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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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• How do I add information to an exception message without changing its class in ruby?

  - by Andrew Grimm

  How do I add information to an exception message without changing its class in ruby? The approach I'm currently using is strings.each_with_index do |string, i| begin do_risky_operation(string) rescue raise $!.class, "Problem with string number #{i}: #{$!}" end end Is there a better way?

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• Core Data - Relationship to dissimilar entities

  - by carotene

  Suppose I have the following data model: Entity Person Attribute name String Attribute personType String Attribute dailyRecords Entity CarpenterDailyRecord Attribute numberOfNailsHammered Int Attribute picNameOfFinishedCabinet String Entity WindowWasherDailyRecord Attribute nameOfBuildingWashed String Attribute numberOfWindowsWashed Int I would like to establish a to-many relationship between the Person.dailyRecords and 1 of the daily record entities (which changes depending on the person type). Of course, i could create a CarpenterPerson and WindowWasher entity which each points to it's unique daily record structure, but i have to group people together in my app somehow. so if i do a Group Entity: Entity Group Attribute people array i'm still stuck. how do i point to multiple & different Person entities? There must be an obvious answer, it's just i'm so new to all of this. thanks!

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• Joda Time cannot subtract one hour

  - by Leoa

  In my android program, I have a spinner that allows the user to select different times. Each selection is processed with Joda time to subtract the minutes. It works fine for minutes 0 to 59 and 61 and greater. However, when 60 minutes is subtracted, the time is not updated, and the original time is shown. How do I get Joda time to subtract 60 minutes? Spinner: public class MyOnItemSelectedListener implements OnItemSelectedListener { public void onItemSelected(AdapterView<?> parent, View view, int pos, long id1) { String mins = parent.getItemAtPosition(pos).toString(); int intmins=0; // process user's selection of alert time if(mins.equals("5 minutes")){intmins = 5;} if(mins.equals("10 minutes")){intmins = 10;} if(mins.equals("20 minutes")){intmins = 20;} if(mins.equals("30 minutes")){intmins = 30;} if(mins.equals("40 minutes")){intmins = 40;} if(mins.equals("50 minutes")){intmins = 50;} if(mins.equals("60 minutes")){intmins = 60;} if(mins.equals("120 minutes")){intmins = 120;} String stringMinutes=""+intmins; setAlarm(intmins, stringMinutes); } else { } public void onNothingSelected(AdapterView parent) { mLocationDisplay.setText(" " + location); } } public void setAlarm(int intmins, String mins) { // based alarm time on start time of event. TODO get info from database. String currentDate; SimpleDateFormat myFormat = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss"); Date date1 = null; DateTime dt; currentDate = eventdate + " " + startTimeMilitary;// startTimeMilitary; try { date1 = myFormat.parse(currentDate); } catch (ParseException e) { // TODO Auto-generated catch block e.printStackTrace(); } dt = new DateTime(date1); long dateInMillis = dt.getMillis(); String sDateInMillis = Long.toString(dateInMillis); // subtract the selected time from the event's start time String newAlertTime = subtractTime(dt, intmins); newAlertTime = subtractTime(dt, intmins); //......}

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• mocking command object in grails controller results in hasErrors() return false no matter what! Plea

  - by egervari

  I have a controller that uses a command object in a controller action. When mocking this command object in a grails' controller unit test, the hasErrors() method always returns false, even when I am purposefully violating its constraints. def save = { RegistrationForm form -> if(form.hasErrors()) { // code block never gets executed } else { // code block always gets executed } } In the test itself, I do this: mockCommandObject(RegistrationForm) def form = new RegistrationForm(emailAddress: "ken.bad@gmail", password: "secret", confirmPassword: "wrong") controller.save(form) I am purposefully giving it a bad email address, and I am making sure the password and the confirmPassword properties are different. In this case, hasErrors() should return true... but it doesn't. I don't know how my testing can be any where reliable if such a basic thing does not work :/ Here is the RegistrationForm class, so you can see the constraints I am using: class RegistrationForm { def springSecurityService String emailAddress String password String confirmPassword String getEncryptedPassword() { springSecurityService.encodePassword(password) } static constraints = { emailAddress(blank: false, email: true) password(blank: false, minSize:4, maxSize: 10) confirmPassword(blank: false, validator: { confirmPassword, form -> confirmPassword == form.password }) } }

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• Find substring ignoring specified characters

  - by Fredy Treboux

  Hello, please, does any of you knows and can share an easy/clean way to find a substring within a string, but ignoring some specified characters to find it. I think an example would explain things better: string: "Hello, -this- is a string" substring to find: "Hello this" chars to ignore: "," and "-" found the substring, result: "Hello, -this" Using Regex it's not a requirement for me, just added the tag because it feels related.

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• C# - Dictionary with generic array as value

  - by alhazen

  In my class, I want to use a dictionary with the following declaration: Dictionary<string, T[]> Since the operations of my class are exactly the same for all generic types, I do not wish to define my class as generic (which means I would have to create a separate instance of my class for each generic type I insert into the dictionary ?). One alternative I'm attempting is to use Dictionary<string, object> instead: public void Add<T>(string str, T value) { // Assuming key already exists var array = (T[]) dictionary[str]; array[0] = value; } However, when iterating over the dictionary, how do I cast the object value back to an array ? foreach(string strKey in dictionary.Keys) { var array = (T[]) dictionary[strKey]; // How to cast here ? //... array[0] = default(T); } Thanks.

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• JAVA Procedure Error

  - by Sam....

  java.sql.SQLException: [Microsoft][SQLServer 2000 Driver for JDBC][SQLServer]Procedure 'STP_Insert_tblReceipt' expects parameter '@CPVFlag', which was not supplied. I m getting error at This Point when trying to call procedure... Everything is perfect ,,,Count of Question marks are similar to parameter provided cs = conn.prepareCall("{call STP_Insert_tblReceipt(?,?,?, ?,?,?, ?,?,?, ?,?,?, ?,?,?, ?,?,?, ?,?,?, ?,?,?, ?,?,?)}"); // cs = conn.prepareCall("{call STP_Receipt_Form_Insertion_Trial(?,?,?, ?,?,?, ?,?,?, ?,?,?, ?)}"); cs.setLong(1, Long.parseLong(txtMobileNo.getText())); cs.setString(2, String.valueOf(cboDistributor.getSelectedItem())); cs.setLong(3, Long.parseLong(txtBoxNo.getText())); cs.setInt(4, Integer.parseInt(txtFileNo.getText())); cs.setString(5, pickUp_date); cs.setString(6, rec_date); cs.setString(7, String.valueOf(cmbCtrlNo.getSelectedItem())); cs.setString(8, UserName); cs.setString(9, rec_date); cs.setString(10, RegionLocation); cs.setString(11, txtRemark.getText().trim()); cs.setString(12, txtSimNo.getText().trim()); cs.setInt(13, 2); cs.setString(14, String.valueOf(cmbAryanRegion.getSelectedItem())); cs.setString(15, String.valueOf(cboPickUpType.getSelectedItem())); cs.setString(16, String.valueOf(txtCafNo.getText())); cs.setString(17, distributorId); //cs.setString(18, circleName); cs.setString(18, cboCircle.getSelectedItem().toString()); cs.registerOutParameter(19, java.sql.Types.INTEGER); cs.setString(20, auditorName); cs.setString(21, retailerName); cs.setString(22, retailerCode); cs.setInt(23, mappedFlag); //cs.setString(24, distCode); cs.setString(24, cboDistCode.getSelectedItem().toString()); //cs.setString(25, zoneName); cs.setString(25, cboZone.getSelectedItem().toString()); cs.setString(26, comment); **cs.setInt(27, 1);** **this is for CPV Flag** After this cs.execute();

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• Populate asp.net MVC Index page with data from the database

  - by Sunil Ramu

  I have a web application in which I need to fetch data from the database and display in the index page. As you know, asp.net mvc has given options to edit delete etc... I need to populate the page using the conventional DB way and it uses a stored procedure to retrieve results. I dont want to use LINQ. This is my model entity class using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace LogMVCApp.Models { public class Property { public int Id { get; set; } public string LogInId { get; set; } public string Username { get; set; } public string Action { get; set; } public string Information { get; set; } public bool Passed{get; set; } public string LogType { get; set; } } } and I need to retrieve data using something like this... var conString = ConfigurationManager.ConnectionStrings["connection"].ToString(); var conn = new SqlConnection(conString); var command = new SqlCommand("LogInsert", conn){CommandType=CommandType.StoredProcedure};

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• validate constructor arguments or method parameters with annotations, and let them throw an exceptio

  - by marius

  I am validating constructor and method arguments, as I want to the software, especially the model part of it, to fail fast. As a result, constructor code often looks like this public MyModelClass(String arg1, String arg2, OtherModelClass otherModelInstance) { if(arg1 == null) { throw new IllegalArgumentsException("arg1 must not be null"); } // further validation of constraints... // actual constructor code... } Is there a way to do that with an annotation driven approach? Something like: public MyModelClass(@NotNull(raise=IllegalArgumentException.class, message="arg1 must not be null") String arg1, @NotNull(raise=IllegalArgumentException.class) String arg2, OtherModelClass otherModelInstance) { // actual constructor code... } In my eyes this would make the actual code a lot more readable. In understand that there are annotations in order to support IDE validation (like the existing @NotNull annotation). Thank you very much for your help.

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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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• about option buttons in User form

  - by Mars

  I have a question: I need to create a user form that contain that usual OK and Cancel Buttons. It also should contain two sets of Options buttons, each set placed inside a frame. The captions on the first set should be basketball, baseball, football, the captions on the second set should be watch on TV and Go to games. I need to write the event handlers and code in a module so that when the program runs, the user sees the form. If the user makes a couple of choices and clicks OK, he should see a message like "Your favorite sport is basketball, and you usually watch on TV." If the user clicks Cancel, the message "Sorry you don't want to play" should appear. I think I almost have it working, but I don't know why I cannot successfully execute the Macro. My Code is : Option Explicit Private Sub CommandButton2_Click() MsgBox ("sorry if you don't want to play") End Sub Private Sub commandbuttons_Click() Dim optbasket As String, optbaseball As String, optfootball As String Dim optwog As String, optgtg As String Select Case True Case optbasket optbasket = True Case optbaseball optbaseball = True Case optfootball optfootball = True End Select If optwog Then optwog = True Else optgtg = True End If btnok = MsgBox("you favorite sport is " & Frame1.Value & "you usually " & Frame2.Value & ",") End Sub Private Sub OptionButton1_Click() End Sub Private Sub btmcancel_Click() End Sub Private Sub btnok_Click() End Sub Private Sub Frame1_Click() End Sub Private Sub Frame2_Click() End Sub Private Sub optbaseball_Click() End Sub Private Sub optbasketball_Click() End Sub Private Sub optfootball_Click() End Sub Thank you very much!!!

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• Javascript culture always en-us

  - by LoveMeSomeCode

  I'm not sure if I understand this code or if I'm using it right, but I was under the impression that in an ASP.NET 2.0 AJAX website I could run javascript like: var c = Sys.CultureInfo.CurrentCulture and it would give me the culture/language settings the user had specified in their browser at the time of the visit. However, for me, it always comes back 'en-US' no matter what language I pick in firefox or IE. This serverside code however: string[] languages = HttpContext.Current.Request.UserLanguages; if (languages == null || languages.Length == 0) return null; try { string language = languages[0].ToLowerInvariant().Trim(); return CultureInfo.CreateSpecificCulture(language); } catch (ArgumentException) { return null; } does return the language I have currently set. But I need to do this clientside, because I need to parse a string into a datetime and do some validations before I postback, and the string could be a MM/DD/YYYY or DD/MM/YYYY, or some other such thing. What am I missing?

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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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• Adding defaults and indexes to a script/generate command in a Rails Template?

  - by charliepark

  I'm trying to set up a Rails Template that would allow for comprehensive set-up of a specific Rails app. Using Pratik Naik's overview (http://m.onkey.org/2008/12/4/rails-templates), I was able to set up a couple of scaffolds and models, with a line that looks something like this ... generate("scaffold", "post", "title:string", "body:string") I'm now trying to add in Delayed Jobs, which normally has a migration file that looks like this: create_table :delayed_jobs, :force => true do |table| table.integer :priority, :default => 0 # Allows some jobs to jump to the front of the queue table.integer :attempts, :default => 0 # Provides for retries, but still fail eventually. table.text :handler # YAML-encoded string of the object that will do work table.text :last_error # reason for last failure (See Note below) table.datetime :run_at # When to run. Could be Time.now for immediately, or sometime in the future. table.datetime :locked_at # Set when a client is working on this object table.datetime :failed_at # Set when all retries have failed (actually, by default, the record is deleted instead) table.string :locked_by # Who is working on this object (if locked) table.timestamps end So, what I'm trying to do with the Rails template, is to add in that :default = 0 into the master template file. I know that the rest of the template's command should look like this: generate("migration", "createDelayedJobs", "priority:integer", "attempts:integer", "handler:text", "last_error:text", "run_at:datetime", "locked_at:datetime", "failed_at:datetime", "locked_by:string") Where would I put (or, rather, what is the syntax to add) the :default values in that? And if I wanted to add an index, what's the best way to do that?

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• Automatically Word-Wrapping Text To A Print Page?

  - by sooprise

  I have some code that prints a string, but if the string is say: "Blah blah blah"... and there are no line breaks, the text occupies a single line. I would like to be able to shape the string so it word wraps to the dimensions of the paper. private void PrintIt(){ PrintDocument document = new PrintDocument(); document.PrintPage += (sender, e) => Document_PrintText(e, inputString); document.Print(); } static private void Document_PrintText(PrintPageEventArgs e, string inputString) { e.Graphics.DrawString(inputString, new Font("Courier New", 12), Brushes.Black, 0, 0); } I suppose I could figure out the length of a character, and wrap the text manually, but if there is a built in way to do this, I'd rather do that. Thanks!

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• How to extract data from a text file

  - by šljaker

  I need to parse some large text file and extract Display name and area code only if it matches the following pattern: Line starts with display name (any number of words) Followed by 6 digits (can contain spaces) Followed by #text tag e.g. John doe 123 456 #text some text Display name: John doe Area code: 123 456 Test 123456 #text Display name: Test Area code: 123456 Test 123 #test Invalid, area code contains only 3 digits Test 123456 #test1 Invalid, contains invalid tag Test 123g45 #test Invalid, area code contains letters etc. I know how to open the text file and read it line by line, but having trouble with writing the regular expression. Any help would be greatly appreciated! edit: I have tried this: private static void Main(string[] args) { string text = "John Doe 123 45 #text Lorem ipsum dolor :)"; string pattern = @"(\w+)*([0-9]{2,5}).([0-9]{2,5}).#text"; Match match = Regex.Match(text, pattern, RegexOptions.IgnoreCase); if (match.Success) { string key = match.Groups[0].Value; Console.WriteLine(key); } }

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• C++ data member initializer is not allowed

  - by user1435915

  I totally new to C++ so bear with me. I want to make a class with a static array, and access to this array from the main. Here is what i want to do in C#. namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Class a = new Class(); Console.WriteLine(a.arr[1]); } } } ===================== namespace ConsoleApplication1 { class Class { public static string[] s_strHands = new string[]{"one","two","three"}; } } Here is what i have tried: // justfoolin.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include <string> #include <iostream> using namespace std; class Class { public: static string arr[3] = {"one", "two", "three"}; }; int _tmain(int argc, _TCHAR* argv[]) { Class x; cout << x.arr[2] << endl; return 0; } But i got: IntelliSense: data member initializer is not allowed

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• Regexp look-behind to match internet speeds

  - by Sandman

  So the user may search for "10 mbit" after which I want to capture the "10" so I can use it in a speed-search rather than a string-search. This isn't a problem, the below regexp does this fine: if (preg_match("/(\d+)\smbit/", $string)){ ... } But, the user may search for something like "10/10 mbit" or "10-100 mbit". I don't want to match those with the above regexp - they should be handled in another fashion. So I would like a regexp that matches "10 mbit" if the number is all-numeric as a whole word (i.e. contained by whitespace, newline or lineend/linestart) Using lookbehind, I did this: if (preg_match("#(?<!/)(\d+)\s+mbit#i", $string)){ Just to catch those that doesn't have "/" before them, but this matched true for this string: "10/10 mbit" so I'm obviously doing something wrong here, but what?

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• replace values in form.data when form fails validation

  - by John

  Hi I have a form field which requires a json object as its value when it is rendered. When the form is submitted it returns a comma seperated string of ids as its value (not a json string). however if the form does not validate i want to turn this string of ids back into a json string so it will display properly (is uses jquery to render the json object correctly). how would i do this? I was thinking of overwriting the form.clean method but when I tried to change self.data['fieldname'] I got the error 'This QueryDict instance is immutable' and when i tried to change self.cleaned_data['fieldname'] it didn't make a difference to the value of the field. Thanks

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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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• How to use Comparator in Java to sort

  - by Dan

  I learned how to use the comparable but I'm having difficulty with the Comparator. I am having a error in my code: Exception in thread "main" java.lang.ClassCastException: New.People cannot be cast to java.lang.Comparable at java.util.Arrays.mergeSort(Unknown Source) at java.util.Arrays.sort(Unknown Source) at java.util.Collections.sort(Unknown Source) at New.TestPeople.main(TestPeople.java:18) Here is my code: import java.util.Comparator; public class People implements Comparator{ private int id; private String info; private double price; public People(int newid, String newinfo, double newprice){ setid(newid); setinfo(newinfo); setprice(newprice); } public int getid() { return id; } public void setid(int id) { this.id = id; } public String getinfo() { return info; } public void setinfo(String info) { this.info = info; } public double getprice() { return price; } public void setprice(double price) { this.price = price; } public int compare(Object obj1, Object obj2) { Integer p1 = ((People)obj1).getid(); Integer p2 = ((People)obj2).getid(); if (p1 p2 ){ return 1; } else if (p1 < p2){ return -1; } else return 0; } } import java.util.ArrayList; import java.util.Collections; public class TestPeople { public static void main(String[] args) { ArrayList peps = new ArrayList(); peps.add(new People(123, "M", 14.25)); peps.add(new People(234, "M", 6.21)); peps.add(new People(362, "F", 9.23)); peps.add(new People(111, "M", 65.99)); peps.add(new People(535, "F", 9.23)); Collections.sort(peps); for(int i=0;i I believe it has to do something with the casting in the compare method but I was playing around with it and still could not find the solution

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• ASP.NET MVC 2 - Checkboxes

  - by Jay

  I'm using string[] roles = Roles.GetAllRoles() to get a string[] of all the ASP.NET membership roles for my application. I'm sending the roles to my view in ViewData and using a foreach to create a set of Checkboxes using <%: Html.CheckBox("RoleCheckBox") %>. There are 3 roles and my view does render 3 checkboxes. When I do a View/Source, I see the checkboxes and their corresponding hidden tags. They all have the same, so there are 6 tags with the name "RoleCheckBox" - 3 that render the checkboxes and 3 that are hidden. The problem comes when I post the form back to my controller and bind the results - something like public ActionResult Create(Person person, string[] RoleCheckBox). I get FOUR strings and I have no idea where the fourth string ("false") is coming from. I could do some testing by trying various combinations of checks to see which one (hopefully) doesn't change and ignore it but that's just ugly. Does anyone know why this would be happening? Thanks, Jay

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• Question regarding common class

  - by Rocky Singh

  I have following two classes: public class A : System.Web.UI.WebControls.Button { public virtual string X { get { object obj = ViewState["X"]; if (obj != null) return (string)obj; return null; } set { ViewState["X"] = value; } } protected override void OnLoad(EventArgs e) { X=2; } } and public class B : System.Web.UI.WebControls.TextBox { public virtual string X { get { object obj = ViewState["X"]; if (obj != null) return (string)obj; return null; } set { ViewState["X"] = value; } } protected override void OnLoad(EventArgs e) { X=2; } } As you must be seeing the class A and B have exactly the same code , my question is how can I make a common class for it and use these two classes.

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• LINQ Except operator and object equality

  - by Abhijeet Patel

  Here is an interesting issue I noticed when using the Except Operator: I have list of users from which I want to exclude some users: The list of users is coming from an XML file: The code goes like this: interface IUser { int ID { get; set; } string Name { get; set; } } class User: IUser { #region IUser Members public int ID { get; set; } public string Name { get; set; } #endregion public override string ToString() { return ID + ":" +Name; } public static IEnumerable<IUser> GetMatchingUsers(IEnumerable<IUser> users) { IEnumerable<IUser> localList = new List<User> { new User{ ID=4, Name="James"}, new User{ ID=5, Name="Tom"} }.OfType<IUser>(); var matches = from u in users join lu in localList on u.ID equals lu.ID select u; return matches; } } class Program { static void Main(string[] args) { XDocument doc = XDocument.Load("Users.xml"); IEnumerable<IUser> users = doc.Element("Users").Elements("User").Select (u => new User { ID = (int)u.Attribute("id"), Name = (string)u.Attribute("name") } ).OfType<IUser>(); //still a query, objects have not been materialized var matches = User.GetMatchingUsers(users); var excludes = users.Except(matches); // excludes should contain 6 users but here it contains 8 users } } When I call User.GetMatchingUsers(users) I get 2 matches as expected. The issue is that when I call users.Except(matches) The matching users are not being excluded at all! I am expecting 6 users ut "excludes" contains all 8 users instead. Since all I'm doing in GetMatchingUsers(IEnumerable users) is taking the IEnumerable and just returning the IUsers whose ID's match( 2 IUsers in this case), my understanding is that by default "Except" will use reference equality for comparing the objects to be excluded. Is this not how "Except" behaves? What is even more interesting is that if I materialize the objects using .ToList() and then get the matching users, and call "Except", everything works as expected! Like so: IEnumerable users = doc.Element("Users").Elements("User").Select (u = new User { ID = (int)u.Attribute("id"), Name = (string)u.Attribute("name") } ).OfType().ToList(); //explicity materializing all objects by calling ToList() var matches = User.GetMatchingUsers(users); var excludes = users.Except(matches); // excludes now contains 6 users as expected I don't see why I should need to materialize objects for calling "Except" given that its defined on IEnumerable? Any suggesstions / insights would be much appreciated.

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