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• to-many Core Data fetch request behaves oddly with a new store

  - by Giao

  I have two entities, Department and Person. Department has a to-many relationship to Person. The Person entity has a hireDate property. I'm using the predicate "count(person) = 0 OR none person.hireDate %@" to find Departments without any Persons in them or Departments that haven't hired anyone since a recent date. When the app first starts up (new user experience) and Departments are inserted and no Person have been inserted, the fetch request with this predicate returns nothing. However, if I create insert a new Person entity and delete it, then save the store, the fetch request will return all the Departments. I've found a work around where, I just insert a new Person and delete it, then save the store, the fetch request as I expected it to work. I've found that inserting a new Person and deleting it without saving will not correct the problem. Is this a bug with Core Data or is this a bug with how I've designed my app?

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• Nested class with hidden constructor impossible in c#?

  - by luckyluke

  I' ve been doing some programming lately and faced an issue which i found weird in c#. (at least for me) public class Foo { //whatever public class FooSpecificCollection : List<Bar> { //implementation details } public FooSpecificCollection GetFoosStuff() { //return the collection } } I want the consumer of Foo to be able to obtain a reference to FooSpecificCollection, even perform some operations on it. Maybe even set it to some other property of Foo or smth like that, but not To be able to CREATE an instance of this class. (the only class that should be able to instatiate this collection should be Foo. Is my request really that far-fetched? I know that people way smarter defined c# but shouldn't there be such an option that a parent class can create a nested class instance but nobody else can't. So far I created a solution to make an abstract class, or interface available through the property and implement a concrete private class that is not available anywhere else. Is this a correct way to handle such a situation.?

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• Custom Memory Allocator for STL map

  - by Prasoon Tiwari

  This question is about construction of instances of custom allocator during insertion into a std::map. Here is a custom allocator for std::map<int,int> along with a small program that uses it: #include <stddef.h> #include <stdio.h> #include <map> #include <typeinfo> class MyPool { public: void * GetNext() { return malloc(24); } void Free(void *ptr) { free(ptr); } }; template<typename T> class MyPoolAlloc { public: static MyPool *pMyPool; typedef size_t size_type; typedef ptrdiff_t difference_type; typedef T* pointer; typedef const T* const_pointer; typedef T& reference; typedef const T& const_reference; typedef T value_type; template<typename X> struct rebind { typedef MyPoolAlloc<X> other; }; MyPoolAlloc() throw() { printf("-------Alloc--CONSTRUCTOR--------%08x %32s\n", this, typeid(T).name()); } MyPoolAlloc(const MyPoolAlloc&) throw() { printf(" Copy Constructor ---------------%08x %32s\n", this, typeid(T).name()); } template<typename X> MyPoolAlloc(const MyPoolAlloc<X>&) throw() { printf(" Construct T Alloc from X Alloc--%08x %32s %32s\n", this, typeid(T).name(), typeid(X).name()); } ~MyPoolAlloc() throw() { printf(" Destructor ---------------------%08x %32s\n", this, typeid(T).name()); }; pointer address(reference __x) const { return &__x; } const_pointer address(const_reference __x) const { return &__x; } pointer allocate(size_type __n, const void * hint = 0) { if (__n != 1) perror("MyPoolAlloc::allocate: __n is not 1.\n"); if (NULL == pMyPool) { pMyPool = new MyPool(); printf("======>Creating a new pool object.\n"); } return reinterpret_cast<T*>(pMyPool->GetNext()); } //__p is not permitted to be a null pointer void deallocate(pointer __p, size_type __n) { pMyPool->Free(reinterpret_cast<void *>(__p)); } size_type max_size() const throw() { return size_t(-1) / sizeof(T); } void construct(pointer __p, const T& __val) { printf("+++++++ %08x %s.\n", __p, typeid(T).name()); ::new(__p) T(__val); } void destroy(pointer __p) { printf("-+-+-+- %08x.\n", __p); __p->~T(); } }; template<typename T> inline bool operator==(const MyPoolAlloc<T>&, const MyPoolAlloc<T>&) { return true; } template<typename T> inline bool operator!=(const MyPoolAlloc<T>&, const MyPoolAlloc<T>&) { return false; } template<typename T> MyPool* MyPoolAlloc<T>::pMyPool = NULL; int main(int argc, char *argv[]) { std::map<int, int, std::less<int>, MyPoolAlloc<std::pair<const int,int> > > m; //random insertions in the map m.insert(std::pair<int,int>(1,2)); m[5] = 7; m[8] = 11; printf("======>End of map insertions.\n"); return 0; } Here is the output of this program: -------Alloc--CONSTRUCTOR--------bffcdaa6 St4pairIKiiE Construct T Alloc from X Alloc--bffcda77 St13_Rb_tree_nodeISt4pairIKiiEE St4pairIKiiE Copy Constructor ---------------bffcdad8 St13_Rb_tree_nodeISt4pairIKiiEE Destructor ---------------------bffcda77 St13_Rb_tree_nodeISt4pairIKiiEE Destructor ---------------------bffcdaa6 St4pairIKiiE ======Creating a new pool object. Construct T Alloc from X Alloc--bffcd9df St4pairIKiiE St13_Rb_tree_nodeISt4pairIKiiEE +++++++ 0985d028 St4pairIKiiE. Destructor ---------------------bffcd9df St4pairIKiiE Construct T Alloc from X Alloc--bffcd95f St4pairIKiiE St13_Rb_tree_nodeISt4pairIKiiEE +++++++ 0985d048 St4pairIKiiE. Destructor ---------------------bffcd95f St4pairIKiiE Construct T Alloc from X Alloc--bffcd95f St4pairIKiiE St13_Rb_tree_nodeISt4pairIKiiEE +++++++ 0985d068 St4pairIKiiE. Destructor ---------------------bffcd95f St4pairIKiiE ======End of map insertions. Construct T Alloc from X Alloc--bffcda23 St4pairIKiiE St13_Rb_tree_nodeISt4pairIKiiEE -+-+-+- 0985d068. Destructor ---------------------bffcda23 St4pairIKiiE Construct T Alloc from X Alloc--bffcda43 St4pairIKiiE St13_Rb_tree_nodeISt4pairIKiiEE -+-+-+- 0985d048. Destructor ---------------------bffcda43 St4pairIKiiE Construct T Alloc from X Alloc--bffcda43 St4pairIKiiE St13_Rb_tree_nodeISt4pairIKiiEE -+-+-+- 0985d028. Destructor ---------------------bffcda43 St4pairIKiiE Destructor ---------------------bffcdad8 St13_Rb_tree_nodeISt4pairIKiiEE Last two columns of the output show that an allocator for std::pair<const int, int> is constructed everytime there is a insertion into the map. Why is this necessary? Is there a way to suppress this? Thanks! Edit: This code tested on x86 machine with g++ version 4.1.2. If you wish to run it on a 64-bit machine, you'll have to change at least the line return malloc(24). Changing to return malloc(48) should work.

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• using OOoWrite, i would like to add custom html elements

  - by romunov

  I have 35 pages list of scientific references. In order to upload them to a webpage, I would like to add custom fields before and after each reference. I would also like to find italicized text and add around it. For instance, I would like this paragraph Alouf N., 1973. Biotope et description de Niphargus altagahizi n. sp., Amphipode Gammaridé souterrain du Liban, International Journal of Speleology 5: 49-61. to look like: <p class="cite">Alouf N., 1973. Biotope et description de <em>Niphargus altagahizi</em> n. sp., Amphipode Gammaridé souterrain du Liban, International Journal of Speleology 5: 49-61.</p> Any suggestions how to do this in OOoWriter macros perhaps, or any other application?

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• Properly removing an Integer from a List<Integer>

  - by Yuval A

  Here's a nice pitfall I just encountered. Consider a list of integers: List<Integer> list = new ArrayList<Integer>(); list.add(5); list.add(6); list.add(7); list.add(1); Any educated guess on what happens when you execute list.remove(1)? What about list.remove(new Integer(1))? This can cause some nasty bugs. What is the proper way to differentiate between remove(int index), which removes an element from given index and remove(Object o), which removes an element by reference, when dealing with lists of integers? The main point to consider here is the one @Nikita mentioned - exact parameter matching takes precedence over auto-boxing.

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• accessing required modules from other modules

  - by john smith

  I have a bare-bone express application, exactly the one that is created with the express command. I have installed socket.io and attached it to my server, like this: var app = express(), server = http.createServer(app), io = io.listen(server); server.listen(8000); Now, I also have the routes files, which is called like this: app.get('/', routes.index); Inside this module I have the following function: exports.index = function(req, res){ socket.emit('news', { message: "foo" }); }; This obviously leads to a 500 reference error, because the routes file is an exportable module, and obviously has no idea what the socket is, as it is located in the app.js file. Is there a way I can access this socket object from this, or any other file? Please note that it is attached to the express generated app. extra: what about getting/setting session data? Thanks in advance.

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• Django json serialization problem

  - by codingJoe

  I am having difficulty serializing a django object. The problem is that there are foreign keys. I want the serialization to have data from the referenced object, not just the index. For example, I would like the sponsor data field to say "sponsor.last_name, sponsor.first_name" rather than "13". How can I fix my serialization? json data: {"totalCount":"2","activities":[{"pk": 1, "model": "app.activity", "fields": {"activity_date": "2010-12-20", "description": "my activity", "sponsor": 13, "location": 1, .... model code: class Activity(models.Model): activity_date = models.DateField() description = models.CharField(max_length=200) sponsor = models.ForeignKey(Sponsor) location = models.ForeignKey(Location) class Sponsor(models.Model): last_name = models.CharField(max_length=20) first_name= models.CharField(max_length=20) specialty = models.CharField(max_length=100) class Location(models.Model): location_num = models.IntegerField(primary_key=True) location_name = models.CharField(max_length=100) def activityJSON(request): activities = Activity.objects.all() total = activities.count() activities_json = serializers.serialize("json", activities) data = "{\"totalCount\":\"%s\",\"activities\":%s}" % (total, activities_json) return HttpResponse(data, mimetype="application/json")

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• Retrieve names by ratio of their occurance

  - by jjiffer

  Hello, I'm somewhat new to SQL queries, and I'm struggling with this particular problem. Let's say I have query that returns the following 3 records (kept to one column for simplicity): Tom Jack Tom And I want to have those results grouped by the name and also include the fraction (ratio) of the occurrence of that name out of the total records returned. So, the desired result would be (as two columns): Tom | 2/3 Jack | 1/3 How would I go about it? Determining the numerator is pretty easy (I can just use COUNT() and GROUP BY name), but I'm having trouble translating that into a ratio out of the total rows returned. Any help is much appreciated!

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• ImportError and Django driving me crazy

  - by John Peebles

  OK, I have the following directory structure (it's a django project): - project -- app and within the app folder, there is a scraper.py file which needs to reference a class defined within models.py I'm trying to do the following: import urllib2 import os import sys import time import datetime import re import BeautifulSoup sys.path.append('/home/userspace/Development/') os.environ['DJANGO_SETTINGS_MODULE'] = 'project.settings' from project.app.models import ClassName and this code just isn't working. I get an error of: Traceback (most recent call last): File "scraper.py", line 14, in from project.app.models import ClassName ImportError: No module named project.app.models This code above used to work, but broke somewhere along the line and I'm extremely confused as to why I'm having problems. On SnowLeopard using python2.5.

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• Jquery and binding an event to an iframe

  - by dbr

  **I'm currently using a jquery textselect plugin to fire alerts based on the selection text anywhere on the page and it works just fine doing something like: $(document).ready(function() { $(document).bind('textselect', function(e) { alert(e.text); }); }); I've since had to add an iframe to the page and I need the text selection to work on text within the iframe as well. I'm trying to do something like this but it's not working: $(document).ready(function() { $('#iframeId').load(function() { $(document.getElementById("iframeId").contentWindow).bind('textselect',function(e) { alert(e.text); }); }); At this point I've tried a whole mess of ways to reference the iframe document without any success. Any ideas?**

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• MYSQL Inner Join two table over two keys

  - by bertsisterwanda

  I am doing a query to return all users shopping carts, stored in the sb_carts table. The product information stored in sb_carts is referenced over two keys product_sku and school_id. It needs to reference both to return a unique product with unique stock levels etc. When I execute the following query it returns one row, I am expecting 3 rows. I have tried breaking the inner join into two separate joins but this still returns only 1 result. joining only on one key has the desired result, but may be retuning the wrong product. A left join returns 3 rows but some data is missing product specific Here is a simplified example of what I am doing SELECT sb_carts.product_sku FROM sb_carts INNER JOIN sb_products ON sb_products.sku = sb_carts.product_sku AND sb_products.school_id = sb_carts.school_id WHERE sb_carts.order_id = 0 AND sb_carts.user_id = 2 GROUP BY sb_carts.cart_id

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• Using static mutex in a class

  - by Dmitry Yudakov

  I have a class that I can have many instances of. Inside it creates and initializes some members from a 3rd party library (that use some global variables) and is not thread-safe. I thought about using static boost::mutex, that would be locked in my class constructor and destructor. Thus creating and destroying instances among my threads would be safe for the 3rd party members. class MyClass { static boost::mutex mx; // 3rd party library members public: MyClass(); ~MyClass(); }; MyClass::MyClass() { boost::mutex::scoped_lock scoped_lock(mx); // create and init 3rd party library stuff } MyClass::~MyClass() { boost::mutex::scoped_lock scoped_lock(mx); // destroy 3rd party library stuff } I cannot link because I receive error: undefined reference to `MyClass::mx` Do I need some special initialization of such static member? Is the whole conception of static mutex wrong?

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• Left with extra UITableViewCell after re-ordering

  - by Mark F

  After going into Edit mode, moving a cell, and leaving edit mode, i am left with one extra cell sitting on top of its duplicate cell while still in edit mode. The problem has to be somewhere in here: - (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath { NSMutableArray *array = [[fetchedResultsController fetchedObjects] mutableCopy]; id objectToMove = [[array objectAtIndex:sourceIndexPath.row] retain]; [array removeObjectAtIndex:sourceIndexPath.row]; [array insertObject:objectToMove atIndex:destinationIndexPath.row]; [objectToMove release]; for (int i=0; i<[array count]; i++) { [(NSManagedObject *)[array objectAtIndex:i] setValue:[NSNumber numberWithInt:i] forKey:@"userOrder"]; } [array release]; } Any guidance greatly appreciated!

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• Orbital equations, and power required to run them

  - by Adam Davis

  Due to a discussion on the SO IRC today, I'm curious about orbital mechanics, and The equations needed to solve orbital problems The computing power required to solve complex problems The question in particular is calculating when the Earth will plow into the Sun (or vice versa, depending on the frame of reference). I suspect that all the gravitational pulls within our solar system may need to be calculated, which makes me wonder what type of computer cluster is required, or can this be done on a single box? I don't have the experience to do a back of the napkin test here, but perhaps you do? Also, much thx to Gortok for the original inspiration (see comments).

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• get the row number from table view

  - by Faizan Tanveer

  i am new in iphone development, i am using table view to list name of the student, what i want to do is i want to get the row number of the cell the user pressed , currently i can get the name(string) of the cell, //code in didSelectRowAtIndexPath //the obj.name where is a string, it works fine obj.name=[obj.studentname objectAtIndex:indexPath.row]; //if i try obj.num , where num is nsinteger .i am getting errors of type i dnt understand obj.num=[[obj.studentname objectAtIndex:indexPath.row]count]; i even tried but i cant get the number. example if faizan lies on 12th cell. what i want to do is,is save 12 in a number and show it on the next view label.i cant put it in the variable thanks for your help in advance

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• Android EditText within a ListView

  - by metalideath

  I have created a custom Array Adapter to bind a custom row that contains some static text and an editable EditText. I am trying to register to be notified when the user changes the text within the edit text and when notified to determine which ArrayList row the modified EditText corresponds to. In the past with other types of views such as a Spinner I could simply put a reference to the parent view and the row number into the tag for the Spinner view. And then when I was notified that the value changed I read the tag to determine how to correlate it back to the master ArrayList. The problem with registering to be notifed with an EditText change is that you do not get back a view but instead get a TextWatcher and I have no way to correlate back to the parent view or ArrayList row. What is the technique that you need to use in this circumstance?

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• IntPtr arithmetics

  - by Luca

  I tried to allocate an array of structs in this way: struct T { int a; int b; } data = Marshal.AllocHGlobal(count*Marshal.SizeOf(typeof(T)); ... I'd like to access to allocated data "binding" a struct to each element in array allocated with AllocHGlobal... something like this T v; v = (T)Marshal.PtrToStructure(data+1, typeof(T)); but i don't find any convenient way... why IntPtr lack of arithmetics? How can I workaround this is a "safe" way? Someone could confirm that PtrToStructure function copy data into the struct variable? In other words, modifing the struct reflect modifications in the structure array data, or not? Definitely, I want to operate on data pointed by an IntPtr using struct, without copying data each time, avoiding unsafe code. Thank all!

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• Counting down to zero in contrast to counting up to length - 1

  - by Helper Method

  Is it recommended to count in small loops (where possible) down from length - 1 to zero instead of counting up to length - 1? 1.) Counting down for (int i = a.length - 1; i >= 0; i--) { if (a[i] == key) return i; } 2.) Counting up for (int i = 0; i < a.length; i++) { if (a[i] == key) return i; } The first one is slightly faster that the second one (because comparing to zero is faster) but is a little more error-prone in my opinion. Besides, the first one could maybe not be optimized by future improvements of the JVM. Any ideas on that?

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• Can't get up with RIA demo: part 2

  - by Budda

  Here is a topic: http://stackoverflow.com/questions/2507734/cant-get-up-with-ria-demo where I've described problem with getting access to DomainContext object on the client. That time problem was resolved himself (without any actions from my side, with Visual Studio restart). At the moment, I had the same problem on another PC (Vista x64, VS2008, Silverlight 3.0, RIA Services Toolkit): ThomasDomainContext class that inherits DomainContext was not visible from the page's codebehind file. Again, it was resolved after VS restart and after that I got another problem: Error 1 'VfmElita.Web.ClientBin.ThomasDomainContext' does not contain a definition for 'employee' and no extension method 'employee' accepting a first argument of type 'VfmElita.Web.ClientBin.ThomasDomainContext' could be found (are you missing a using directive or an assembly reference?) D:\Project\Budda\VFMElita\VfmElitaSilverlightClient\MainPage.xaml.cs for the following lines of code (error is noticed for the 31st line): 30: var context = new ThomasDomainContext(); 31: grid1.ItemsSource = context.employee; 32: context.Load(context.GetEmployeeQuery()); Any help is welcome. P.S. Please note, that source code create on the 1st machine is successfully compilable and launchable

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• Why is floating point byte swapping different from integer byte swapping?

  - by CJ

  I have a binary file of doubles that I need to load using C++. However, my problem is that it was written in big-endian format but the fstream operator will then read the number wrong because my machine is little-endian. It seems like a simple problem to resolve for integers, but for doubles and floats the solutions I have found won't work. How can I (or should I) fix this? I read this as a reference for integer byte swapping: http://stackoverflow.com/questions/105252/how-do-i-convert-between-big-endian-and-little-endian-values-in-c

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• Filter zipcodes by proximity in Django with the Spherical Law of Cosines

  - by spiffytech

  I'm trying to handle proximity search for a basic store locater in Django. Rather than haul PostGIS around with my app just so I can use GeoDjango's distance filter, I'd like to use the Spherical Law of Cosines distance formula in a model query. I'd like all of the calculations to be done in the database in one query, for efficiency. An example MySQL query from The Internet implementing the Spherical Law of Cosines like this: SELECT id, ( 3959 * acos( cos( radians(37) ) * cos( radians( lat ) ) * cos( radians( lng ) - radians(-122) ) + sin( radians(37) ) * sin( radians( lat ) ) ) ) AS distance FROM stores HAVING distance < 25 ORDER BY distance LIMIT 0 , 20; The query needs to reference the Zipcode ForeignKey for each store's lat/lng values. How can I make all of this work in a Django model query?

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• Is this a valid jquery getJSON call?

  - by Pandiya Chendur

  I am using jquery getJSON with asp.net mvc controller... I cant able to get it work.... public JsonResult GetMaterials(int currentPage,int pageSize) { var materials = consRepository.FindAllMaterials().AsQueryable(); var results = new PagedList<MaterialsObj>(materials, currentPage-1, pageSize); return Json(results); } and i am calling this with, $.getJSON('Materials/GetMaterials', "{'currentPage':1,'pageSize':5}", function(data) { }); This call doesn't seem to work.... when inspected through firebug i found this, The parameters dictionary contains a null entry for parameter 'currentPage' of non-nullable type 'System.Int32' for method 'System.Web.Mvc.JsonResult GetMaterials(Int32, Int32)' in 'CrMVC.Controllers.MaterialsController'. To make a parameter optional its type should be either a reference type or a Nullable type.<br> Parameter name: parameters

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• LINQ-to-XML to DataGridView: Cannot edit fields -- How to fix?

  - by Pretzel

  I am currently doing LINQ-to-XML and populating a DataGridView with my query just fine. The trouble I am running into is that once loaded into the DataGridView, the values appear to be Un-editable (ReadOnly). Here's my code: var barcodes = (from src in xmldoc.Descendants("Container") where src.Descendants().Count() > 0 select new { Id = (string)src.Element("Id"), Barcode = (string)src.Element("Barcode"), Quantity = float.Parse((string)src.Element("Quantity").Attribute("value")) }).Distinct(); dataGridView1.DataSource = barcodes.ToList(); I read somewhere that the "DataGridView will be in ReadOnly mode when you use Anonymous types." But I couldn't find an explanation why or exactly what to do about it. Any ideas?

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• Possible Performance Considerations using Linq to SQL Repositories

  - by Robert Harvey

  I have an ASP.NET MVC application that uses Linq to SQL repositories for all interactions with the database. To deal with data security, I do trimming to filter data to only those items to which the user has access. This occurs in several places: Data in list views Links in a menu bar A treeview on the left hand side containing links to content Role-based security A special security attribute, inheriting from AuthorizeAttribute, that implements content-based authorization on every controller method. Each of these places instantiates a repository, which opens a Linq to Sql DataContext and accesses the database. So, by my count, each request for a page access opens at least six separate Linq to SQL DataContexts. Should I be concerned about this from a performance perspective, and if so, what can be done to mitigate it?

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• Exception Error in c#

  - by Kumu

  using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.IO; using System.Runtime.Serialization.Formatters.Binary; namespace FoolballLeague { public partial class MainMenu : Form { FootballLeagueDatabase footballLeagueDatabase; Game game; Login login; public MainMenu() { InitializeComponent(); changePanel(1); } public MainMenu(FootballLeagueDatabase footballLeagueDatabaseIn) { InitializeComponent(); footballLeagueDatabase = footballLeagueDatabaseIn; } private void Form_Loaded(object sender, EventArgs e) { } private void gameButton_Click(object sender, EventArgs e) { int option = 0; changePanel(option); } private void scoreboardButton_Click(object sender, EventArgs e) { int option = 1; changePanel(option); } private void changePanel(int optionIn) { gamePanel.Hide(); scoreboardPanel.Hide(); string title = "Football League System"; switch (optionIn) { case 0: gamePanel.Show(); this.Text = title + " - Game Menu"; break; case 1: scoreboardPanel.Show(); this.Text = title + " - Display Menu"; break; } } private void logoutButton_Click(object sender, EventArgs e) { login = new Login(); login.Show(); this.Hide(); } private void addGameButton_Click(object sender, EventArgs e) { if ((homeTeamTxt.Text.Length) == 0) MessageBox.Show("You must enter a Home Team"); else if (homeScoreUpDown.Value > 9 || homeScoreUpDown.Minimum < 0) MessageBox.Show("You must enter one digit between 0 and 9"); else if ((awayTeamTxt.Text.Length) == 0) MessageBox.Show("You must enter a Away Team"); else if (homeScoreUpDown.Value > 9 || homeScoreUpDown.Value < 0) MessageBox.Show("You must enter one digit between 0 to 9"); else { //checkGameInputFields(); game = new Game(homeTeamTxt.Text, int.Parse(homeScoreUpDown.Value.ToString()), awayTeamTxt.Text, int.Parse(awayScoreUpDown.Value.ToString())); MessageBox.Show("Home Team -" + '\t' + homeTeamTxt.Text + '\t' + "and" + '\r' + "Away Team -" + '\t' + awayTeamTxt.Text + '\t' + "created"); footballLeagueDatabase.AddGame(game); //clearCreateStudentInputFields(); } } private void timer1_Tick(object sender, EventArgs e) { displayDateAndTime(); } private void displayDateAndTime() { dateLabel.Text = DateTime.Today.ToLongDateString(); timeLabel.Text = DateTime.Now.ToShortTimeString(); } private void displayResultsButton_Click(object sender, EventArgs e) { Game game = new Game(homeTeamTxt.Text, int.Parse(homeScoreUpDown.Value.ToString()), awayTeamTxt.Text, int.Parse(awayScoreUpDown.Value.ToString())); gameResultsListView.Items.Clear(); gameResultsListView.View = View.Details; ListViewItem row = new ListViewItem(); row.SubItems.Add(game.HomeTeam.ToString()); row.SubItems.Add(game.HomeScore.ToString()); row.SubItems.Add(game.AwayTeam.ToString()); row.SubItems.Add(game.AwayScore.ToString()); gameResultsListView.Items.Add(row); } private void displayGamesButton_Click(object sender, EventArgs e) { Game game = new Game("Home", 2, "Away", 4);//homeTeamTxt.Text, int.Parse(homeScoreUpDown.Value.ToString()), awayTeamTxt.Text, int.Parse(awayScoreUpDown.Value.ToString())); modifyGamesListView.Items.Clear(); modifyGamesListView.View = View.Details; ListViewItem row = new ListViewItem(); row.SubItems.Add(game.HomeTeam.ToString()); row.SubItems.Add(game.HomeScore.ToString()); row.SubItems.Add(game.AwayTeam.ToString()); row.SubItems.Add(game.AwayScore.ToString()); modifyGamesListView.Items.Add(row); } } } This is the whole code and I got same error like previous question. Unhandled Exception has occurred in you application.If you click...............click Quit.the application will close immediately. Object reference not set to an instance of an object. And the following details are in the error message. ***** Exception Text ******* System.NullReferenceException: Object reference not set to an instance of an object. at FoolballLeague.MainMenu.addGameButton_Click(Object sender, EventArgs e) in C:\Users\achini\Desktop\FootballLeague\FootballLeague\MainMenu.cs:line 91 at System.Windows.Forms.Control.OnClick(EventArgs e) at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent) at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.ButtonBase.WndProc(Message& m) at System.Windows.Forms.Button.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) I need to add the games to using the addGameButton and the save those added games and display them in the list view (gameResultsListView). Now I can add a game and display in the list view.But when I pressed the button addGameButton I got the above error message. If you can please give me a solution to this problem.

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