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  • performance of linq extension method ElementAt

    - by Fabiano
    Hi The MSDN library entry to Enumerable.ElementAt(TSource) Method says "If the type of source implements IList, that implementation is used to obtain the element at the specified index. Otherwise, this method obtains the specified element." Let's say we have following example: ICollection<int> col = new List<int>() { /* fill with items */ }; IList<int> list = new List<int>() { /* fill with items */ }; col.ElementAt(10000000); list.ElementAt(10000000); Is there any difference in execution? or does ElementAt recognize that col also implements IList< although it's only declared as ICollection<? Thanks

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  • Mapping a collection of enums with NHibernate

    - by beaufabry
    Mapping a collection of enums with NHibernate Specifically, using Attributes for the mappings. Currently I have this working mapping the collection as type Int32 and NH seems to take care of it, but it's not exactly ideal. The error I receive is "Unable to determine type" when trying to map the collection as of the type of the enum I am trying to map. I found a post that said to define a class as public class CEnumType : EnumStringType { public CEnumType() : base(MyEnum) { } } and then map the enum as CEnumType, but this gives "CEnumType is not mapped" or something similar. So has anyone got experience doing this? So anyway, just a simple reference code snippet to give an example with [NHibernate.Mapping.Attributes.Class(Table = "OurClass")] public class CClass : CBaseObject { public enum EAction { do_action, do_other_action }; private IList<EAction> m_class_actions = new List<EAction>(); [NHibernate.Mapping.Attributes.Bag(0, Table = "ClassActions", Cascade="all", Fetch = CollectionFetchMode.Select, Lazy = false)] [NHibernate.Mapping.Attributes.Key(1, Column = "Class_ID")] [NHibernate.Mapping.Attributes.Element(2, Column = "EAction", Type = "Int32")] public virtual IList<EAction> Actions { get { return m_class_actions; } set { m_class_actions = value;} } } So, anyone got the correct attributes for me to map this collection of enums as actual enums? It would be really nice if they were stored in the db as strings instead of ints too but it's not completely necessary.

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  • C# Winforms: PropertyGrid not updated when item added to Collection

    - by MysticEarth
    I've got a custom class which can be edited through the PropertyGrid. In that class I've got a custom Collection (with custom PropertyDescriptor and TypeConverter). Items can be added to or removed from the Collection with the default Collection Editor. This all works fine. But - after closing the Collection Editor, the PropertyGrid is not updated. When I manual make a call to Refresh() on the PropertyGrid, the changes are reflected in the PropertyGrid. How can I get the PropertyGrid to automatically refresh when the Collection Editor has been closed? I sought for a solution earlier where I should subclass CollectionEditor (which I can't seem to find). Please help.

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  • NameValueCollection vs Dictionary<string,string>

    - by frankadelic
    Any reason I should use Dictionary<string,string instead of NameValueCollection? (in C# / .NET Framework) Option 1, using NameValueCollection: //enter values: NameValueCollection nvc = new NameValueCollection() { {"key1", "value1"}, {"key2", "value2"}, {"key3", "value3"} }; // retrieve values: foreach(string key in nvc.AllKeys) { string value = nvc[key]; // do something } Option 2, using Dictionary<string,string... //enter values: Dictionary<string, string> dict = new Dictionary<string, string>() { {"key1", "value1"}, {"key2", "value2"}, {"key3", "value3"} }; // retrieve values: foreach (KeyValuePair<string, string> kvp in dict) { string key = kvp.Key; string val = kvp.Value; // do something } For these use cases, is there any advantage to use one versus the other? Any difference in performance, memory use, sort order, etc.?

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  • "Collection was modified..." Issue

    - by Tyler Murry
    Hey guys, I've got a function that checks a list of objects to see if they've been clicked and fires the OnClick events accordingly. I believe the function is working correctly, however I'm having an issue: When I hook onto one of the OnClick events and remove and insert the element into a different position in the list (typical functionality for this program), I get the "Collection was modified..." error. I believe I understand what is going on: The function cycles through each object firing OnClick events where necessary An event is fired and the object changes places in the list per the hooked function An exception is thrown for modifying the collection while iterating through it My question is, how to do I allow the function to iterate through all the objects, fire the necessary events at the proper time and still give the user the option of manipulating the object's position in the list? Thanks, Tyler

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  • Returning IEnumerable from an indexer, bad practice?

    - by fearofawhackplanet
    If I had a CarsDataStore representing a table something like: Cars -------------- Ford | Fiesta Ford | Escort Ford | Orion Fiat | Uno Fiat | Panda Then I could do IEnumerable<Cars> fords = CarsDataStore["Ford"]; Is this a bad idea? It's iconsistent with the other datastore objects in my api (which all have a single column PK indexer), and I'm guessing most people don't expect an indexer to return a collection in this situation.

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  • Bind a Java Collection to xQuery sequence from xQuery

    - by jtzero
    declare function Error:toString($this as javaObject) as xs:string external; the previous binds a return String() to xs:string. is it possible to return a collection and bind it to an xQuery Sequence, say the following declare function Error:toList($this as javaObject) as squenceType external; so that it can be run through a flwr?

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  • Language Tricks to Shorten My Java Code?

    - by yar
    I am currently rediscovering Java (working with Ruby a lot recently), and I love the compilation-time checking of everything. It makes refactoring so easy. However, I miss playing fast-and-loose with types to do an each loop. This is my worst code. Is this as short as it can be? I have a collection called looperTracks, which has instances that implement Looper. I don't want to modify that collection, but I want to iterate through its members PLUS the this (which also implements Looper). List<Looper> allLoopers = new ArrayList<Looper>(looperTracks.length + 1); for (LooperTrack track : looperTracks) { allLoopers.add(track); } allLoopers.add(this); for (Looper looper : allLoopers) { // Finally! I have a looper I'm particularly concerned about any features that are new to Java from 1.5 on that I may have missed. For this question I am not asking about JRuby nor Groovy, though I know that they would work for this. Edit: Sorry (too much Ruby!)... looperTracks is of type LooperTrack[] and LooperTrack implements Looper.

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  • ASP.NET MVC2: Can you get ModelMetadata.ContainerType from within a collection?

    - by CodeSponge
    I'm trying to call DisplayFor and DisplayForModel to iterate an IEnumerable< with various element types from within a view. I have Templates defined for each element/Model type. What I would like to do is check the ViewData.ModelMetadata.ContainerType from within the Template so that Template can determine if it was called as part of a collection. A simple example: Index1.aspx: To render a collection of Foos. <%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<IEnumerable<Foo>>" %> <asp:Content ContentPlaceHolderID="MainPlaceHolder" runat="server"> <ul><%:Html.DisplayForModel()%></ul> </asp:Content> Index2.aspx: To render a Foo. <%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<Foo>" %> <asp:Content ContentPlaceHolderID="MainPlaceHolder" runat="server"> <%:Html.DisplayForModel()%> </asp:Content> Shared\DisplayTemplates\Foo.ascx: A context aware Template for Foo. <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<Foo>" %> <% var tag = typeof(IEnumerable).IsAssignableFrom(ViewData.ModelMetaData.ContainerType) ? "li" : "div"; %> <<%:tag%>><%:Model.Name%></<%:tag%>> The problem with this example is that ViewData.ModelMetaData.ContainerType is null in the Template when resolved though Index1.aspx. From what I've read on Brad Wilson post and others it has to do with the use of IEnumerable and its being an interface. Is there a way to insure that the ContainerType is set? Perhaps by creating a ModelMetadataProviders? I looked into that breifly but it appears the ContainerType value is determined before and then passed to the Provider. Any suggestions would be appreciated.

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  • Hibernate - query caching/second level cache does not work by value object containing subitems

    - by Zoltan Hamori
    Hi! I have been struggling with the following problem: I have a value object containing different panels. Each panel has a list of fields. Mapping: <class name="com.aviseurope.core.application.RACountryPanels" table="CTRY" schema="DBDEV1A" where="PEARL_CTRY='Y'" lazy="join"> <cache usage="read-only"/> <id name="ctryCode"> <column name="CTRY_CD_ID" sql-type="VARCHAR2(2)" not-null="true"/> </id> <bag name="panelPE" table="RA_COUNTRY_MAPPING" fetch="join" where="MANDATORY_FLAG!='N'"> <key column="COUNTRY_LOCATION_ID"/> <many-to-many class="com.aviseurope.core.application.RAFieldVO" column="RA_FIELD_MID" where="PANEL_ID='PE'"/> </bag> </class> I use the following criteria to get the value object: Session m_Session = HibernateUtil.currentSession(); m_Criteria = m_Session.createCriteria(RACountryPanels.class); m_Criteria.add(Expression.eq("ctryCode", p_Country)); m_Criteria.setCacheable(true); As I see the query cache contains only the main select like select * from CTRY where ctry_cd_id=? Both RACountryPanels and RAFieldVO are second level cached. If I check the 2nd level cache content I can see that it cointains the RAFields and the RACountryPanels as well and I can see the select .. from CTRY where ctry_cd_id=... in query cache region as well. When I call the servlet it seems that it is using the cache, but second time not. If I check the content of the cache using JMX, everything seems to be ok, but when I measure the object access time, it seems that it does not always use the cache. Cheers Zoltan

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  • Java List with Objects - find and replace (delete) entry if Object with certain attribute already ex

    - by Sophomore
    Hi there I've been working all day and I somehow can't get this probably easy task figured out - probably a lack of coffee... I have a synchronizedList where some Objects are being stored. Those objects have a field which is something like an ID. These objects carry information about a user and his current state (simplified). The point is, that I only want one object for each user. So when the state of this user changes, I'd like to remove the "old" entry and store a new one in the List. protected static class Objects{ ... long time; Object ID; ... } ... if (Objects.contains(ID)) { Objects.remove(ID); Objects.add(newObject); } else { Objects.add(newObject); } Obviously this is not the way to go but should illustrate what I'm looking for... Maybe the data structure is not the best for this purpose but any help is welcome!

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  • Tiered Design With Analytical Widgets - Is This Code Smell?

    - by Repo Man
    The idea I'm playing with right now is having a multi-leveled "tier" system of analytical objects which perform a certain computation on a common object and then create a new set of analytical objects depending on their outcome. The newly created analytical objects will then get their own turn to run and optionally create more analytical objects, and so on and so on. The point being that the child analytical objects will always execute after the objects that created them, which is relatively important. The whole apparatus will be called by a single thread so I'm not concerned with thread safety at the moment. As long as a certain base condition is met, I don't see this being an unstable design but I'm still a little bit queasy about it. Is this some serious code smell or should I go ahead and implement it this way? Is there a better way? Here is a sample implementation: namespace WidgetTier { public class Widget { private string _name; public string Name { get { return _name; } } private TierManager _tm; private static readonly Random random = new Random(); static Widget() { } public Widget(string name, TierManager tm) { _name = name; _tm = tm; } public void DoMyThing() { if (random.Next(1000) > 1) { _tm.Add(); } } } //NOT thread-safe! public class TierManager { private Dictionary<int, List<Widget>> _tiers; private int _tierCount = 0; private int _currentTier = -1; private int _childCount = 0; public TierManager() { _tiers = new Dictionary<int, List<Widget>>(); } public void Add() { if (_currentTier + 1 >= _tierCount) { _tierCount++; _tiers.Add(_currentTier + 1, new List<Widget>()); } _tiers[_currentTier + 1].Add(new Widget(string.Format("({0})", _childCount), this)); _childCount++; } //Dangerous? public void Sweep() { _currentTier = 0; while (_currentTier < _tierCount) //_tierCount will start at 1 but keep increasing because child objects will keep adding more tiers. { foreach (Widget w in _tiers[_currentTier]) { w.DoMyThing(); } _currentTier++; } } public void PrintAll() { for (int t = 0; t < _tierCount; t++) { Console.Write("Tier #{0}: ", t); foreach (Widget w in _tiers[t]) { Console.Write(w.Name + " "); } Console.WriteLine(); } } } class Program { static void Main(string[] args) { TierManager tm = new TierManager(); for (int c = 0; c < 10; c++) { tm.Add(); //create base widgets; } tm.Sweep(); tm.PrintAll(); Console.ReadLine(); } } }

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  • How to use java.Set

    - by owca
    I'm trying to make it working for quite some time,but just can't seem to get it. I have object Tower built of Block's. I've already made it working using arrays, but I wanted to learn Set's. I'd like to get similar functionality to this: public class Tower { public Tower(){ } public Tower add(Block k1){ //(...) //if block already in tower, return "Block already in tower" } public Tower delete(Block k1){ //(...) //if block already dleted, show "No such block in tower" } } Someone gave me some code, but I constantly get errors when trying to use it : Set<Block> tower = new HashSet<Block>(); boolean added = tower.add( k1 ); if( added ) { System.out.println("Added 1 block."); } else { System.out.println("Tower already contains this block."); } How to implement it ?

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  • Return number of matches from c# dictionary

    - by Rickard Haake
    Hello! I have a dictionary with non unique values and I want to count the matches of a string versus the values. Basically I now do dict.ContainsValue(a) to get a bool telling me if the string a exists in dict, but I want to know not only if it exists but how many times it exists (and maybee even get a list of the keys it exists bound to) Is there a way to do this using dictionary, or should I look for a different collection? /Rickard Haake

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  • .NET SortedDictionary But Sorted By Values

    - by Michael Covelli
    I need a data structure that acts like a SortedDictionary<int, double> but is sorted based on the values rather than the keys. I need it to take about 1-2 microseconds to add and remove items when we have about 3000 items in the dictionary. My first thought was simply to switch the keys and values in my code. This very nearly works. I can add and remove elements in about 1.2 microseconds in my testing by doing this. But the keys have to be unique in a SortedDictionary so that means that values in my inverse dictionary would have to be unique. And there are some cases where they may not be. Any ideas of something in the .NET libraries already that would work for me?

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  • How to implement List, Set, and Map in null free design?

    - by Pyrolistical
    Its great when you can return a null/empty object in most cases to avoid nulls, but what about Collection like objects? In Java, Map returns null if key in get(key) is not found in the map. The best way I can think of to avoid nulls in this situation is to return an Entry<T> object, which is either the EmptyEntry<T>, or contains the value T. Sure we avoid the null, but now you can have a class cast exception if you don't check if its an EmptyEntry<T>. Is there a better way to avoid nulls in Map's get(K)? And for argument sake, let's say this language don't even have null, so don't say just use nulls.

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  • Why collection literals ?

    - by Green Hyena
    Hi fellow Java programmers. From the various online articles on Java 7 I have come to know that Java 7 will be having collection literals like the following: List<String> fruits = [ "Apple", "Mango", "Guava" ]; Set<String> flowers = { "Rose", "Daisy", "Chrysanthemum" }; Map<Integer, String> hindiNums = { 1 : "Ek", 2 : "Do", 3 : "Teen" }; My questions are: 1] Wouldn't it have been possible to provide a static method of in all of the collection classes which could be used as follows: List<String> fruits = ArrayList.of("Apple", "Mango", "Guava"); IMO this looks as good as the literal version and is also reasonably concise. Why then did they have to invent a new syntax? 2] When I say List<String> fruits = [ "Apple", "Mango", "Guava" ]; what List would I actually get? Would it be ArrayList or LinkedList or something else? Thanks.

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  • Confused over behavior of List.mapi in F#

    - by James Black
    I am building some equations in F#, and when working on my polynomial class I found some odd behavior using List.mapi Basically, each polynomial has an array, so 3*x^2 + 5*x + 6 would be [|6, 5, 3|] in the array, so, when adding polynomials, if one array is longer than the other, then I just need to append the extra elements to the result, and that is where I ran into a problem. Later I want to generalize it to not always use a float, but that will be after I get more working. So, the problem is that I expected List.mapi to return a List not individual elements, but, in order to put the lists together I had to put [] around my use of mapi, and I am curious why that is the case. This is more complicated than I expected, I thought I should be able to just tell it to make a new List starting at a certain index, but I can't find any function for that. type Polynomial() = let mutable coefficients:float [] = Array.empty member self.Coefficients with get() = coefficients static member (+) (v1:Polynomial, v2:Polynomial) = let ret = List.map2(fun c p -> c + p) (List.ofArray v1.Coefficients) (List.ofArray v2.Coefficients) let a = List.mapi(fun i x -> x) match v1.Coefficients.Length - v2.Coefficients.Length with | x when x < 0 -> ret :: [((List.ofArray v1.Coefficients) |> a)] | x when x > 0 -> ret :: [((List.ofArray v2.Coefficients) |> a)] | _ -> [ret]

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  • Performance for myCollection.Add() vs. myCollection["key"]

    - by Atomiton
    When dealing with a collection of key/value pairs is there any difference between using its Add() method and directly assigning it? For example, a HtmlGenericControl will have an Attributes Collection: var anchor = new HtmlGenericControl("a"); // These both work: anchor.Attributes.Add("class", "xyz"); anchor.Attributes["class"] = "xyz"; Is it purely a matter of preference, or is there a reason for doing one or the other?

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  • Bind ISet in ASP.NET MVC2

    - by Dmitriy Nagirnyak
    Hi, I am trying to find out what would be the best bind first element of ISet (Iesi.Collection) as a first element. So basically I only have to use some kind of collection that has an indexer (and ISet doesn't) then I can write code like this (which works perfectly well): <%: Html.EditorFor(x => x.Company.PrimaryUsers[0].Email) %> But as the ISet has no indexer I cannot use it. So how can I then bind the first element of ISet in MVC2? Thanks, Dmitriy.

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  • Excel VBA: Passing a collection from a class to a module issue

    - by Martin
    Hello, I have been trying to return a collection from a property within a class to a routine in a normal module. The issue I am experiencing is that the collection is getting populated correctly within the property in the class (FetchAll) but when I pass the collection back to the module (Test) all the entries are populated with the last item in the list. This is the Test sub-routine in the standard module: Sub Test() Dim QueryType As New QueryType Dim Item Dim QueryTypes As Collection Set QueryTypes = QueryType.FetchAll For Each Item In QueryTypes Debug.Print Item.QueryTypeID, _ Left(Item.Description, 4) Next Item End Sub This is the FetchAll property in the QueryType class: Public Property Get FetchAll() As Collection Dim RS As Variant Dim Row As Long Dim QTypeList As Collection Set QTypeList = New Collection RS = .Run ' populates RS with a record set from a database (as an array), ' some code removed ' goes through the array and sets up objects for each entry For Row = LBound(RS, 2) To UBound(RS, 2) Dim QType As New QueryType With QType .QueryTypeID = RS(0, Row) .Description = RS(1, Row) .Priority = RS(2, Row) .QueryGroupID = RS(3, Row) .ActiveIND = RS(4, Row) End With ' adds new QType to collection QTypeList.Add Item:=QType, Key:=CStr(RS(0, Row)) Debug.Print QTypeList.Item(QTypeList.Count).QueryTypeID, _ Left(QTypeList.Item(QTypeList.Count).Description, 4) Next Row Set FetchAll = QTypeList End Property This is the output I get from the debug in FetchAll: 1 Numb 2 PBM 3 BPM 4 Bran 5 Claw 6 FA C 7 HNW 8 HNW 9 IFA 10 Manu 11 New 12 Non 13 Numb 14 Repo 15 Sell 16 Sms 17 SMS 18 SWPM This is the output I get from the debug in Test: 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM 18 SWPM Anyone got any ideas? I am probably totally overlooking something! Thanks, Martin

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  • java.lang.ClassNotFoundException using google commons

    - by pie154
    I have two classes inside a package. Both call a method from another class, one works perfectly fine and the other gives the error java.lang.ClassNotFoundException and the error java.lang.NoClassDefFoundError: com/google/common/base/Predicate The class path should be the same for both as they are in he same package so I can't figure out why one has access to the class and the other doesn't? thanks in advance for any help given.

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