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  • Avoid loading unnecessary data from db into objects (web pages)

    - by GmGr
    Really newbie question coming up. Is there a standard (or good) way to deal with not needing all of the information that a database table contains loaded into every associated object. I'm thinking in the context of web pages where you're only going to use the objects to build a single page rather than an application with longer lived objects. For example, lets say you have an Article table containing id, title, author, date, summary and fullContents fields. You don't need the fullContents to be loaded into the associated objects if you're just showing a page containing a list of articles with their summaries. On the other hand if you're displaying a specific article you might want every field loaded for that one article and maybe just the titles for the other articles (e.g. for display in a recent articles sidebar). Some techniques I can think of: Don't worry about it, just load everything from the database every time. Have several different, possibly inherited, classes for each table and create the appropriate one for the situation (e.g. SummaryArticle, FullArticle). Use one class but set unused properties to null at creation if that field is not needed and be careful. Give the objects access to the database so they can load some fields on demand. Something else? All of the above seem to have fairly major disadvantages. I'm fairly new to programming, very new to OOP and totally new to databases so I might be completely missing the obvious answer here. :)

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  • Comparing two Objects which implement the same interface for equality / equivalence - Design help

    - by gav
    Hi All, I have an interface and two objects implementing that interface, massively simplied; public interface MyInterface { public int getId(); public int getName(); ... } public class A implements MyInterface { ... } public class B implements MyInterface { ... } We are migrating from using one implementation to the other but I need to check that the objects of type B that are generated are equivalent to those of type A. Specifically I mean that for all of the interface methods an object of Type A and Type B will return the same value (I'm just checking my code for generating this objects is correct). How would you go about this? Map<String, MyInterface> oldGeneratedObjects = getOldGeneratedObjects(); Map<String, MyInterface> newGeneratedObjects = getNewGeneratedObjects(); // TODO: Establish that for each Key the Values in the two maps return equivalent values. I'm looking for good coding practices and style here. I appreciate that I could just iterate through one key set pulling out both objects which should be equivalent and then just call all the methods and compare, I'm just thinking there may be a cleaner, more extensible way and I'm interested to learn what options there might be. Would it be appropriate / possible / advised to override equals or implement Comparable? Thanks in advance, Gavin

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  • What is the best way to find a processed memory allocations in terms of C# objects

    - by Shantaram
    I have written various C# console based applications, some of them long running some not, which can over time have a large memory foot print. When looking at the windows perofrmance monitor via the task manager, the same question keeps cropping up in my mind; how do I get a break down of the number objects by type that are contributing to this footprint; and which of those are f-reachable and those which aren't and hence can be collected. On numerous occasions I've performed a code inspection to ensure that I am not unnecessarily holding on objects longer than required and disposing of objects with the using construct. I have also recently looked at employing the CG.Collect method when I have released a large number of objects (for example held in a collection which has just been cleared). However, I am not so sure that this made that much difference, so I threw that code away. I am guessing that there are tools in sysinternals suite than can help to resolve these memory type quiestions but I am not sure which and how to use them. The alternative would be to pay for a third party profiling tool such as JetBrains dotTrace; but I need to make sure that I've explored the free options first before going cap in hand to my manager.

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  • Reference to the Main Form whilst trying to Serialize objects in C#

    - by Paul Matthews
    I have a button on my main form which calls a method to serialize some objects to disk. I am trying to add these objects to an ArrayList and then serialize them using a BinaryFormatter and a FileStream. public void SerializeGAToDisk(string GenAlgName) { // Let's make a list that includes all the objects we // need to store a GA instance ArrayList GAContents = new ArrayList(); GAContents.Add(GenAlgInstances[GenAlgName]); // Structure and info for a GA GAContents.Add(RunningGAs[GenAlgName]); // There may be several running GA's using (FileStream fStream = new FileStream(GenAlgName + ".ga", FileMode.Create, FileAccess.Write, FileShare.None)) { BinaryFormatter binFormat = new BinaryFormatter(); binFormat.Serialize(fStream, GAContents); } } When running the above code I get the following exception: System.Runtime.Serialization.SerializationException was unhandled Message=Type 'WindowsFormsApplication1.Form1' in Assembly 'GeneticAlgApp, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' is not marked as serializable. So that means that somewhere in the objects I'm trying to save there must be a reference to the main form. The only possible references I can see are 3 delegates which all point to methods in the main form code. Do delegates get serialized as well? I can't seem to apply the [NonSerialized] attribute to them. Is there anything else I might be missing? Even better, is there a quick method to find the reference(s) that are causing the problem?

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  • Entity Framework POCO objects

    - by Dan
    I'm struggling with understanding Entity Framework and POCO objects. Here's what I'm trying to achieve. 1) Separate the DAL from the Business Layer by having my business layer use an interface to my DAL. Maybe use Unity to create my context. 2) Use Entity Framework inside my DAL. I have a Domain model with objects that reside in my business layer. I also have a database full of tables that doesn't really represent my domain model. I setup Entity Framework and generated POCO objects by using the ADO.NET POCO Generator extension. This gave me an object for each table in my database. Now I want to be able to say context.GetAll<User>(); and have it return a list of my User objects. The User object is in my business layer. Is that possible? Does that make sense or am I totally off and should start over? I'm guessing I need to use the repository pattern to achieve this, but I'm not sure. Can anyone help?

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  • how do I best create a set of list classes to match my business objects

    - by ken-forslund
    I'm a bit fuzzy on the best way to solve the problem of needing a list for each of my business objects that implements some overridden functions. Here's the setup: I have a baseObject that sets up database, and has its proper Dispose() method All my other business objects inherit from it, and if necessary, override Dispose() Some of these classes also contain arrays (lists) of other objects. So I create a class that holds a List of these. I'm aware I could just use the generic List, but that doesn't let me add extra features like Dispose() so it will loop through and clean up. So if I had objects called User, Project and Schedule, I would create UserList, ProjectList, ScheduleList. In the past, I have simply had these inherit from List< with the appropriate class named and then written the pile of common functions I wanted it to have, like Dispose(). this meant I would verify by hand, that each of these List classes had the same set of methods. Some of these classes had pretty simple versions of these methods that could have been inherited from a base list class. I could write an interface, to force me to ensure that each of my List classes has the same functions, but interfaces don't let me write common base functions that SOME of the lists might override. I had tried to write a baseObjectList that inherited from List, and then make my other Lists inherit from that, but there are issues with that (which is really why I came here). One of which was trying to use the Find() method with a predicate. I've simplified the problem down to just a discussion of Dispose() method on the list that loops through and disposes its contents, but in reality, I have several other common functions that I want all my lists to have. What's the best practice to solve this organizational matter?

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  • Avoiding duplicate objects in Java deserialization

    - by YGL
    I have two lists (list1 and list2) containing references to some objects, where some of the list entries may point to the same object. Then, for various reasons, I am serializing these lists to two separate files. Finally, when I deserialize the lists, I would like to ensure that I am not re-creating more objects than needed. In other words, it should still be possible for some entry of List1 to point to the same object as some entry in List2. MyObject obj = new MyObject(); List<MyObject> list1 = new ArrayList<MyObject>(); List<MyObject> list2 = new ArrayList<MyObject>(); list1.add(obj); list2.add(obj); // serialize to file1.ser ObjectOutputStream oos = new ObjectOutputStream(...); oos.writeObject(list1); oos.close(); // serialize to file2.ser oos = new ObjectOutputStream(...); oos.writeObject(list2); oos.close(); I think that sections 3.4 and A.2 of the spec say that deserialization strictly results in the creation of new objects, but I'm not sure. If so, some possible solutions might involve: Implementing equals() and hashCode() and checking references manually. Creating a "container class" to hold everything and then serializing the container class. Is there an easy way to ensure that objects are not duplicated upon deserialization? Thanks.

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  • Inversion of control domain objects construction problem

    - by Andrey
    Hello! As I understand IoC-container is helpful in creation of application-level objects like services and factories. But domain-level objects should be created manually. Spring's manual tells us: "Typically one does not configure fine-grained domain objects in the container, because it is usually the responsibility of DAOs and business logic to create/load domain objects." Well. But what if my domain "fine-grained" object depends on some application-level object. For example I have an UserViewer(User user, UserConstants constants) class. There user is domain object which cannot be injected, but UserViewer also needs UserConstants which is high-level object injected by IoC-container. I want to inject UserConstants from the IoC-container, but I also need a transient runtime parameter User here. What is wrong with the design? Thanks in advance! UPDATE It seems I was not precise enough with my question. What I really need is an example how to do this: create instance of class UserViewer(User user, UserService service), where user is passed as the parameter and service is injected from IoC. If I inject UserViewer viewer then how do I pass user to it? If I create UserViewer viewer manually then how do I pass service to it?

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  • WCF data services - Limiting related objects returned based on critera

    - by Mike Morley
    I have an object graph consisting of a base employee object, and a set of related message objects. I am able to return the employee objects based on search criteria on the employee properties (eg team) etc. However, if I expand on the messages, I get the full collection of messages back. I would like to be able to either take the top n messages (i.e. restrict to 10 most recent) or ideally use a date range on the message objects to limit how many are brought back. So far I have not been able to figure out a way of doing this: I get an error if I attempt to filter on properties on the message (&$filter=employee/message/StartDate gives an error "No property 'StartDate' exists in type 'System.Data.Objects.DataClasses.EntityCollection`1). Attempting to use Top on the message related object doesn't work either. I have also tried using a WebGet extension that takes a string list of employee IDs. That works until the list gets too long, and then fails due to the URL getting too long (it might be possible to setup a paging mechanism on this approach)... Unfortunately the UI control I am using requires the data to be in a fairly specific hierarchical shape, so I can't easily come at this from starting on the message side and working backwards. Outside of making multiple calls does anyone know of a method to accomplish this with wcf data services? Thanks! M.

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  • Where to place interactive objects in JavaScript?

    - by Chris
    I'm creating a web based application (i.e. JavaScript with jQuery and lots of SVG) where the user interacts with "objects" on the screen (think of DIVs that can be draged around, resized and connected by arraows - like a vector drawing programm or a graphical programming language). As each "object" contains individual information but is allways belonging to a "class" of elements it's obvious that this application should be programmed by using an OOP approach. But where do I store the "objects" best? Should I create a global structure ("registry") with all (JS native) objects and tell them "draw yourself on the DOM"? Or should I avoid such a structure and think of the (relevant) DOM nodes as my objects and attach the relevant data as .data() to them? The first approach is very MVC - but I guess the attachment of all the event handlers will be non trivial. The second approach will handle the events in a trivial way and it doesn't create a duplicate structure, but I guess the usual OO stuff (like methods) will be more complex. What do you recomend? I think the answer will be JavaScript and SVG specific as "usual" programming languages don't have such a highly organized output "canvas".

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  • How to synchronize access to many objects

    - by vividos
    I have a thread pool with some threads (e.g. as many as number of cores) that work on many objects, say thousands of objects. Normally I would give each object a mutex to protect access to its internals, lock it when I'm doing work, then release it. When two threads would try to access the same object, one of the threads has to wait. Now I want to save some resources and be scalable, as there may be thousands of objects, and still only a hand full of threads. I'm thinking about a class design where the thread has some sort of mutex or lock object, and assigns the lock to the object when the object should be accessed. This would save resources, as I only have as much lock objects as I have threads. Now comes the programming part, where I want to transfer this design into code, but don't know quite where to start. I'm programming in C++ and want to use Boost classes where possible, but self written classes that handle these special requirements are ok. How would I implement this? My first idea was to have a boost::mutex object per thread, and each object has a boost::shared_ptr that initially is unset (or NULL). Now when I want to access the object, I lock it by creating a scoped_lock object and assign it to the shared_ptr. When the shared_ptr is already set, I wait on the present lock. This idea sounds like a heap full of race conditions, so I sort of abandoned it. Is there another way to accomplish this design? A completely different way?

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  • UIDs for data objects in MySQL

    - by Callash
    Hi there, I am using C++ and MySQL. I have data objects I want to persist to the database. They need to have a unique ID for identification purposes. The question is, how to get this unique ID? Here is what I came up with: 1) Use the auto_increment feature of MySQL. But how to get the ID then? I am aware that MySQL offers this "SELECT LAST_INSERT_ID()" feature, but that would be a race condition, as two objects could be inserted quite fast after each other. Also, there is nothing else that makes the objects discernable. Two objects could be created pretty much at the same time with exactly the same data. 2) Generate the UID on the C++ side. No dice, either. There are multiple programs that will write to and read from the database, who do not know of each other. 3) Insert with MAX(uid)+1 as the uid value. But then, I basically have the same problem as in 1), because we still have the race condition. Now I am stumped. I am assuming that this problem must be something other people ran into as well, but so far, I did not find any answers. Any ideas?

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  • Best CPUs for speeding up compiling times of C++ w/ DistGCC

    - by Jay
    I'm putting together a distributed build farm with DistGCC to speed up our teams compile times and just looking for thoughts on which processors to use in the hosts. Are we going to get a noticeable decrease in time using 8 cores vs. 4-hyperthreaded cores? Big difference in time between i7 and Xeon? etc, etc. Just need advice from people who've put together kick-a build clusters. We've got a majority of the normal things to speed up builds in place (pre-compiled headers, ccache, local gigabit connections between them, tons of ram, etc) so please just give advice on the best processor to use. And money is a factor, but anythings doable if the performance increase is noticeable. Thanks. Jay EDIT: Although any advice IS welcome, please refrain from "Do this first" posts as we're not planning on skimping on things like SSD, maxed out RAM, etc. My personal system is a iMac Quad-core i5 with 8GB of RAM. When I build our project locally, my processor floats around 99-100% a majority of the time, which makes me assume it is a bottleneck, even if you made everything else faster. My ram on the other hand doesn't even get close to maxing out. It's also worth noting that I did research this, however every discussion I could find was primarily for gaming machines, which is obviously a different beast in usage. These machines won't even have monitors or anything but integrated graphics since they have one purpose: Build freakin fast. (hopefully)

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  • Best CPUs for speeding up compiling times of C++ w/ DistGCC

    - by Jay
    I'm putting together a distributed build farm with DistGCC to speed up our teams compile times and just looking for thoughts on which processors to use in the hosts. Are we going to get a noticeable decrease in time using 8 cores vs. 4-hyperthreaded cores? Big difference in time between i7 and Xeon? etc, etc. Just need advice from people who've put together kick-a build clusters. We've got a majority of the normal things to speed up builds in place (pre-compiled headers, ccache, local gigabit connections between them, tons of ram, etc) so please just give advice on the best processor to use. And money is a factor, but anythings doable if the performance increase is noticeable. Thanks. Jay EDIT: Although any advice IS welcome, please refrain from "Do this first" posts as we're not planning on skimping on things like SSD, maxed out RAM, etc. My personal system is a iMac Quad-core i5 with 8GB of RAM. When I build our project locally, my processor floats around 99-100% a majority of the time, which makes me assume it is a bottleneck, even if you made everything else faster. My ram on the other hand doesn't even get close to maxing out. It's also worth noting that I did research this, however every discussion I could find was primarily for gaming machines, which is obviously a different beast in usage. These machines won't even have monitors or anything but integrated graphics since they have one purpose: Build freakin fast. (hopefully)

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  • Best CPUs for speeding up compiling times of C++ w/ DistGCC

    - by Jay
    I'm putting together a distributed build farm with DistGCC to speed up our teams compile times and just looking for thoughts on which processors to use in the hosts. Are we going to get a noticeable decrease in time using 8 cores vs. 4-hyperthreaded cores? Big difference in time between i7 and Xeon? etc, etc. Just need advice from people who've put together kick-a build clusters. We've got a majority of the normal things to speed up builds in place (pre-compiled headers, ccache, local gigabit connections between them, tons of ram, etc) so please just give advice on the best processor to use. And money is a factor, but anythings doable if the performance increase is noticeable. Thanks. Jay EDIT: Although any advice IS welcome, please refrain from "Do this first" posts as we're not planning on skimping on things like SSD, maxed out RAM, etc. My personal system is a iMac Quad-core i5 with 8GB of RAM. When I build our project locally, my processor floats around 99-100% a majority of the time, which makes me assume it is a bottleneck, even if you made everything else faster. My ram on the other hand doesn't even get close to maxing out. It's also worth noting that I did research this, however every discussion I could find was primarily for gaming machines, which is obviously a different beast in usage. These machines won't even have monitors or anything but integrated graphics since they have one purpose: Build freakin fast. (hopefully)

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  • Clustering filesystem for small files

    - by viraptor
    Hi, I'm looking for a distributed filesystem which I could use for storing lots of small files (<1MB usually). What I want to get is: 2 servers which have the fs mounted themselves and mirror the data locking support (among reachable nodes) some kind of best-effort automatic resynchronisation after one node goes down and comes back again What I mean by the resync is that, I'm ok with both servers doing read/write operations even if they split-brain. I'm also ok if a local process obtains a lock if the other host is not reachable. From the resync I expect only a file-level consistent view after a while - that is - if file x is modified on both nodes during a split-brain, I don't really care which one is available after they join again, as long as it's full file, not one block coming from node1 and another block from node2. Is there a solution like that out there? I see that gluster has some problems with file locks (even in 3.1). I also noticed that OCFS2 will panic if both nodes split-brain. What other filesystem would allow me to do what I want?

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  • Distributing processing for an application that wasn't designed with that in mind

    - by Tim
    We've got the application at work that just sits and does a whole bunch of iterative processing on some data files to perform some simulations. This is done by an "old" Win32 application that isn't multi-processor aware, so new(ish) computers and workstations are mostly sitting idle running this application. However, since it's installed by a typical Windows Install Shield installer, I can't seem to install and run multiple copies of the application. The work can be split up manually before processing, enabling the work to be distributed across multiple machines, but we still can't take advantage of multiple core CPUs. The results can be joined back together after processing to make a complete simulation. Is there a product out there that would let me "compartmentalize" an installation (or 4) so I can take advantage of a multi-core CPU? I had thought of using MS Softgrid, but I believe that still depends on a remote server to do the heavy lifting (though please correct me if I'm wrong). Furthermore, is there a way I can distribute the workload off the one machine? So an input could be split into 50 chunks, handed out to 50 machines, and worked on? All without really changing the initial application? In a perfect world, I'd get the application to take advantage of a DesktopGrid (BOINC), but like most "mission critical corporate applications", the need is there, but the money is not. Thank you in advance (and sorry if this isn't appropriate for serverfault).

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  • Nagios DNX plugins

    - by danneh3826
    I'm toying with the idea of multiple Nagios instances setup to monitor our infrastructure. I've looked at all the various methods of distributed Nagios checks, and I think DNX comes out the closest. DNX handles failure of worker nodes, that's fine. What happens if the main DNX server fails though? Is there a way to replicate the server too? I'm using AWS EC2 primarily, so I can utilise Elastic Load Balancing for the web UI, but I need to be able to handle the AZ where the monitoring server is to fail over, and essentially for a second to pick up the checking load (active/passive, active/active, so long as it doesn't fail completely) The other thing I'm trying to solve is an issue with routing. What I'd like is to have multiple nodes report a fault before Nagios confirms it as critical. Not the NRPE checks, as they're pretty self explanitory, but things more like check_ping. I often have routing issues out of AWS to certain datacenters, so Nagios can often report bad/no ping/timeout as a critical issue, even though the machine in question is working fine. Would it be possible to have a setup where a worker complains a service check is critical, and have a second worker node (positioned in another datacenter/AZ) also report the service as critical before the Nagios central server issues a critical alert? I realise I might be asking a bit much (how far down the line do you go setting up failover systems before it starts to get ridiculous), however surely someone must have thought of this scenario when developing DNX?

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  • How to distribute multiple executions of an app across many machines

    - by Salec
    I've got a simulation app (64-bit windows) that runs without any user interaction. This app gathers information and pushes it to a remote MS SQL Server. What I'd like to do is execute this simulation as many times as I can on multiple machines after our nightly build has finished and it has passed the test suite. If possible I'd love to have the ability to configure it to stop after x total runs or if the entire batch has taken over y hours. I've tried using Visual Studio's built in test framework since we already have a test lab set up with multiple agents. I created a single unit test that simply runs the simulation then I created an ordered test and added that single test multiple times (from what I gather, this is the only way to execute the same unit test more than once). I found that ordered tests are only run on a single agent and not distributed which is very limiting. We use TeamCity to perform our nightly builds and I suspect it's possible to implement this on top of that, but I'm fairly new to TeamCity. We also have Jenkins and Bamboo available and I'm open to any other software that would get the job done presuming it runs on a 64-bit Windows OS. Any suggestions?

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  • Suggestion on algorithm to distribute objects of different value

    - by Unknown
    Hello, I have the following problem: Given N objects of different values (N < 30, and the values are multiple of a "k" constant, i.e. k, 2k, 3k, 4k, 6k, 8k, 12k, 16k, 24k and 32k), I need an algorithm that will distribute all items to M players (M <= 6) in such a way that the total value of the objects each player gets is as even as possible (in other words, I want to distribute all objects to all players in the fairest way possible). I don't need (pseudo)code to solve this (also, this is not a homework :) ), but I'll appreciate any ideas or links to algorithms that could solve this. Thanks!

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  • Problem with fetching dictionary objects in array from plist iphone sdk

    - by neha
    Hi all, What is the datatype you use to fetch items whose type is dictionary in plist i.e. nsmutabledictionary or nsdictionary? Because I'm using following code to retrieve dictionary objects from an array of dictionaries in plist. NSMutableDictionary *_myDict = [contentArray objectAtIndex:0]; NSLog(@"MYDICT : %@",_myDict); NSString *myKey = (NSString *)[_myDict valueForKey:@"Contents"] ; [[cell lblFeed] setText:[NSString stringWithFormat:@"%@",myKey]]; Here, on first line it's showing me objc_msgsend. ContentArray is an nsarray and it's contents are showing 2 objects that are there in plist. In plist they are dictionary objects. Then why this error? Can anybody please help? Thanx in advance.

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  • Cocoa - Enumerate mutable array, removing objects

    - by Ward
    Hey there, I have a mutable array that contains mutable dictionaries with strings for the keys latitude, longitude and id. Some of the latitude and longitude values are the same and I want to remove the duplicates from the array so I only have one object per location. I can enumerate my array and using a second enumeration review each object to find objects that have different ids, but the same latitude and longitude, but if I try to remove the object, I'm muting the array during enumeration. Is there any way to remove objects from an array while enumerating so I only enumerate the current set of objects as the array is updated? Hope this question makes sense. Thanks, Howie

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  • Flex AdvancedDataGrid with Grouping, how do I get objects to appear under first GroupingField if the

    - by shadenite
    I am using an AdvancedDataGrid with two GroupingFields. The dataProvider has a list of objects with these two field values, but occasionally the second field value can be null. When it loads, the AdvancedDataGrid UI has a root folder (first GroupingField) and some additional subfolders (second GroupingField). This is all good. However, the objects with a null value for the second GroupingField, just get placed in a subfolder with no label. I want the objects with a null second GroupingField value to appear as leaf nodes beneath the root folder (first GroupingField) minus the blank subfolder. A good way to picture this would be a file explorer. Is there a good way to do this? Make the folder icon disappear maybe after expanding this node through actionscript? ParentFolder SubFolder Leaf Object Leaf Object SubFolder Leaf Object Leaf Object Leaf Object

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  • How to remove objects from an Enumerable collection in a loop

    - by johnc
    Duplicate Modifying A Collection While Iterating Through It Has anyone a nice pattern to allow me to get around the inability to remove objects while I loop through an enumerable collection (eg, an IList or KeyValuePairs in a dictionary) For example, the following fails, as it modifies the List being enumerated over during the foreach foreach (MyObject myObject in MyListOfMyObjects) { if (condition) MyListOfMyObjects.Remove(myObject); } In the past I have used two methods. I have replaced the foreach with a reversed for loop (so as not to change the any indexes I am looping over if I remove an object). I have also tried storing a new collection of objects to remove within to loop, then looping through that collection and removed the objects from the original collection. These work fine, but neither feels nice, and I was wondering if anyone has come up with a more elegant solution to the issue

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