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  • How to initialize list with parent child relation

    - by user2917702
    Let's say I have the following classes. public class Parent { public string name; IList<Children> children; } public class Child { public string parentName; public int age; } As it is understandable, each parent can have multiple children, and we can have multiple parents. What is the best way to initialize these classes? Is it better to get all of the parents, and all of the children from database then use LINQ? IList<Parent> parents = GetParents()//assume this gets parents from db IList<Child> children = GetChildren() //assume this gets children from db foreach(Parent parent in parents) { parent.children = children.Where(x=>x.parentName==parent.name).ToList(); } or get all of the parents and iterate through each parent to query database by parentName to get children information? Due to requirement that I have, I cannot use datatable or dataset; I can only use datareader. IList<Parent> parents = GetParents()//assume this gets parents from db foreach(Parent parent in parents) { parent.children = GetChildrenByParentName();//assume this gets parents from db by parentName } Thank you

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  • Sorting an ArrayList of Contacts

    - by Sameera0
    Ok so I have a been making an addressbook application and have pretty much finished all the key features but I am looking to implement a sort feature in the program. I want to sort an Arraylist which is of a type called Contact (contactArray) which is a separate class which contains four fields; name, home number, mobile number and address. So I was looking into using the collection sort yet am not sure how i'd implement this. Is this the right sort I should be using / is it possible to use or should I look into making a custom sort?

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  • WPF How to bind to a specific element in the Collection

    - by PaN1C_Showt1Me
    Hi, I want to make a binding to a specific element in the Collection. But I cannot figure out how to write the Binding. This is the code: public class MySource { .. public string SomeProp; public ICollection<T> MyCollection; .. } this.DataContext = new MySource(); <TextBox Text={Binding SomeProp} /> <TextBox Text={Binding FIRST_ELEMENT_OF_THE_MyCollection} /> <TextBox Text={Binding SECOND_ELEMENT_OF_THE_MyCollection} /> <!--Ignore other elements--> Try to replace those binding strings, please Thank you

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  • Use LINQ, to Sort and Filter items in a List<ReturnItem> collection, based on the values within a Li

    - by Daniel McPherson
    This is tricky to explain. We have a DataTable that contains a user configurable selection of columns, which are not known at compile time. Every column in the DataTable is of type String. We need to convert this DataTable into a strongly typed Collection of "ReturnItem" objects so that we can then sort and filter using LINQ for use in our application. We have made some progress as follows: We started with the basic DataTable. We then process the DataTable, creating a new "ReturnItem" object for each row This "ReturnItem" object has just two properties: ID ( string ) and Columns( List(object) ). The properties collection contains one entry for each column, representing a single DataRow. Each property is made Strongly Typed (int, string, datetime, etc). For example it would add a new "DateTime" object to the "ReturnItem" Columns List containing the value of the "Created" Datatable Column. The result is a List(ReturnItem) that we would then like to be able to Sort and Filter using LINQ based on the value in one of the properties, for example, sort on "Created" date. We have been using the LINQ Dynamic Query Library, which gets us so far, but it doesn't look like the way forward because we are using it over a List Collection of objects. Basically, my question boils down to: How can I use LINQ, to Sort and Filter items in a List(ReturnItem) collection, based on the values within a List(object) property which is part of the ReturnItem class?

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  • Difference between a Deprecated and Legacy API?

    - by Vaibhav Bajpai
    I was studying the legacy API's in the Java's Collection Framework and I learnt that classes such as Vector and HashTable have been superseded by ArrayList and HashMap. However still they are NOT deprecated, and deemed as legacy when essentially, deprecation is applied to software features that are superseded and should be avoided, so, I am not sure when is a API deemed legacy and when it is deprecated.

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  • Retrieve KEYWORDS from META tag in a HTML WebPage using JAVA.

    - by kooldave98
    Hello all, I want to retrieve all the content words from a HTML WebPage and all the keywords contained in the META TAG of the same HTML webpage using Java. For example, consider this html source code: <html> <head> <meta name = "keywords" content = "deception, intricacy, treachery"> </head> <body> My very short html document. <br> It has just 2 'lines'. </body> </html> The CONTENT WORDS here are: my, very, short, html, document, it, has, just, lines Note: The punctuation and the number '2' are ruled out. The KEYWORDS here are: deception, intricacy, treachery I have created a class for this purpose called WebDoc, this is as far as I have been able to get. import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.net.URL; import java.util.Set; import java.util.TreeSet; public class WebDoc { protected URL _url; protected Set<String> _contentWords; protected Set<String> _keyWords public WebDoc(URL paramURL) { _url = paramURL; } public Set<String> getContents() throws IOException { //URL url = new URL(url); Set<String> contentWords = new TreeSet<String>(); BufferedReader in = new BufferedReader(new InputStreamReader(_url.openStream())); String inputLine; while ((inputLine = in.readLine()) != null) { // Process each line. contentWords.add(RemoveTag(inputLine)); //System.out.println(RemoveTag(inputLine)); } in.close(); System.out.println(contentWords); _contentWords = contentWords; return contentWords; } public String RemoveTag(String html) { html = html.replaceAll("\\<.*?>",""); html = html.replaceAll("&",""); return html; } public Set<String> getKeywords() { //NO IDEA ! return null; } public URL getURL() { return _url; } @Override public String toString() { return null; } }

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  • Disable Adding Item to Collection

    - by Wonko the Sane
    Hi All, I'm sure there's an "easy" answer to this, but for the moment it escapes me. In an MVVM application, I have a property that is a ObservableCollection, used for displaying some set of elements on the view. private readonly ObservableCollection<MyType> mMyCollection = new ObservableCollection<MyType>(); public ObservableCollection<MyType> MyCollection { get { return mMyCollection; } } I want to restrict consumers of this collection from simply using the property to add to the collection (i.e. I want to prevent this from the view): viewModel.MyCollection.Add(newThing); // want to prevent this! Instead, I want to force the use of a method to add items, because there may be another thread using that collection, and I don't want to modify the collection while that thread is processing it. public void AddToMyCollection(MyType newItem) { // Do some thread/task stuff here } Thanks, wTs

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  • Why does Ordered[A] use a compare method instead of reusing compareTo?

    - by soc
    trait Ordered[A] extends java.lang.Comparable[A] { def compare(that: A): Int def < (that: A): Boolean = (this compare that) < 0 def > (that: A): Boolean = (this compare that) > 0 def <= (that: A): Boolean = (this compare that) <= 0 def >= (that: A): Boolean = (this compare that) >= 0 def compareTo(that: A): Int = compare(that) } Isn't it a bit useless to have both compare and compareTo? What is the huge benefit I'm missing here? If they had just used compareTo I could just had replaced Comparable with Ordered in my code and be done.

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  • capture types of varargs parameters

    - by IttayD
    Hi, I'd like to define a method accepting varargs, so that I get the types with which it was called even in the case of nulls. def foo(args: Any*) = .... val s: String = null foo(1, s) // i'd like to be able to tell in foo that args(0) is Int, args(1) is String

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  • How can I make three partials into just one in rails where the :collection is the same?

    - by Angela
    I have three partials that I'd like to consolidate into one. They share the same collection, but each gets passed its own :local variable. Those variables are used for specific Models, so as a result, I have three different calls to the partial and three different partials. Here's the repetitive code: <% for email in campaign.emails %> <h4><%= link_to email.title, email %> <%= email.days %> days</h4> <% @contacts= campaign.contacts.find(:all, :order => "date_entered ASC" )%> <!--contacts collection--> <!-- render the information for each contact --> <%= render :partial => "contact_email", :collection => @contacts, :locals => {:email => email} %> <% end %> Calls in this Campaign: <% for call in campaign.calls %> <h4><%= link_to call.title, call %> <%= call.days %> days</h4> <% @contacts= campaign.contacts.find(:all, :order => "date_entered ASC" )%> <!--contacts collection--> <!-- render the information for each contact --> <%= render :partial => "contact_call", :collection => @contacts, :locals => {:call => call} %> <% end %> Letters in this Campaign: <% for letter in campaign.letters %> <h4><%= link_to letter.title, letter %> <%= letter.days %> days</h4> <% @contacts= campaign.contacts.find(:all, :order => "date_entered ASC" )%> <!--contacts collection--> <!-- render the information for each contact --> <%= render :partial => "contact_letter", :collection => @contacts, :locals => {:letter => letter} %> <% end %> An example of one of the partials is as follows: < div id="contact_email_partial"> <% if from_today(contact_email, email.days) < 0 %> <% if show_status(contact_email, email) == 'no status'%> <p> <%= full_name(contact_email) %> <% unless contact_email.statuses.empty?%> (<%= contact_email.statuses.find(:last).status%>) <% end %> is <%= from_today(contact_email,email.days).abs%> days overdue: <%= do_event(contact_email, email) %> <%= link_to_remote "Skip Email Remote", :url => skip_contact_email_url(contact_email,email), :update => "update-area-#{contact_email.id}-#{email.id}" %> <span id='update-area-<%="#{contact_email.id}-#{email.id}"%>'> </span> <% end %> <% end %> </div>

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  • How to bind WPF TreeView to a List<Drink> programmatically?

    - by Joan Venge
    So I am very new to WPF and trying to bind or assign a list of Drink values to a wpf treeview, but don't know how to do that, and find it really hard to find anything online that just shows stuff without using xaml. struct Drink { public string Name { get; private set; } public int Popularity { get; private set; } public Drink ( string name, int popularity ) : this ( ) { this.Name = name; this.Popularity = popularity; } } List<Drink> coldDrinks = new List<Drink> ( ){ new Drink ( "Water", 1 ), new Drink ( "Fanta", 2 ), new Drink ( "Sprite", 3 ), new Drink ( "Coke", 4 ), new Drink ( "Milk", 5 ) }; } } How can I do this in code? For example: treeview1.DataItems = coldDrinks; and everything shows up in the treeview.

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  • Java LinkedList iterator being exhausted prematurely

    - by Sujeet
    I am using LinkedList and retrieving an Iterator object by using list.iterator(). After that, I am checking it.hasNext(), real issue is while checking it.hasNext(), sometimes it returns false. I need help why this is happening, though I have elements in the list. Some code: public synchronized void check(Object obj) throws Exception { Iterator itr = list.iterator(); while(itr.hasNext()) { //This Line I get false.. though i have list size is 1 Item p = (Item)itr.next(); if(p.getId() == null) {continue;} if(p.getId().getElemntId() == obj.getId() || obj.getId() == 0 ) { p.setResponse(obj); notifyAll(); return; } } Log.Error("validate failed obj.getId="+obj.getId()+" **list.size="+list.size()*This shows 1*); throw new Exception("InvalidData"); }

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  • Merge object from list by comparing one value

    - by Bala
    I have two List of Objects (one is master list and other is error list) and if there is a match of one value when compared two lists then merge all other error list values into mast list value (only one object). Other than iterating is there any other way to compare a value and then merge that object. Object is a Value object with some setters and getters. Appreciate your help. List<OrderVO> masterList; List<OrderVO> errorList; If errorList.OrderVO.getOrderID = masterList.OrderVO.getOrderID then masterList.OrderVO.merge(errorList.OrderVO) or copy all values of masterList.OrderVO.copy(errorList.OrderVO). Hoper this is clear

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  • Compiler error when using abstract types

    - by Dylan
    I'm trying to implement a "protocol helper" trait that is responsible for matching up Prompts and Responses. The eventual goal is to have an object that defines the various Prompt and Response classes as subclasses of a sealed trait, then have a class that mixes in the ProtocolSupport trait for that Protocol object. The problem is that my current approach won't compile, even though I'm fairly sure it should. Here's a distilled version of what I've got: trait Protocol { type Response type Prompt <: BasePrompt trait BasePrompt { type Data def validate(response: Response): Validated[Data] } } trait ProtocolSupport[P <: Protocol] { def foo(prompt: P#Prompt, response: P#Response) = { // compiler error prompt.validate(response) } } The compiler doesn't like the response as an argument to prompt.validate: [error] found : response.type (with underlying type P#Response) [error] required: _4.Response where val _4: P [error] prompt.validate(response) [error] ^ This isn't very helpful.. it seems to say that it wants a P.Response but that's exactly what I'm giving it, so what's the problem?

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  • Is it okay to violate the principle that collection properties should be readonly for performance?

    - by uriDium
    I used FxCop to analyze some code I had written. I had exposed a collection via a setter. I understand why this is not good. Changing the backing store when I don't expect it is a very bad idea. Here is my problem though. I retrieve a list of business objects from a Data Access Object. I then need to add that collection to another business class and I was doing it with the setter method. The reason I did this was that it is going to be faster to make an assignment than to insert hundreds of thousands of objects one at a time to the collection again via another addElement method. Is it okay to have a getter for a collection in some scenarios? I though of rather having a constructor which takes a collection? I thought maybe I could pass the object in to the Dao and let the Dao populate it directly? Are there any other better ideas?

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  • What's the difference between => , ()=>, and Unit=>

    - by Malvolio
    I'm trying to represent a function that takes no arguments and returns no value (I'm simulating the setTimeout function in JavaScript, if you must know.) case class Scheduled(time : Int, callback : => Unit) doesn't compile, saying " `val' parameters may not be call-by-name" case class Scheduled(time : Int, callback : () => Unit) compiles, but has to be invoked strangely, instead of Scheduled(40, { println("x") } ) I have to do this Scheduled(40, { () => println("x") } ) What also works is class Scheduled(time : Int, callback : Unit => Unit) but is invoked in an even-less-sensible way Scheduled(40, { x : Unit => println("x") } ) (What would a variable of type Unit be?) What I want of course is a constructor that can be invoke the way I would invoke it if it were an ordinary function: Scheduled(40, println("x") ) Give baby his bottle!

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  • Dividing a list in specific number of sublists

    - by Surya
    I want to divide a list in "a specific number of" sublists. That is, for example if I have a list List(34, 11, 23, 1, 9, 83, 5) and the number of sublists expected is 3 then I want List(List(34, 11), List(23, 1), List(9, 83, 5)). How do I go about doing this? I tried grouped but it doesn't seem to be doing what I want. PS: This is not a homework question. Kindly give a direct solution instead of some vague suggestions.

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  • Difference between a Deprecated and an Legacy API?

    - by Vaibhav Bajpai
    I was studying the legacy API's in the Java's Collection Framework and I learnt that classes such as Vector and HashTable have been superseded by ArrayList and HashMap. However still they are NOT deprecated, and deemed as legacy when essentially, deprecation is applied to software features that are superseded and should be avoided, so, I am not sure when is a API deemed legacy and when it is deprecated.

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  • Can I have a set containing identical elements?

    - by Roman
    It is convenient for me to use a set. I like how I can "add" ("remove") an element to (from) the set. It is also convenient to check if a given element is in the set. The only problem, I found out that I cannot add a new element to a set if the set has already such an element. Is it possible to have "sets" which can contain several identical elements.

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