is open a iterator and loop through all items in the data structs and apply some processing

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  • scala 2.8 implict java collections conversions

    - by nablik
    I have problem with JavaConversions with 2.8 beta: import scala.collection.JavaConversions._ class Utils(dbFile : File, sep: String) extends IUtils { (...) def getFeatures() : java.util.List[String] = csv.attributes.toList } And then exception: [INFO] Utils.scala:20: error: type mismatch; [INFO] found : List[String] [INFO] required: java.util.List[String] [INFO] def getFeatures() : java.util.List[String] = csv.attributes.toList [INFO]

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  • WPF: how to define collections for use in xaml

    - by Aran Mulholland
    I want to define something like this <myCustomControl> <myCustomControl.Images> <Image Source="{StaticResource LockedIcon16}" /> <Image Source="{StaticResource UnlockedIcon16}"/> <myCustomControl.Images> <myCustomControl/> what property definitions do i need to get that collection (Images) happening?

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  • C Language Standard Collections Where Are They?

    - by flaxeater
    I have committed to learning C now, I'm good with Python/PHP/Bash but I've decided I'm limited by not being fluent in C. However I cannot imagine working in a language without lists and hashes, maybe I'm just jumping a gun, but surely there are 'standard' collection libraries. I do not see any in the GNU standard lib though, any suggestions?

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  • Threading and iterating through changing collections

    - by adamjellyit
    In C# (console app) I want to hold a collection of objects. All objects are of same type. I want to iterate through the collection calling a method on each object. And then repeat the process continuously. However during iteration objects can be added or removed from the list. (The objects themselves will not be destroyed .. just removed from the list). Not sure what would happen with a foreach loop .. or other similar method. This has to have been done 1000 times before .. can you recommend a solid approach?

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  • Updating the collections of entities with NHibernate the correct way

    - by karel_evzen
    A simple question regarding how NHibernate works: I have a parent entity that has a collection of other child entities. Those child entities have a reference to the parent entity they belong to. Now I want to implement an Add method to the parent entity that would add a child to it. Should that Add method only add the child to its new parents collection, or should it also update the parent reference of the child or should it also remove the added entity from its previous parents collection? Do I have to do all these things in that method or will NHibernate do something for me? Thanks.

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  • Problem with underscore(_) in Collections.binarySearch (Java)

    - by Alex Cheng
    Hi all. Problem: I am using Java Tutorials™ sourcecode for this. This is the source code. I tried this: --following with another section of sorted words-- words.add("count"); words.add("cvs"); words.add("dce"); words.add("depth"); --following with another section of sorted words-- and it works perfectly. However when I use this: --just a section of sorted words-- words.add("count"); words.add("cvs"); words.add("dce_iface"); words.add("dce_opnum"); words.add("dce_stub_data"); words.add("depth"); --following with another section of sorted words-- It does show dce_iface when I type dce, but when I type _ then following with o or s it shows me something else like dce_offset where the offset comes from words.add("fragoffset"); somewhere in the list. What can I do to solve this problem? Thank you in advance.

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  • Best Java thread-safe locking mechanism for collections?

    - by Simon
    What would be the least-slow thread-safe mechanism for controlling multiple accesses to a collection in Java? I am adding objects to the top of a collection and i am very unsure what would be the best performing collection. Would it be a vector or a queue? I originally thought an ArrayList would be fast but i ran some experiments and it was very slow. EDIT: In my insertion testing a Vector delared using volatile seems to be the fastest?

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  • Need a Holistic view of your Concurrent Processing? Choose CP Analyzer

    - by user793044
    The Concurrent Processing Analyzer is a Self-Service Health-Check script which reviews the overall Concurrent Processing Footprint, analyzes the current configurations and settings for the environment providing feedback and recommendations on Best Practices. This is a non-invasive script which provides recommended actions to be performed on the instance it was run on.  For production instances, always apply any changes to a recent clone to ensure an expected outcome. Benefits include: E-Business Applications Concurrent Processing Analyzer Overview E-Business Applications Concurrent Request Analysis E-Business Applications Concurrent Manager Analysis Identifies Concurrent System Setup and configurations Identifies and recommends Concurrent Best Practices Easy to add Tool for regular Concurrent Maintenance Execute Analysis anytime to compare trending from past outputs Go to Doc ID 1411723.1 for more details and script download. Feedback welcome!

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  • Web framework able to handle many concurrent users [closed]

    - by Jonas
    Social networking sites needs to handle many concurrent users e.g. for chat functionality. What web frameworks scales well and are able to handle more than 10.000 concurrent users connected with Comet or WebSockets. The server is a Linux VPS with limited memory, e.g. 1GB-8GB. I have been looking for some Java frameworks but they consume much memory per connection. So I'm looking for other alternatives too. Are there any good frameworks that are able to handle more than 10.000 concurrent users with limited memory resources?

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  • Update a file inside zip with -u

    - by user577732
    Alright so i have a zip file called data.zip on my desktop. Inside test.zip is another folder called res and inside res is a file called info.txt I have used the zip -u command before to move a file inside the zip but only to the root of the zip i want to move a new version of info.txt from my desktop to the res folder of data.zip i need it for part of a script i'm working on. How can i do this or will the -u function only work for the root? Thank you for any help on how i can accomplish this

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  • Find messages[from-to]

    - by Alfred
    I would like to return all messages from certain key to a certain key. The class should be thread-safe and old keys should be able to be deleted say for example after 30 seconds. I was thinking of using a concurrentskiplistset or concurrentskiplist map. Also I was thinking of deleting the items from inside a newSingleThreadScheduledExecutor. I would like to know how you would implement this or maybe use a library?

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  • Tips on debugging collections

    - by Vincent Grondin
    The "Quick Watch" feature of Visual Studio is an awesome tool when debugging your stuff...  I use it all the time and quite often I end up exploring hashtables or lists of all sorts...  One thing I hate is when I have to explore Collections...  Good god did I lose time trying to find the inner member that contains my stuff when exploring collections...  Most collections have the inside member that you can search for and find and explore to see the list of things you wanted to look at.  Something in the likes of this.    I've known a little trick for a while now and I give it to everyone I end up debugging something with so I figured that probably not many people know about this...  Here's the tip...  Send the collection into an ArrayList in the QuickWatch window!  Yes, you heard me right, just type    new ArrayList(yourcollectionhere) in my case:    new ArrayList(this.Controls) in the expresion textbox and here's the result when you hit reevaluate! Pretty neat trick to make your debugging experience less of a pain when dealing with collections...    Happy debugging all !

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  • How to sort TBB concurrent_vector or concurrent_queue?

    - by Jackie
    Now I have a solver in that I need to keep a set of self-defined data type objects in a concurrent_vector or queue. It has to be concurrent because the objects come from different threads.With this concurrent container, I hope to sort these objects, eliminate duplicates and send them back when other threads need them. However, I know TBB offers concurrent_vector and concurrent_queue which can be read and written concurrently from different threads. But how to sort the objects inside a container? Does everyone know how to do that? Thanks.

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  • C#: System.Collections.Concurrent.ConcurrentQueue vs. Queue

    - by James Michael Hare
    I love new toys, so of course when .NET 4.0 came out I felt like the proverbial kid in the candy store!  Now, some people get all excited about the IDE and it’s new features or about changes to WPF and Silver Light and yes, those are all very fine and grand.  But me, I get all excited about things that tend to affect my life on the backside of development.  That’s why when I heard there were going to be concurrent container implementations in the latest version of .NET I was salivating like Pavlov’s dog at the dinner bell. They seem so simple, really, that one could easily overlook them.  Essentially they are implementations of containers (many that mirror the generic collections, others are new) that have either been optimized with very efficient, limited, or no locking but are still completely thread safe -- and I just had to see what kind of an improvement that would translate into. Since part of my job as a solutions architect here where I work is to help design, develop, and maintain the systems that process tons of requests each second, the thought of extremely efficient thread-safe containers was extremely appealing.  Of course, they also rolled out a whole parallel development framework which I won’t get into in this post but will cover bits and pieces of as time goes by. This time, I was mainly curious as to how well these new concurrent containers would perform compared to areas in our code where we manually synchronize them using lock or some other mechanism.  So I set about to run a processing test with a series of producers and consumers that would be either processing a traditional System.Collections.Generic.Queue or a System.Collection.Concurrent.ConcurrentQueue. Now, I wanted to keep the code as common as possible to make sure that the only variance was the container, so I created a test Producer and a test Consumer.  The test Producer takes an Action<string> delegate which is responsible for taking a string and placing it on whichever queue we’re testing in a thread-safe manner: 1: internal class Producer 2: { 3: public int Iterations { get; set; } 4: public Action<string> ProduceDelegate { get; set; } 5: 6: public void Produce() 7: { 8: for (int i = 0; i < Iterations; i++) 9: { 10: ProduceDelegate(“Hello”); 11: } 12: } 13: } Then likewise, I created a consumer that took a Func<string> that would read from whichever queue we’re testing and return either the string if data exists or null if not.  Then, if the item doesn’t exist, it will do a 10 ms wait before testing again.  Once all the producers are done and join the main thread, a flag will be set in each of the consumers to tell them once the queue is empty they can shut down since no other data is coming: 1: internal class Consumer 2: { 3: public Func<string> ConsumeDelegate { get; set; } 4: public bool HaltWhenEmpty { get; set; } 5: 6: public void Consume() 7: { 8: bool processing = true; 9: 10: while (processing) 11: { 12: string result = ConsumeDelegate(); 13: 14: if(result == null) 15: { 16: if (HaltWhenEmpty) 17: { 18: processing = false; 19: } 20: else 21: { 22: Thread.Sleep(TimeSpan.FromMilliseconds(10)); 23: } 24: } 25: else 26: { 27: DoWork(); // do something non-trivial so consumers lag behind a bit 28: } 29: } 30: } 31: } Okay, now that we’ve done that, we can launch threads of varying numbers using lambdas for each different method of production/consumption.  First let's look at the lambdas for a typical System.Collections.Generics.Queue with locking: 1: // lambda for putting to typical Queue with locking... 2: var productionDelegate = s => 3: { 4: lock (_mutex) 5: { 6: _mutexQueue.Enqueue(s); 7: } 8: }; 9:  10: // and lambda for typical getting from Queue with locking... 11: var consumptionDelegate = () => 12: { 13: lock (_mutex) 14: { 15: if (_mutexQueue.Count > 0) 16: { 17: return _mutexQueue.Dequeue(); 18: } 19: } 20: return null; 21: }; Nothing new or interesting here.  Just typical locks on an internal object instance.  Now let's look at using a ConcurrentQueue from the System.Collections.Concurrent library: 1: // lambda for putting to a ConcurrentQueue, notice it needs no locking! 2: var productionDelegate = s => 3: { 4: _concurrentQueue.Enqueue(s); 5: }; 6:  7: // lambda for getting from a ConcurrentQueue, once again, no locking required. 8: var consumptionDelegate = () => 9: { 10: string s; 11: return _concurrentQueue.TryDequeue(out s) ? s : null; 12: }; So I pass each of these lambdas and the number of producer and consumers threads to launch and take a look at the timing results.  Basically I’m timing from the time all threads start and begin producing/consuming to the time that all threads rejoin.  I won't bore you with the test code, basically it just launches code that creates the producers and consumers and launches them in their own threads, then waits for them all to rejoin.  The following are the timings from the start of all threads to the Join() on all threads completing.  The producers create 10,000,000 items evenly between themselves and then when all producers are done they trigger the consumers to stop once the queue is empty. These are the results in milliseconds from the ordinary Queue with locking: 1: Consumers Producers 1 2 3 Time (ms) 2: ---------- ---------- ------ ------ ------ --------- 3: 1 1 4284 5153 4226 4554.33 4: 10 10 4044 3831 5010 4295.00 5: 100 100 5497 5378 5612 5495.67 6: 1000 1000 24234 25409 27160 25601.00 And the following are the results in milliseconds from the ConcurrentQueue with no locking necessary: 1: Consumers Producers 1 2 3 Time (ms) 2: ---------- ---------- ------ ------ ------ --------- 3: 1 1 3647 3643 3718 3669.33 4: 10 10 2311 2136 2142 2196.33 5: 100 100 2480 2416 2190 2362.00 6: 1000 1000 7289 6897 7061 7082.33 Note that even though obviously 2000 threads is quite extreme, the concurrent queue actually scales really well, whereas the traditional queue with simple locking scales much more poorly. I love the new concurrent collections, they look so much simpler without littering your code with the locking logic, and they perform much better.  All in all, a great new toy to add to your arsenal of multi-threaded processing!

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  • O' Reilly Deal of the Day 26/Jun/2012 - Developer's Guide to Collections in Microsoft® .NET

    - by TATWORTH
    Today's 50% off Deal of the Day at http://shop.oreilly.com/product/0790145317193.do?code=MSDEAL is Developer's Guide to Collections in Microsoft® .NET "Put .NET collections to work—and manage issues with GUI data binding, threading, data querying, and storage. Led by a data collection expert, you'll gain task-oriented guidance, exercises, and extensive code samples to tackle common problems and improve application performance. This one-stop reference is designed for experienced Microsoft Visual Basic® and C# developers—whether you’re already using collections or just starting out." I am reviewing this book. Here are my initial comments:The code is well illustrated by diagrams. The approach is practical. The code is well commented, however the C# code samples would be better had they been fully Style Cop compliant.I recommend this book to all C# and VB.NET Development teams. I concur with the author who states that the book is not for learning C# or VB.NET, however it is an excellent book for C# or VB.NET developers to extend their knowledge of the Dot Net framework.

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