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  • How do I create a class repository in Java and do I really need it?

    - by Roman
    I have a large number of objects which are identified by names (strings). So, I would like to have a kind of mapping from object name to the class instances. I was told that in this situation I can use a "repository" class which works like that: Server myServer = ServerRepository.getServer("NameOfServer"); So, if there is already an object (sever) with the "NameOfServer" it will be returned by the "getServer". If such an object does not exist yet, it will be created and returned by the "getServer". So, my question is how to program such a "repository" class? In this class I have to be able to check if there is an instance of a given class such that it has a given value of a given field. How can I do it? I need to have a kind of loop over all existing object of a given class? Another part of my question is why I cannot use associative arrays (associative container, map, mapping, dictionary, finite map)? (I am not sure how do you call it in Java) In more details, I have an "array" which maps names of objects to objects. So, whenever I create a new object, I add a new element to the array: myArray["NameOfServer"] = new Server("NameOfServer").

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  • Is there a way to add extra fields to an association in the ADO.NET Entity Framework?

    - by bigbird1040
    I would like to be able to model a many-to-many relationship that has extra details about the relationship. For example: Person: int id, String name Project: int id, String name ProjectPerson: Person.id, Project.id, String role Whenever I create the ProjectPerson association in the EF, I am unable to add the role attribute to the association. If I create the tables in my DB and then import it into the model, I lose the extra properties.

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  • What is the meaning of ": base" in the costructor definition ?

    - by DotNetBeginner
    What is the meaning of ": base" in the costructor of following class(MyClass) ? Please explain the concept behind constructor definition given below for class MyClass. public class MyClass: WorkerThread { public MyClass(object data): base(data) { // some code } } public abstract class WorkerThread { private object ThreadData; private Thread thisThread; public WorkerThread(object data) { this.ThreadData = data; } public WorkerThread() { ThreadData = null; } }

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  • asp.net session error

    - by umeshchaurasia
    HI all, I am working with asp.net with c#.net Here i am using session state to pass the value from one page to another. i have two pages, in first page i am calculating the value and passing the value to second page using session and in second page i am displaying the message through the value. I am using these two pages for facebook application. I uploaded my two pages then i am checking with facebook by opening through internet explorer and its giving below error. Object reference not set to an instance of an object. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.NullReferenceException: Object reference not set to an instance of an object. But when i open my application using firefox the pages are working fine. please help me...

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  • Unresponsive UI when using BeginInvoke

    - by Kazoom
    Bckground I have a networked application written in C#. my server program has a UI and several communication threads, that read from tcp sockets and display messages on controller UI. Communication with each client is done through a seprate thread. When i recieve some stream of messages from one client , the thread for that client writes on UI, which is a richtextbox on a Form. I call SetTextHelper(string text) method of the form. which looks like this private delegate void MyTextUpdateHandler(string text); public void SetTextHelper(string text) { BeginInvoke(new MyTextUpdateHandler(SetText), new object[] { text }); } public setText(string text) { richtext.Text= text; } Question - If i use BeginInvoke my UI is entirely unresponsive when i m writing large stream of data to UI - Invoke solves that problem, but i read that for multi threaded environment where many thereads are sharing same resource Invoke can lead to deadlocks I share the common ichtextbox between around 16 threads - What would be a good desing for my situation?

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  • How to combine ASCII text files, then encrypt, then decrypt, and put into a 'File' Class? C++

    - by Joel
    For example, if I have three ASCII files: file1.txt file2.txt file3.txt ...and I wanted to combine them into one encrypted file: database.txt Then in the application I would decrypt the database.txt and put each of the original files into a 'File' class on the heap: class File{ public: string getContents(); void setContents(string data); private: string m_data; }; Is there some way to do this? Thanks

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  • Passing variable from main to Async class

    - by Bigflow
    Somehow, I can't get this done. This is all what I tried till now: Main: private String myState; public String getState() { return myState; } public void setState(String s) { myState = s; } Async: Main appState = ((Main)getApplicationContext()); String state = appState.getState(); Error: No enclosing instance of the type Main is accessible in scope Tried with Helper(Globals) class. public class Globals extends Application{ private String test= "1"; } Main: private Globals mGlobals; mGlobals = new Globals(); mGlobals.test = "2"; //Do Async thing Async: private Globals mGlobals; mGlobals = new Globals(); print mGlobals.test; // (result is 1, should be 2) Also something else, but don't remember good. Tried alot of things (backspace and del buttons are over-used :p ) But I can't get everything working. Async class doesn't have an activity. Code pasted: http://pastebin.com/ikcsdL1p

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  • HQL multiple updates. Is there a better way?

    - by folone
    I have a Map, that I want to persist. The domain object is something like this: public class Settings { private String key; private String value; public String getKey() { ... } public String getValue() { ... } public void setKey() { ... } public void setValue() { ... } } The standard approach is to generate a Setting for each pair, and saveOrUpdate() it. But it generates way too much queries, because I need to save lots of settings at a time, and it really affects perfomance. Is there a way to do this using one update query?

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  • Simple RSA encryption (Java)

    - by jake blue
    This is simply for fun. This will not be used for any actual encryption. I'm only first year comp sci student and love cryptography. This took a long time to get working. At approximately N = 18, it begins breaking down. It won't encrypt messages properly after that point. I'm not sure why. Any insights? I'd also appreciate any links you could provide me to tutorials or interesting reading about Cryptography. import java.math.BigInteger; import java.security.SecureRandom; /** * Cryptography. * * Generates public and private keys used in encryption and * decryption * */ public class RSA { private final static BigInteger one = new BigInteger("1"); private final static SecureRandom random = new SecureRandom(); // prime numbers private BigInteger p; private BigInteger q; // modulus private BigInteger n; // totient private BigInteger t; // public key private BigInteger e; // private key private BigInteger d; private String cipherText; /** * Constructor for objects of class RSA */ public RSA(int N) { p = BigInteger.probablePrime(N/2, random); q = BigInteger.probablePrime(N/2, random); // initialising modulus n = p.multiply(q); // initialising t by euclid's totient function (p-1)(q-1) t = (p.subtract(one)).multiply(q.subtract(one)); // initialising public key ~ 65537 is common public key e = new BigInteger("65537"); } public int generatePrivateKey() { d = e.modInverse(t); return d.intValue(); } public String encrypt(String plainText) { String encrypted = ""; int j = 0; for(int i = 0; i < plainText.length(); i++){ char m = plainText.charAt(i); BigInteger bi1 = BigInteger.valueOf(m); BigInteger bi2 = bi1.modPow(e, n); j = bi2.intValue(); m = (char) j; encrypted += m; } cipherText = encrypted; return encrypted; } public String decrypt() { String decrypted = ""; int j = 0; for(int i = 0; i < cipherText.length(); i++){ char c = cipherText.charAt(i); BigInteger bi1 = BigInteger.valueOf(c); BigInteger bi2 = bi1.modPow(d, n); j = bi2.intValue(); c = (char) j; decrypted += c; } return decrypted; } }

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  • due at midnight - program compiles but has logic error(s)

    - by Leslie Laraia
    not sure why this program isn't working. it compiles, but doesn't provide the expected output. the input file is basically just this: Smith 80000 Jones 100000 Scott 75000 Washington 110000 Duffy 125000 Jacobs 67000 Here is the program: import java.io.File; import java.io.FileNotFoundException; import java.util.Scanner; /** * * @author Leslie */ public class Election { /** * @param args the command line arguments */ public static void main(String[] args) throws FileNotFoundException { // TODO code application logic here File inputFile = new File("C:\\Users\\Leslie\\Desktop\\votes.txt"); Scanner in = new Scanner(inputFile); int x = 0; String line = ""; Scanner lineScanner = new Scanner(line); line = in.nextLine(); while (in.hasNextLine()) { line = in.nextLine(); x++; } String[] senatorName = new String[x]; int[] votenumber = new int[x]; double[] votepercent = new double[x]; System.out.printf("%44s", "Election Results for State Senator"); System.out.println(); System.out.printf("%-22s", "Candidate"); //Prints the column headings to the screen System.out.printf("%22s", "Votes Received"); System.out.printf("%22s", "%of Total Votes"); int i; for(i=0; i<x; i++) { while(in.hasNextLine()) { line = in.nextLine(); String candidateName = lineScanner.next(); String candidate = candidateName.trim(); senatorName[i] = candidate; int votevalue = lineScanner.nextInt(); votenumber[i] = votevalue; } } votepercent = percentages(votenumber, x); for (i = 0; i < x; i++) { System.out.println(); System.out.printf("%-22s", senatorName[i]); System.out.printf("%22d", votenumber[i]); System.out.printf("%22.2f", votepercent[i]); System.out.println(); } } public static double [] percentages(int[] votenumber, int z) { double [] percentage = new double [z]; double total = 0; for (double element : votenumber) { total = total + element; } for(int i=0; i < votenumber.length; i++) { int y = votenumber[i]; percentage[i] = (y/total) * 100; } return percentage; } }

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  • Django query filter a set of data

    - by dana
    if a have a query like following = Relations.objects.filter(initiated_by = request.user) in which i'm having all the users followed by the currently logged in user, and i want to display those user's blog posts. Using a query like: blog = New.objects.filter(created_by = following) it only shows me the blog posts of the user with the id = 1 (though the currently logged in user doesn't actually follow him) in template i have : {% for object in blog %} <a href='/accounts/profile_view/{{object.created_by}}/'> {{object.created_by}}</a> <br /> {{object.post}}<br /> {% endfor %} Where am i wrong?

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  • dynamically embedding youtube videos with jquery

    - by danwoods
    Hello all, I'm trying to retrieve a listing of a user's youtube videos and embed them in a page using jQuery. My code looks something like this: $(document).ready(function() { //some variables var fl_obj_template = $('<object width="260" height="140">' + '<param name="movie" value=""></param>' + '<param name="allowFullScreen" value="true"></param>' + '<param name="allowscriptaccess" value="always"></param>' + '<embed src="" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="260" height="140"></embed>' + '</object>'); var video_elm_arr = $('.video'); //hide videos until ready $('.video').addClass('hidden'); //pull video data from youtube $.ajax({ url: 'http://gdata.youtube.com/feeds/api/users/username/uploads?alt=json', dataType: 'jsonp', success: function(data) { $.each(data.feed.entry, function(i,item){ //only take the first 7 videos if(i > 6) return; //give the video element a flash object var cur_flash_obj = fl_obj_template; //assign title $(video_elm_arr[i]).find('.video_title').html(item.title.$t); //clean url var video_url = item.media$group.media$content[0].url; var index = video_url.indexOf("?"); if (index > 0) video_url = video_url.substring(0, index); //and asign it to the player's parameters $(cur_flash_obj).find('object param[name="movie"]').attr('value', video_url); $(cur_flash_obj).find('object embed').attr('src', video_url); //alert(cur_flash_obj); //insert flash object in video element $(video_elm_arr[i]).append(cur_flash_obj); //and show $(video_elm_arr[i]).removeClass('hidden'); }); } }); }); (of course with 'username' being the actual username). The video titles appear correctly but no videos show up. What gives? The target html looks like: <div id="top_row_center" class="video_center video"> <p class="video_title"></p> </div>

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  • What is the best way to handle the Connections to MySql from c#

    - by srk
    I am working on a c# application which connects to MySql server. There are about 20 functions which will connect to database. This application will be deployed in 200 over machines. I am using the below code to connect to my database which is identical for all the functions. The problem is, i can some connections were not closed and still alive when deployed in 200 over machines. Connection String : <add key="Con_Admin" value="server=test-dbserver; database=test_admindb; uid=admin; password=1Password; Use Procedure Bodies=false;" /> Declaration of the connection string Globally in application [Global.cs] : public static MySqlConnection myConn_Instructor = new MySqlConnection(ConfigurationSettings.AppSettings["Con_Admin"]); Function to query database : public static DataSet CheckLogin_Instructor(string UserName, string Password) { DataSet dsValue = new DataSet(); //MySqlConnection myConn = new MySqlConnection(ConfigurationSettings.AppSettings["Con_Admin"]); try { string Query = "SELECT accounts.str_nric AS Nric, accounts.str_password AS `Password`," + " FROM accounts " + " WHERE accounts.str_nric = '" + UserName + "' AND accounts.str_password = '" + Password + "\'"; MySqlCommand cmd = new MySqlCommand(Query, Global.myConn_Instructor); MySqlDataAdapter da = new MySqlDataAdapter(); if (Global.myConn_Instructor.State == ConnectionState.Closed) { Global.myConn_Instructor.Open(); } cmd.ExecuteScalar(); da.SelectCommand = cmd; da.Fill(dsValue); Global.myConn_Instructor.Close(); } catch (Exception ex) { Global.myConn_Instructor.Close(); ExceptionHandler.writeToLogFile(System.Environment.NewLine + "Target : " + ex.TargetSite.ToString() + System.Environment.NewLine + "Message : " + ex.Message.ToString() + System.Environment.NewLine + "Stack : " + ex.StackTrace.ToString()); } return dsValue; }

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  • C# sqlite syntax in ASP.NET?

    - by acidzombie24
    -edit- This is no longer relevant and the question doesnt make sense to me anymore. I think i wanted to know how to create tables or know if the syntax is the same from winform to ASP.NET I am very use to sqlite http://sqlite.phxsoftware.com/ and would like to create a DB in a similar style. How do i do this? it doesnt need to be the same, just similar enough for me to enjoy. An example of the syntax. connection = new SQLiteConnection("Data Source=" + sz +";Version=3"); command = new SQLiteCommand(connection); connection.Open(); command.CommandText = "CREATE TABLE if not exists miscInfo(key TEXT, " + "value TEXT, UNIQUE (key));"; command.ExecuteNonQuery(); The @name is a symbol and command.Parameters.Add("@userDesc", DbType.String).Value = d.userDesc; replaces the symbol with escaped values/texts/blob command.CommandText = "INSERT INTO discData(rootfolderID, time, volumeName, discLabel, " + "userTitle, userDesc) "+ "VALUES(@rootfolderID, @time, @volumeName, @discLabel, " + "@userTitle, @userDesc); " + "SELECT last_insert_rowid() AS RecordID;"; command.Parameters.Add("@rootfolderID", DbType.Int64).Value = d.rootfolderID; command.Parameters.Add("@time", DbType.Int64).Value = d.time; command.Parameters.Add("@volumeName", DbType.String).Value = d.volumeName; command.Parameters.Add("@discLabel", DbType.String).Value = d.discLabel; command.Parameters.Add("@userTitle", DbType.String).Value = d.userTitle; command.Parameters.Add("@userDesc", DbType.String).Value = d.userDesc; d.discID = (long)command.ExecuteScalar();

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  • Console class in java Exception in reading password

    - by satheesh
    Hi, i am trying to use Console class in java. with this code import java.io.Console; public class ConsoleClass { public static void main(String[] args){ Console c=System.console(); char[] pw; pw=c.readPassword("%s","pw :"); for(char ch:pw){ c.format("%c",ch); } c.format("\n"); MyUtility mu =new MyUtility(); while(true){ String name=c.readLine("%s", "input?: "); c.format("output: %s \n",mu.doStuff(name)); } } } class MyUtility{ String doStuff(String arg1){ return "result is " +arg1; } } here i am getting NullPointerException when i tried to run in netbeans but i am not getting any Exception when tried to run in cmd with out netbeans IDE.Why?

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  • Using 'or' in Java Generics declaration

    - by Shervin
    I have a method that returns an instance of Map<String, List<Foo>> x(); and another method that returns an instance of Map<String, Collection<Foo>> y(); Now if I want to dynamically add one of this Maps in my field, how can I write the generics for it to work? ie: public class Bar { private Map<String, ? extends Collection<Foo>> myMap; public void initializer() { if(notImportant) myMap = x(); //OK else myMap = y(); // !OK (Need cast to (Map<String, ? extends Collection<Foo>>) } Now is it ok that I cast to the signature even though the y() is declared as being Collection? } } If it is not ok to cast, can I somehow write this (Collection OR List) I mean, List is a Collection, so it should somehow be possible. private Map<String, Collection<Foo> | List<Foo>>> myMap;

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  • An inaccessible class. VS2010.

    - by Mishgun_
    I realy dont know what the problem is with VS2010. I created a class, and when I'm trying create an exemplar of the class I get an error: "Error xxx is inaccessible due to its protection level. Example: public class Person { Person(string name, int age) { this.name = name; this.age = age; } public string name; public int age; } class Program { static void Main(string[] args) { Person ps = new Person("Jack", 19); } }

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  • Problems breaking out of nested loops

    - by user1040281
    I have problems breaking out off these nested loops correctly. What the code is trying to do is to indicate that a customer has rented a certain movie. Both the movie and customer are compared to properties of arraylist objects and then if all checks out the name property and ID property of a movie object are added as a string to another arraylist. All this works correctly as long as I use the first movie (from movies) and the first customer (from customers) but if I try renting other movies further down my arraylist with other customers then it adds the rented movie to the customerRentedMovies arraylist but prints out the "else message". I figure I need to break out of the foreach(blabla) loops aswell? or could goto be used? Comments was removed (looked kinda messy, can explain further if needed) public void RentMovie(string titel, int movieID, string name, int customerID) { foreach (Customer customer in customers) { if (name == customer.Name && customerID == customer.CustomerID) { foreach (MovieInfo movie in movies) { if (titel == movie.Titel && movieID == movie.MovieID) { movie.rented = true; string rentedMovie = string.Format("{0} ID: {1}", movie.Titel, movie.MovieID); customer.customerRentedMovies.Add(rentedMovie); break; } else { Console.WriteLine("No movie with that titel and ID!"); } } break; } else { Console.WriteLine("No customer with that ID and name"); } } }

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  • Nullable<T> as a parameter

    - by ferch
    I alredy have this: public static object GetDBValue(object ObjectEvaluated) { if (ObjectEvaluated == null) return DBNull.Value; else return ObjectEvaluated; } used like: List<SqlParameter> Params = new List<SqlParameter>(); Params.Add(new SqlParameter("@EntityType", GetDBValue(EntityType))); Now i wanted to keep the same interface but extend that to use it with nullable public static object GetDBValue(int? ObjectEvaluated) { if (ObjectEvaluated.HasValue) return ObjectEvaluated.Value; else return DBNull.Value; } public static object GetDBValue(DateTime? ObjectEvaluated) {...} but i want only 1 function GetDBValue for nullables. How do I do that and keep the call as is is? Is that possible at all? I can make it work like: public static object GetDBValue<T>(Nullable<T> ObjectEvaluated) where T : struct { if (ObjectEvaluated.HasValue) return ObjectEvaluated.Value; else return DBNull.Value; } But the call changes to: Params.Add(new SqlParameter("@EntityID ", GetDBValue<int>(EntityID)));

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  • Put/Post json not working with ODataController if Model has Int64

    - by daryl
    I have this Data Object with an Int64 column: [TableAttribute(Name="dbo.vw_RelationLineOfBusiness")] [DataServiceKey("ProviderRelationLobId")] public partial class RelationLineOfBusiness { #region Column Mappings private System.Guid _Lineofbusiness; private System.String _ContractNumber; private System.Nullable<System.Int32> _ProviderType; private System.String _InsuredProviderType; private System.Guid _ProviderRelationLobId; private System.String _LineOfBusinessDesc; private System.String _CultureCode; private System.String _ContractDesc; private System.Nullable<System.Guid> _ProviderRelationKey; private System.String _ProviderRelationNbr; **private System.Int64 _AssignedNbr;** When I post/Put object through my OData controller using HttpClient and NewtsonSoft: partial class RelationLineOfBusinessController : ODataController { public HttpResponseMessage PutRelationLineOfBusiness([FromODataUri] System.Guid key, Invidasys.VidaPro.Model.RelationLineOfBusiness entity) the entity object is null and the error in my modelstate : "Cannot convert a primitive value to the expected type 'Edm.Int64'. See the inner exception for more details." I noticed when I do a get on my object using the below URL: Invidasys.Rest.Service/VidaPro/RelationLineOfBusiness(guid'c6824edc-23b4-4f76-a777-108d482c0fee') my json looks like the following - I noticed that the AssignedNbr is treated as a string. { "odata.metadata":"Invidasys.Rest.Service/VIDAPro/$metadata#RelationLineOfBusiness/@Element", "Lineofbusiness":"ba129c95-c5bb-4e40-993e-c28ca86fffe4","ContractNumber":null,"ProviderType":null, "InsuredProviderType":"PCP","ProviderRelationLobId":"c6824edc-23b4-4f76-a777-108d482c0fee", "LineOfBusinessDesc":"MEDICAID","CultureCode":"en-US","ContractDesc":null, "ProviderRelationKey":"a2d3b61f-3d76-46f4-9887-f2b0c8966914","ProviderRelationNbr":"4565454645", "AssignedNbr":"1000000045","Ispar":true,"ProviderTypeDesc":null,"InsuredProviderTypeDesc":"Primary Care Physician", "StartDate":"2012-01-01T00:00:00","EndDate":"2014-01-01T00:00:00","Created":"2014-06-13T10:59:33.567", "CreatedBy":"Michael","Updated":"2014-06-13T10:59:33.567","UpdatedBy":"Michael" } When I do a PUT with httpclient the JSON is showing up in my restful services as the following and the json for the AssignedNbr column is not in quotes which results in the restful services failing to build the JSON back to an object. I played with the JSON and put the AssignedNbr in quotes and the request goes through correctly. {"AssignedNbr":1000000045,"ContractDesc":null,"ContractNumber":null,"Created":"/Date(1402682373567-0700)/", "CreatedBy":"Michael","CultureCode":"en-US","EndDate":"/Date(1388559600000-0700)/","InsuredProviderType":"PCP", "InsuredProviderTypeDesc":"Primary Care Physician","Ispar":true,"LineOfBusinessDesc":"MEDICAID", "Lineofbusiness":"ba129c95-c5bb-4e40-993e-c28ca86fffe4","ProviderRelationKey":"a2d3b61f-3d76-46f4-9887-f2b0c8966914", "ProviderRelationLobId":"c6824edc-23b4-4f76-a777-108d482c0fee","ProviderRelationNbr":"4565454645","ProviderType":null, "ProviderTypeDesc":null,"StartDate":"/Date(1325401200000-0700)/","Updated":"/Date(1408374995760-0700)/","UpdatedBy":"ED"} The reason we wanted to expose our business model as restful services was to hide any data validation and expose all our databases in format that is easy to develop against. I looked at the DataServiceContext to see if it would work and it does but it uses XML to communicate between the restful services and the client. Which would work but DataServiceContext does not give the level of messaging that HttpRequestMessage/HttpResponseMessage gives me for informing users on the errors/missing information with their post. We are planning on supporting multiple devices from our restful services platform but that requires that I can use NewtonSoft Json as well as Microsoft's DataContractJsonSerializer if need be. My question is for a restful service standpoint - is there a way I can configure/code the restful services to take in the AssignedNbr as in JSON as without the quotes. Or from a JSON standpoint is their a way I can get the JSON built without getting into the serializing business nor do I want our clients to have deal with custom serializers if they want to write their own apps against our restful services. Any suggestions? Thanks.

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  • How to best propagate changes upwards a hierarchical structure for binding?

    - by H.B.
    If i have a folder-like structure that uses the composite design pattern and i bind the root folder to a TreeView. It would be quite useful if i can display certain properties that are being accumulated from the folder's contents. The question is, how do i best inform the folder that changes occurred in a child-element so that the accumulative properties get updated? The context in which i need this is a small RSS-FeedReader i am trying to make. This are the most important objects and aspects of my model: Composite interface: public interface IFeedComposite : INotifyPropertyChanged { string Title { get; set; } int UnreadFeedItemsCount { get; } ObservableCollection<FeedItem> FeedItems { get; } } FeedComposite (aka Folder) public class FeedComposite : BindableObject, IFeedComposite { private string title = ""; public string Title { get { return title; } set { title = value; NotifyPropertyChanged("Title"); } } private ObservableCollection<IFeedComposite> children = new ObservableCollection<IFeedComposite>(); public ObservableCollection<IFeedComposite> Children { get { return children; } set { children.Clear(); foreach (IFeedComposite item in value) { children.Add(item); } NotifyPropertyChanged("Children"); } } public FeedComposite() { } public FeedComposite(string title) { Title = title; } public ObservableCollection<FeedItem> FeedItems { get { ObservableCollection<FeedItem> feedItems = new ObservableCollection<FeedItem>(); foreach (IFeedComposite child in Children) { foreach (FeedItem item in child.FeedItems) { feedItems.Add(item); } } return feedItems; } } public int UnreadFeedItemsCount { get { return (from i in FeedItems where i.IsUnread select i).Count(); } } Feed: public class Feed : BindableObject, IFeedComposite { private string url = ""; public string Url { get { return url; } set { url = value; NotifyPropertyChanged("Url"); } } ... private ObservableCollection<FeedItem> feedItems = new ObservableCollection<FeedItem>(); public ObservableCollection<FeedItem> FeedItems { get { return feedItems; } set { feedItems.Clear(); foreach (FeedItem item in value) { AddFeedItem(item); } NotifyPropertyChanged("Items"); } } public int UnreadFeedItemsCount { get { return (from i in FeedItems where i.IsUnread select i).Count(); } } public Feed() { } public Feed(string url) { Url = url; } Ok, so here's the thing, if i bind a TextBlock.Text to the UnreadFeedItemsCount there won't be simple notifications when an item is marked unread, so one of my approaches has been to handle the PropertyChanged event of every FeedItem and if the IsUnread-Property is changed i have my Feed make a notification that the property UnreadFeedItemsCount has been changed. With this approach i also need to handle all PropertyChanged events of all Feeds and FeedComposites in Children of FeedComposite, from the sound of it, it should be obvious that this is not such a very good idea, you need to be very careful that items never get added or removed to any collection without having attached the PropertyChanged event handler first and things like that. Also: What do i do with the CollectionChanged-Events which necessarily also cause a change in the sum of the unread items count? Sounds like more event handling fun. It is such a mess, it would be great if anyone has an elegant solution to this since i don't want the feed-reader to end up as awful as my first attempt years ago when i didn't even know about DataBinding...

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  • Question about Virtual Inheritance hierarchy

    - by Summer_More_More_Tea
    Hi there: I encounter this problem when tackling with virtual inheritance. I remember that in a non-virtual inheritance hierarchy, object of sub-class hold an object of its direct super-class. What about virtual inheritance? In this situation, does object of sub-class hold an object of its super-class directly or just hold a pointer pointing to an object of its super-class? By the way, why the output of the following code is: sizeof(A): 8 sizeof(B): 20 sizeof(C): 20 sizeof(C): 36 Code: #include <iostream> using namespace std; class A{ char k[ 3 ]; public: virtual void a(){}; }; class B : public virtual A{ char j[ 3 ]; public: virtual void b(){}; }; class C : public virtual B{ char i[ 3 ]; public: virtual void c(){}; }; class D : public B, public C{ char h[ 3 ]; public: virtual void d(){}; }; int main( int argc, char *argv[] ){ cout << "sizeof(A): " << sizeof( A ) << endl; cout << "sizeof(B): " << sizeof( B ) << endl; cout << "sizeof(C): " << sizeof( C ) << endl; cout << "sizeof(D): " << sizeof( D ) << endl; return 0; } Thanks in advance. Kind regards.

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  • Why is the dictionary debug visualizer less useful in Visual Studio 2010?

    - by Kevin
    I was debugging in Visual Studio 2010, which we just installed and trying to look at a dictionary in the quick watch window. I see Keys and Values, but drilling into those shows the Count and Non-Public members, Non-Public members continues the trail and I never see the values in the dictionary. I can run test.Take(10) and see the values, but why should I have to do that. I don't have VS 2008 installed anymore to compare, but it seems that I could debug a dictionary much easier. Why is it this way now? Is it just a setting I set somehow on my machine? Test code: Dictionary<string, string> test = new Dictionary<string, string>(); test.Add("a", "b");

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