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  • Why do they initialize pointers this way?

    - by Rob
    In almost all of the books I read and examples I go through I see pointers initialized this way. Say that I have a class variable NSString *myString that I want to initialize. I will almost always see that done this way: -(id)init { if (self = [super init]) { NSString *tempString = [[NSString alloc] init]; myString = tempString; [tempString release]; } return self; } Why can't I just do the following? -(id)init { if (self = [super init]) { myString = [[NSString alloc] init]; } return self; } I don't see why the extra tempString is ever needed in the first place, but I could be missing something here with memory management. Is the way I want to do things acceptable or will it cause some kind of leak? I have read the Memory Management Guide on developer.apple.com and unless I am just missing something, I don't see the difference.

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  • Class design question (Disposable and singleton behavior)

    - by user137348
    The Repository class has singleton behavior and the _db implements the disposable pattern. As excepted the _db object gets disposed after the first call and because of the singleton behavior any other call of _db will crash. [ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)] public class Repository : IRepository { private readonly DataBase _db; public Repository(DataBase db) { _db = db; } public int GetCount() { using(_db) { return _db.Menus.Count(); } } public Item GetItem(int id) { using(_db) { return _db.Menus.FirstOrDefault(x=>x.Id == id); } } } My question is, is there any way to design this class to work properly without removing the singleton behavior? The Repositoryclass will be serving big amount of requests.

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  • for loop vs while loop

    - by Atul
    We can use for loop and while loop for same purpose. in what means they effect our code if I use for instead of while? same question arises between if-else and switch-case? how to decide what to use? for example which one you would prefer? This code: int main() { int n; cin>>n; for(int i=0;i<n;i++) { do_something(); } return 0; } Or this code: int main() { int n,i=0; cin>>n; while(i<n) { do_something(); i++; } return 0; } if using for or while loop does not effect the code by any means then may I know What was the need to make 2 solution for same problem?

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  • session set for some Actions in Zend framework

    - by user202127
    I'm working on a website , in CV part users have some articles that only logged in users can download them.I want to make changes to the log in Action or preDispatch() to set session for guess users to download the articles, can some one tell me how it can be or give me some reference links. here is my preDispatch(): public function preDispatch() { $userInfo=$this->_auth->getStorage()->read(); $identity= $this->_auth->getIdentity(); if(!$this->_auth->hasIdentity()) { return $this->_helper->redirector('login','login'); } if(!isset($userInfo["member_id"]) || strlen($userInfo["member_id"])==0) { return $this->_helper->redirector('forbidden','login'); } $this->_accessType=2; }

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  • CRUD operations; do you notify whether the insert,update etc. went well ?

    - by danielovich
    Hi guys. I have a simple question for you (i hope) :) I have pretty much always used void as a "return" type when doing CRUD operations on data. Eg. Consider this code: public void Insert(IAuctionItem item) { if (item == null) { AuctionLogger.LogException(new ArgumentNullException("item is null")); } _dataStore.DataContext.AuctionItems.InsertOnSubmit((AuctionItem)item); _dataStore.DataContext.SubmitChanges(); } and then considen this code: public bool Insert(IAuctionItem item) { if (item == null) { AuctionLogger.LogException(new ArgumentNullException("item is null")); } _dataStore.DataContext.AuctionItems.InsertOnSubmit((AuctionItem)item); _dataStore.DataContext.SubmitChanges(); return true; } It actually just comes down to whether you should notify that something was inserted (and went well) or not ?

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  • C++ Basic Class Layout

    - by Spencer
    Learning C++ and see the class laid out like this: class CRectangle { int x, y; public: void set_values (int,int); int area () {return (x*y);} }; void CRectangle::set_values (int a, int b) { x = a; y = b; } I know Java and methods(functions) in Java are written within the class. The class looks like a Java interface. I know I can write the class like this: class CRectangle { int x, y; public: void set_values (int a, int b) { x = a; y = b; }; int area () {return (x*y);} }; But is there a difference or standard?

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  • Using PHP interfaces in Codeigniter

    - by John Stewart
    I am trying to find out how can I used PHP interfaces in my MVC design. I want to make sure that the design enforces an interface so that any new module would follow that. For example: <?php interface BaseAPI { public function postMessage($msg); } class ServiceAPI implements BaseAPI { public function postMessage($msg) { return $msg; } } class Service_Two_API implements BaseAPI { public function postMessage($msg) { return "can't do this: ".$msg; } } ?> I want to do this in CI. Is it possible? how should I design it?

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  • controling a float value with javascript

    - by kawtousse
    Hi, to control my input type and verify that its value is pretty a float in my form i deal with it in javascript like that: function verifierNombre () { var champ=document.getElementById("nperformed"); var str = champ.value; if(str.value==' '){champ.focus();} if (isNaN(str)) { alert("Invalid Valid! the field must be a number"); champ.focus(); return false; } return true; } but it still false because it doesn't accept really floats. so when entering a value like '11,2' the alert is declenched. I want to know how can I control float values with javascript. thanks.

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  • expecte ')' before className

    - by Akbarbuneri
    Hi I have a class DataObject as Header ::: #import <Foundation/Foundation.h> @interface DataObject : NSObject { NSString *erorrMessage; BOOL hasError; NSDictionary *dataValues; } @property(nonatomic, retain)NSString *erorrMessage; @property(nonatomic)BOOL hasError; @property(nonatomic, retain)NSDictionary *dataValues; @end Class Implementation:::: #import "DataObject.h" @implementation DataObject @synthesize erorrMessage; @synthesize hasError; @synthesize dataValues; @end And I have another class as DataManager Header as :::: #import <Foundation/Foundation.h> @interface DataManager : NSObject - (DataObject *)getData :(NSString*)url; @end Implementation :::: #import "DataManager.h" #import "DataObject.h" #import "JSON.h" @implementation DataManager - (DataObject *)getData :(NSString*)url{ DataObject* dataObject = [[DataObject alloc]init]; NSString *urlString = [NSString stringWithFormat:url]; NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:urlString]]; //TODO: Here we have to check the internet connection before requesting. NSError * erorrOnRequesting; NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:&erorrOnRequesting]; NSString* responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]; if( erorrOnRequesting != nil) { dataObject.hasError = YES; dataObject.erorrMessage = @"Error on requsting to the web server"; return dataObject; } NSError *errorOnParsing; SBJSON *json = [[SBJSON new] autorelease]; NSDictionary *dataValues = [json objectWithString:responseString error:&errorOnParsing]; [responseString release]; if(errorOnParsing != nil) { //TODO: We have to send the website a feedback that there is some problem on the server end. dataObject.hasError = YES; dataObject.erorrMessage = @"Error on parsing, the server returned invalid data."; return dataObject; } dataObject.hasError = NO; dataObject.dataValues = dataValues; return dataObject; } @end Now when I build I got an error in the DataManager header where I #import Dataobject header, it says "error: expected')' before DataObject" I don;t understand what I miss. Thanks for the help..

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  • How to compare two lists with duplicated items in one list?

    - by eladc
    I need to compare list_a against many others. my problem starts when there's a duplicated item in the other lists (two k's in other_b). my goal is to filter out all the lists with the same items (up to three matching items). list_a = ['j','k','a','7'] other_b = ['k', 'j', 'k', 'q'] other_c = ['k','k','9','k'] >>>filter(lambda x: not x in list_a,other_b) ['q'] I need a way that would return ['k', 'q'], because 'k' appears only once in list_a. comparing list_a and other_c with set() isn't good for my purpose since it will return only one element: k. while I need ['k','9','k'] I hope I was clear enough. Thank you

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  • Generate a valid array key from an URL string in PHP

    - by John Riche
    I have a PHP array with some predefined values: $aArray = array( 0 => 'value0', 1 => 'value1' ); I need to create a function where the string input will always return the same, valid, array key so that when I call: GiveMeAKey('http://www.google.com'); // May return 0 or 1 I receive always the same key (I don't care which one) from the array. Obvisously I can't store the relationship in a database and the string passed to the GiveMeAKey method can be any URL. I wonder if there is a way of doing that ?

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  • Mistake in display and insert methods (double-ended queue)

    - by MANAL
    1) My problem when i make remove from right or left program will be remove true but when i call diplay method the content wrong like this I insert 12 43 65 23 and when make remove from left program will remove 12 but when call display method show like this 12 43 65 and when make remove from right program will remove 23 but when call display method show like this 12 43 Why ?????? ); and when i try to make insert after remove write this Can not insert right because the queue is full . first remove right and then u can insert right where is the problem ?? Please Help me please 2) My code FIRST CLASS class dqueue { private int fullsize; //number of all cells private int item_num; // number of busy cells only private int front,rear; public int j; private double [] dqarr; //========================================== public dqueue(int s) //constructor { fullsize = s; front = 0; rear = -1; item_num = 0; dqarr = new double[fullsize]; } //========================================== public void insert(double data) { if (rear == fullsize-1) rear = -1; rear++; dqarr[rear] = data; item_num++; } public double removeLeft() // take item from front of queue { double temp = dqarr[front++]; // get value and incr front if(front == fullsize) front = 0; item_num --; // one less item return temp; } public double removeRight() // take item from rear of queue { double temp = dqarr[rear--]; // get value and decr rear if(rear == -1) // rear = item_num -1; item_num --; // one less item return temp; } //========================================= public void display () //display items { for (int j=0;j<item_num;j++) // for every element System.out.print(dqarr[j] +" " ); // display it System.out.println(""); } //========================================= public int size() //number of items in queue { return item_num; } //========================================== public boolean isEmpty() // true if queue is empty { return (item_num ==0); } } SECOND CLASS import java.util.Scanner; class dqueuetest { public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.println(" ***** Welcome here***** "); System.out.println(" ***** Mind Of Programming Group***** "); System.out.println(" _____________________________________________ "); System.out.println("enter size of your dqueue"); int size = input.nextInt(); dqueue mydq = new dqueue(size); System.out.println(""); System.out.println("enter your itemes"); //===================================== for(int i = 0;i<=size-1;i++) { System.out.printf("item %d:",i+1); double item = input.nextDouble(); mydq.insert(item); System.out.println(""); } //===================================== int queue =size ; int c = 0 ; while (c != 6) { System.out.println(""); System.out.println("************************************************"); System.out.println(" MAIN MENUE"); System.out.println("1- INSERT RIGHT "); System.out.println("2- REMOVE LEFT"); System.out.println("3- REMOVE RIGHT"); System.out.println("4- DISPLAY"); System.out.println("5- SIZE"); System.out.println("6- EXIT"); System.out.println("************************************************"); System.out.println("choose your operation by number(1-6)"); c = input.nextInt(); switch (c) { case 1: if (queue == size) System.out.print("Can not insert right because the queue is full . first remove right and then u can insert right "); else { System.out.print("enter your item: "); double item = input.nextDouble(); mydq.insert(item);} break; case 2: System.out.println("REMOVE FROM REAR :"); if( !mydq.isEmpty() ) { double item = mydq.removeLeft(); System.out.print(item + "\t"); } // end while System.out.println(""); mydq.display(); break; case 3: System.out.println("REMOVE FROM FRONT :"); if( !mydq.isEmpty() ) { double item = mydq.removeRight(); System.out.print(item + "\t"); } // end while System.out.println(""); mydq.display(); break; case 4: System.out.println("The items in Queue are :"); mydq.display(); break; case 5: System.out.println("The Size of the Queue is :"+mydq.size()); break; case 6: System.out.println("Good Bye"); break; default: System.out.println("wrong chiose enter again"); } //end switch } //end while } // end main }//end class

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  • Using varible in re.match in python

    - by screwuphead
    I am trying to create an array of things to match in a description line. So I cant ignore them later on in my script. Below is a sample script that I have been working on, on the side. Basically I am trying to take a bunch of strings and match it against a bunch of other strings. AKA: asdf or asfs or wrtw in string = true continue with script if not print this. import re ignorelist = ['^test', '(.*)set'] def guess(a): for ignore in ignorelist: if re.match(ignore, a): return('LOSE!') else: return('WIN!') a = raw_input('Take a guess: ') print guess(a) Thanks

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  • Performance implications of using a variable versus a magic number

    - by Nathan
    I'm often confused by this. I've always been taught to name numbers I use often using variables or constants, but if it reduces the efficiency of the program, should I still do it? Heres an example: private int CenterText(Font font, PrintPageEventArgs e, string text) { int recieptCenter = 125; int stringLength = Convert.ToInt32(e.Graphics.MeasureString(text, font)); return recieptCenter - stringLength / 2; } The above code is using named variables, but runs slower then this code: private int CenterText(Font font, PrintPageEventArgs e, string text) { return 125 - Convert.ToInt32(e.Graphics.MeasureString(text, font) / 2); } In this example, the difference in execution time is minimal, but what about in larger blocks of code?

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  • how to avoid repeating code?

    - by helloWorld
    I have some technical question, I have repeating code in my work, and I want to get rid of it, so I know that in C++ it is not good idea to use macro, but instead I must use inline function, is it good idea to use this function as inline: list<Data>::iterator foo(int data){ if(dataExists(data)){ list<Data>::iterator i; for(i = Data.begin(); i != Data.end(); ++i){ if(i->getData() == data){ break; } return i; //here I have one more problem, what can I return if data doesn't exist? } I'm beginner, and I think that this function is very unsafe, can somebody please give me advice, how can I improve my code, thanks in advance P.S. what usually do You use to avoid repeating code?

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  • error C2059: syntax error : ']', i cant figure out why this coming up in c++

    - by user320950
    void display_totals(); int exam1[100][3];// array that can hold 100 numbers for 1st column int exam2[100][3];// array that can hold 100 numbers for 2nd column int exam3[100][3];// array that can hold 100 numbers for 3rd column int main() { int go,go2,go3; go=read_file_in_array; go2= calculate_total(exam1[],exam2[],exam3[]); go3=display_totals; cout << go,go2,go3; return 0; } void display_totals() { int grade_total; grade_total=calculate_total(exam1[],exam2[],exam3[]); } int calculate_total(int exam1[],int exam2[],int exam3[]) { int calc_tot,above90=0, above80=0, above70=0, above60=0,i,j; calc_tot=read_file_in_array(exam[100][3]); exam1[][]=exam[100][3]; exam2[][]=exam[100][3]; exam3[][]=exam[100][3]; for(i=0;i<100;i++); { if(exam1[i] <=90 && exam1[i] >=100) { above90++; cout << above90; } } return exam1[i],exam2[i],exam3[i]; } int read_file_in_array(int exam[100][3]) { ifstream infile; int num, i=0,j=0; infile.open("grades.txt");// file containing numbers in 3 columns if(infile.fail()) // checks to see if file opended { cout << "error" << endl; } while(!infile.eof()) // reads file to end of line { for(i=0;i<100;i++); // array numbers less than 100 { for(j=0;j<3;j++); // while reading get 1st array or element infile >> exam[i][j]; cout << exam[i][j] << endl; } } infile.close(); return exam[i][j]; }

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  • Converting java language output to Joomla language output

    - by jax
    in java if I run : Locale.getDefault().toString() I get zh_tw I am sending this to a joomla site and setting the language like this: $lang = &JFactory::getLanguage(); $lang->setLanguage( $_GET['lang'] ); $lang->load(); however the site requires the following format zh-TW It appears that if it is not in that exact format the language will not change. Is there a function somewhere in java or php that will convert the format for me? I realise that I could write the method myself like this: public static String convertLanguageToJoomlaFormat(String lang) { String[] parts = lang.split("_"); if(parts.length ==2) return parts[0]+"-"+parts[1].toUpperCase(); return lang; } but am unsure if there are any cases where the format changes for particular languages.

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  • How do I search for values in a dictionary

    - by fishhead
    what would be the best way to search for a value in a dictionary. for instance I would like to search for modified objects, would going through the entire collection be the only way to do this? c#, .net 2.0 class RecA { public bool modified {get;set:} public string{get;set;} } class RecA_Dic : Dictionary<int,Rec_A> { public bool GetItemByKey(int key,out obj) { return this.TryGetValue(key, out obj); } public List<Rec_A> getModifiedItems() { List<Rec_A> li = new List<Rec_A>(); for(int i=0;i<this.count;i++) if (((Rec_A)this[i]).modified == true) li.Add((Rec_A)this[i]); return li; } }

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  • [super init] and loading NIB / XIB files?

    - by fuzzygoat
    I am a little curious, I have a view controller class and an NIB/XIB (both are named "MapViewController") If I do the following it loads the NIB with the matching name. -(id)init { self = [super initWithNibName:@"MapViewController" bundle:nil]; if(self) { do things ... } return self; } if on the other hand I just specify [super init] does Xcode just look for a NIB that matches the name of the controller, is that how this is working? -(id)init { self = [super init]; if(self) { do things ... } return self; } cheers Gary.

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  • c++ program debugged well with Cygwin4 (under Netbeans 7.2) but not with MinGW (under QT 4.8.1)

    - by GoldenAxe
    I have a c++ program which take a map text file and output it to a graph data structure I have made, I am using QT as I needed cross-platform program and GUI as well as visual representation of the map. I have several maps in different sizes (8x8 to 4096x4096). I am using unordered_map with a vector as key and vertex as value, I'm sending hash(1) and equal functions which I wrote to the unordered_map in creation. Under QT I am debugging my program with QT 4.8.1 for desktop MinGW (QT SDK), the program works and debug well until I try the largest map of 4096x4096, then the program stuck with the following error: "the inferior stopped because it received a signal from operating system", when debugging, the program halt at the hash function which used inside the unordered_map and not as part of the insertion state, but at a getter(2). Under Netbeans IDE 7.2 and Cygwin4 all works fine (debug and run). some code info: typedef std::vector<double> coordinate; typedef std::unordered_map<coordinate const*, Vertex<Element>*, container_hash, container_equal> vertexsContainer; vertexsContainer *m_vertexes (1) hash function: struct container_hash { size_t operator()(coordinate const *cord) const { size_t sum = 0; std::ostringstream ss; for ( auto it = cord->begin() ; it != cord->end() ; ++it ) { ss << *it; } sum = std::hash<std::string>()(ss.str()); return sum; } }; (2) the getter: template <class Element> Vertex<Element> *Graph<Element>::getVertex(const coordinate &cord) { try { Vertex<Element> *v = m_vertexes->at(&cord); return v; } catch (std::exception& e) { return NULL; } } I was thinking maybe it was some memory issue at the beginning, so before I was thinking of trying Netbeans I checked it with QT on my friend pc with a 16GB RAM and got the same error. Thanks.

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  • How can I map a String to a function in Java?

    - by Bears will eat you
    Currently, I have a bunch of Java classes that implement a Processor interface, meaning they all have a processRequest(String key) method. The idea is that each class has a few (say, <10) member Strings, and each of those maps to a method in that class via the processRequest method, like so: class FooProcessor implements Processor { String key1 = "abc"; String key2 = "def"; String key3 = "ghi"; // and so on... String processRequest(String key) { String toReturn = null; if (key1.equals(key)) toReturn = method1(); else if (key2.equals(key)) toReturn = method2(); else if (key3.equals(key)) toReturn = method3(); // and so on... return toReturn; } String method1() { // do stuff } String method2() { // do other stuff } String method3() { // do other other stuff } // and so on... } You get the idea. This was working fine for me, but now I need a runtime-accessible mapping from key to function; not every function actually returns a String (some return void) and I need to dynamically access the return type (using reflection) of each function in each class that there's a key for. I already have a manager that knows about all the keys, but not the mapping from key to function. My first instinct was to replace this mapping using if-else statements with a Map<String, Function>, like I could do in Javascript. But, Java doesn't support first-class functions so I'm out of luck there. I could probably dig up a third-party library that lets me work with first-class functions, but I haven't seen any yet, and I doubt that I need an entire new library. I also thought of putting these String keys into an array and using reflection to invoke the methods by name, but I see two downsides to this method: My keys would have to be named the same as the method - or be named in a particular, consistent way so that it's easy to map them to the method name. This seems WAY slower than the if-else statements I have right now. Efficiency is something of a concern because these methods will tend to get called pretty frequently, and I want to minimize unnecessary overhead. TL; DR: I'm looking for a clean, minimal-overhead way to map a String to some sort of a Function object that I can invoke and call (something like) getReturnType() on. I don't especially mind using a 3rd-party library if it really fits my needs. I also don't mind using reflection, though I would strongly prefer to avoid using reflection every single time I do a method lookup - maybe using some caching strategy that combines the Map with reflection. Thoughts on a good way to get what I want? Cheers!

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  • How do I guarantee row uniqueness in MySQL without the use of a UNIQUE constraint?

    - by MalcomTucker
    Hi I have some fairly simple requirements but I'm not sure how I implement them: I have multiple concurrent threads running the same query The query supplies a 'string' value - if it exists in the table, the query should return the id of the matching row, if not the query should insert the 'string' value and return the last inserted id The 'string' column is (and must be) a text column (it's bigger than varchar 255) so I cannot set it as unique - uniqueness must be enforced through the access mechanism The query needs to be in stored procedure format (which doesnt support table locks in MySQL) How can I guarantee that 'string' is unique? How can I prevent other threads writing to the table after another thread has read it and found no matching 'string' item? Thanks for any advice..

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  • how to make the two class fields(not referring any other table) as composite key in hibernate?

    - by M Sach
    i want to make pgId and pgName both as composite key where both pgId anf pgName are assgined values. i am not sure how should i go about it? on net i get examples where composite key column refering to column of some other table but not this kind of scenario? @Entity @Table(name = "PersonDetails") public class PersonDetailsData implements Serializable { private static final long serialVersionUID = 1L; @Id @Basic private int pgId; @Basic(optional = true) @Column(nullable = true) private int orgId; @Basic(optional = true) @Column(nullable = true) private String pgName; public PersonWikiDetailsData() { } public int getPpId() { return ppId; } public void setPpId(int ppId) { this.ppId = ppId; } public String getSpaceName() { return spaceName; } public void setSpaceName(String spaceName) { this.spaceName = spaceName; } }

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  • linq to sql update data

    - by pranay
    can i update my employee record as given in below function or i have to make query of employee collection first and than i update data public int updateEmployee(App3_EMPLOYEE employee) { DBContextDataContext db = new DBContextDataContext(); db.App3_EMPLOYEEs.Attach(employee); db.SubmitChanges(); return employee.PKEY; } or i have to do this public int updateEmployee(App3_EMPLOYEE employee) { DBContextDataContext db = new DBContextDataContext(); App3_EMPLOYEE emp = db.App3_EMPLOYEEs.Single(e => e.PKEY == employee.PKEY); db.App3_EMPLOYEEs.Attach(employee,emp); db.SubmitChanges(); return employee.PKEY; } But i dont want to use second option is there any efficient way to update data

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  • ASP.Net layered communication

    - by Chris Klepeis
    Hi, We're developing a layered web application. The specs: 3 layers, data layer, business layer, ui layer. Programmed in C# Data Layer uses the entity framework Currently we plan on having the data layer return IEnumerable<T> to the business layer via linq 2 entities, and the business layer will return data to the ui layer. Since the ui layer has no knowledge of the existance of the data layer, how would it handle a result of IEnumerable passed to it from the BLL, where T is defined in the data layer? Are there any GOOD example out there on how to do this. Please note that I'm extremely new to factories / interfaces / abstraction to loosely couple layers. I saw the question here http://stackoverflow.com/questions/917457/passing-data-in-an-ntier-application and it was recommended to have the entity layer shared amongst all layers... however I do not want the other layers to be able to query the database.

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