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  • Question about C# 4.0's generics covariance

    - by devoured elysium
    Having defined this interface: public interface IInputBoxService<out T> { bool ShowDialog(); T Result { get; } } Why does the following code work: public class StringInputBoxService : IInputBoxService<string> { ... } ... IInputBoxService<object> service = new StringInputBoxService(); and this doesn't?: public class IntegerInputBoxService : IInputBoxService<int> { ... } ... IInputBoxService<object> service = new IntegerInputBoxService(); Does it have anything to do with int being a value type? If yes, how can I circumvent this situation? Thanks

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  • C# casting question: from IEnumerable to custom type

    - by Sarah Vessels
    I have a custom class called Rows that implements IEnumerable<Row>. I often use LINQ queries on Rows instances: Rows rows = new Rows { row1, row2, row3 }; IEnumerable<Row> particularRows = rows.Where<Row>(row => condition); What I would like is to be able to do the following: Rows rows = new Rows { row1, row2, row3 }; Rows particularRows = (Rows)rows.Where<Row>(row => condition); However, I get a "System.InvalidCastException: Unable to cast object of type 'WhereEnumerableIterator1[NS.Row]' to type 'NS.Rows'". I do have a Rows constructor taking IEnumerable<Row>, so I could do: Rows rows = new Rows { row1, row2, row3 }; Rows particularRows = new Rows(rows.Where<Row>(row => condition)); This seems bulky, however, and I would love to be able to cast an IEnumerable<Row> to be a Rows since Rows implements IEnumerable<Row>. Any ideas?

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  • JavaScript Regex question

    - by Vincent
    All, I have following function to check for invalid symbols entered in a text box and return true or false. How can I modify this function to also check for occurrences like http:// and https:// and ftp:// return false if encountered ? function checkURL(textboxval) { return ! (/[<>()#'"]|""/.test(textboxval)); } Thanks

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  • GdkEventKey. Key value question

    - by spajak
    Hi How to translate GdkEventKey.keyval with level 0 to key value with level == 0? For example: GDK_ISO_Left_Tab ==> GDK_Tab? Of course not using switch/case for every key. I need to get particular key, not a character.

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  • SQL aggregate query question

    - by Phil
    Hi, Can anyone help me with a SQL query in Apache Derby SQL to get a "simple" count. Given a table ABC that looks like this... id a b c 1 1 1 1 2 1 1 2 3 2 1 3 4 2 1 1 ** 5 2 1 2 ** ** 6 2 2 1 ** 7 3 1 2 8 3 1 3 9 3 1 1 How can I write a query to get a count of how may distinct values of 'a' have both (b=1 and c=2) AND (b=2 and c=1) to get the correct result of 1. (the two rows marked match the criteria and both have a value of a=2, there is only 1 distinct value of a in this table that match the criteria) The tricky bit is that (b=1 and c=2) AND (b=2 and c=1) are obviously mutually exclusive when applied to a single row. .. so how do I apply that expression across multiple rows of distinct values for a? These queries are wrong but to illustrate what I'm trying to do... "SELECT DISTINCT COUNT(a) WHERE b=1 AND c=2 AND b=2 AND c=1 ..." .. (0) no go as mutually exclusive "SELECT DISTINCT COUNT(a) WHERE b=1 AND c=2 OR b=2 AND c=1 ..." .. (3) gets me the wrong result. SELECT COUNT(a) (CASE WHEN b=1 AND c=10 THEN 1 END) FROM ABC WHERE b=2 AND c=1 .. (0) no go as mutually exclusive Cheers, Phil.

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  • css position question: layers with z-index?

    - by user239831
    hey guys, i have a probably rather simpel problem: my website has two layers: 1) a drag&drop navigation on top which should be positioned absolute, so scrolling doesn't affect the bars. 2) a content area in the back behind the navigation which should be scrollable. you can see what i mean right here: http://jsfiddle.net/Pghqv/ however now, i cannot click links in my content-area in the back. any ideas or solutions how i can still have the same position result and the links in the back are working? thank you very much.

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  • php mail send form question?

    - by eberswine
    Wondering if anyone know how to automatically send the user an email after he/she fills out a form. I have the form emailed to me after it gets submitted, but I can't figure out how to capture the user's email from the form field and have it send it to them automatically??? Here is some code that I use to send the mail: //mail the message before redirecting if($_POST['dosend'] == "yes"){ // The message $headers = "From: [email protected]"; $message = "NEW Message :: ".$_POST['event_name']." \n Email: ".$_POST['email']." \n Click link to http://www.domain.com/admin/ Approve this Event!"; // Send mail('[email protected]', 'New :: Calendar Message', $message, $headers); } //end mail

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  • C++ Newbie Question

    - by JavaMan
    I am from a Java background and is learning C++. I encountered the following C++ code: String source = String::New("'Hello' + ', World'"); As what I understand so far, this should be a call to static member function 'New' of class 'String'. But, I've searched through the whole header file defining 'String', there is not any static member named 'New' in the String class or its super classes. Is there any special meaning attached to String class or the New member function in C++?

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  • javacript question related to use of ' and "

    - by vatismarty
    my_window.document.write(' function redirect(linkid) { opener.location.href=linkid; window.close(); } Hello Thank you.If you accidentally closed our website click here to go back to our website '); This is my piece of code to close a already opened pop up window by redirecting it to google.com. I think there is some problem with matching the apostrophes ' and "... how to code with (' (" (' ') ") ')... is this correct... please help me with this.

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  • PHP syntax question: global $argv, $argc;

    - by Andrew
    So I have a PHPUnit test, and found this code within a function. global $argv, $argc; echo $argc; print_r($argv); I understand what these variables represent (arguments passed from the command line), but I've never seen this syntax before:global $argv, $argc; What specifically is going on here?

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  • Python client / server question

    - by AustinM
    I'm working on a bit of a project in python. I have a client and a server. The server listens for connections and once a connection is received it waits for input from the client. The idea is that the client can connect to the server and execute system commands such as ls and cat. This is my server code: import sys, os, socket host = '' port = 50105 s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.bind((host, port)) print("Server started on port: ", port) s.listen(5) print("Server listening\n") conn, addr = s.accept() print 'New connection from ', addr while (1): rc = conn.recv(5) pipe = os.popen(rc) rl = pipe.readlines() file = conn.makefile('w', 0) file.writelines(rl[:-1]) file.close() conn.close() And this is my client code: import sys, socket s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) host = 'localhost' port = input('Port: ') s.connect((host, port)) cmd = raw_input('$ ') s.send(cmd) file = s.makefile('r', 0) sys.stdout.writelines(file.readlines()) When I start the server I get the right output, saying the server is listening. But when I connect with my client and type a command the server exits with this error: Traceback (most recent call last): File "server.py", line 21, in <module> rc = conn.recv(2) File "/usr/lib/python2.6/socket.py", line 165, in _dummy raise error(EBADF, 'Bad file descriptor') socket.error: [Errno 9] Bad file descriptor On the client side, I get the output of ls but the server gets screwed up.

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  • Static method,new thread performance question

    - by ylazez
    Hey guys i just have two questions about two methods used in many controllers/servlets in my app: 1-what is the difference between calling a static method in a util class or a non static method (like methods dealing with dates i.e getting current time,converting between timezones), which is better ? 2-what is the difference between calling a method(contain too many logic like sending emails) in the controller directly or running this method in a different thread ?

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  • A question about matrix manipulation

    - by appi
    Given a 1*N matrix or an array, how do I find the first 4 elements which have the same value and then store the index for those elements? PS: I'm just curious. What if we want to find the first 4 elements whose value differences are within a certain range, say below 2? For example, M=[10,15,14.5,9,15.1,8.5,15.5,9.5], the elements I'm looking for will be 15,14.5,15.1,15.5 and the indices will be 2,3,5,7.

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  • managedObjectContext question...

    - by treasure
    Hello, I have an app which is a UITabBarController, I have defined two subviews Both tabs have their Class attribute in the Identity Inspector set to UINavigationController. Now i have managed to get this far with my coding after VERY LONG trials. - (void)viewDidLoad { [super viewDidLoad]; myAppDelegate *appDelegate = (myAppDelegate *)[[UIApplication sharedApplication] delegate]; self.managedObjectContext = appDelegate.managedObjectContext; { NSError *error = nil; NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; [fetchRequest setEntity:[NSEntityDescription entityForName:@"User" inManagedObjectContext:self.managedObjectContext]]; NSArray *fetchedItems = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error]; NSEntityDescription *entityDesc = [NSEntityDescription entityForName:@"User" inManagedObjectContext:self.managedObjectContext]; // replace the old data with new. this DOESNT WORK if (fetchedItems.count > 0) { Usr *newUsr; for (newUsr in fetchedItems) { if ([newUsr.name isEqualToString:@"Line One"]) { newUsr.uName = @"Line One (new)"; } } } //add a new default data. THIS ADDS DATA TO MY TABLEVIEW BUT IT DOESNT SAVE THEM TO THE SQLITE User *addedDefaultdata = nil; addedDefaultdata = [[User alloc] initWithEntity:entityDesc insertIntoManagedObjectContext:self.managedObjectContext]; addedDefaultdata.name = @"Added new 1"; [addedDefaultdata release]; } NSError *error = nil; if (![[self fetchedResultsController] performFetch:&error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } } and my appdelegate looks like this: - (void)applicationDidFinishLaunching:(UIApplication *)application { [application setStatusBarStyle:UIStatusBarStyleBlackOpaque]; [window addSubview:navigationController.view]; [window makeKeyAndVisible]; } now I cannot quire the "User" at all! although i get no errors or warnings! Any suggestions would be much appreciated! Thanks

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  • Hash Table question [closed]

    - by Fatimah
    I need your help to solve this program ... Implement a separate chaining hash table that stores strings. You’ll need a hash function that converts string into an index number. Assume the strings will be lowercase words, so 26 characters will suffice.

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  • OOP PHP simple question

    - by Tristan
    Hello, I'm new to OOP in PHP, is that to seems correct ? class whatever { Function Maths() { $this->sql->query($requete); $i = 0; while($val = mysql_fetch_array($this)) { $tab[i][average] = $val['average']; $tab[i][randomData] = $val['sum']; $i=$i+1; } return $tab; } I want to access the data contained in the array $foo = new whatever(); $foo->Maths(); for ($i, $i <= endOfTheArray; i++) { echo Maths->tab[i][average]; echo Maths->tab[i][randomData]; } Thank you ;)

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  • Inheritance question / problem

    - by Itsik
    I'm creating a custom Layout for android. The layout implementation is exactly the same, but once I need to extend from RelativeLayout, and once from LinearLayout. class Layout1 extends LinearLayout { // methods and fields } class Layout2 extends RelativeLayout { // the same EXACT methods and fields } How can I use inheritance to avoid DRY and implement my methods once.

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  • Question about architecting asp.net mvc application ?

    - by Misnomer
    I have read little bit about architecture and also patterns in order to follow the best practices. So this is the architecture we have and I wanted to know what you think of it and any proposed changes or improvements to it - Presentation Layer - Contains all the views,controllers and any helper classes that the view requires also it containes the reference to Model Layer and Business Layer. Business Project - Contains all the business logic and validation and security helper classes that are being used by it. It contains a reference to DataAccess Layer and Model Layer. Data Access Layer - Contains the actual queries being made on the entity classes(CRUD) operations on the entity classes. It contains reference to Model Layer. Model Layer - Contains the entity framework model,DTOs,Enums.Does not really have a reference to any of the above layers. What are your thoughts on the above architecture ? The problem is that I am getting confused by reading about like say the repository pattern, domain driven design and other design patterns. The architecture we have although not that strict still is relatively alright I think and does not really muddle things but I maybe wrong. I would appreciate any help or suggestions here. Thanks !

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  • Question on different ways to link tables

    - by dotnetdev
    What is the difference between linking two tables and then the PK is an FK in the other table, but the FK has not got the primary key option (so it does not have the gold key), and having the PK in one table as a PK in another table? Am I right to think that the second option is for a many-to-many relationship? Thanks

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