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  • Memory fragmentation @ boost::asio ?

    - by Poni
    I'm pretty much stuck with a question I never got an answer for, a question which addresses an extremely important issue; memory fragmentation at boost::asio. Found nothing at the documentation nor here at SO. The functions at boost::asio, for example async_write() & async_read_some() always allocate something. (in my case it's 144 & 96 bytes respectively, in VC9 Debug build). How do I know about it? I connect a client to the "echo server" example provided with this library. I put a breakpoint at "new.cpp" at the code of "operator new(size_t size)". Then I send "123". Breakpoint is hit! Now using the stack trace I can clearly see that the root to the "new" call is coming from the async_write() & async_read_some() calls I make in the function handlers. So memory fragmentation will come sooner or later, thus I can't use ASIO, and I wish I could! Any idea? Any helpful code example?

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  • What is the n in O(n) when comparing sorting algorithms?

    - by Mumfi
    The question is rather simple, but I just can't find a good enough answer. I've taken a look at the most upvoted question regarding the Big-Oh notation, namely this: Plain English explanation of Big O It says there that: For example, sorting algorithms are typically compared based on comparison operations (comparing two nodes to determine their relative ordering). Now let's consider the simple bubble sort algorithm: for (int i = arr.length - 1; i > 0 ; i--) { for (int j = 0; j<i; j++) { if (arr[j] > arr[j+1]) { switchPlaces(...) } } } I know that worst case is O(n^2) and best case is O(n), but what is n exactly? If we attempt to sort an already sorted algorithm (best case), we would end up doing nothing, so why is it still O(n)? We are looping through 2 for-loops still, so if anything it should be O(n^2). n can't be the number of comparison operations, because we still compare all the elements, right? This confuses me, and I appreciate if someone could help me.

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  • fluent nhibernate - storing and retrieving three classes in/from one table

    - by Will I Am
    Noob question. I have this situation where I have these objects: class Address { string Street; string City; ... } class User { string UserID; Address BillingAddress; Address MailingAddress; ... } What is the proper way of storing this data using (fluent) nHibernate? I could use a separate Address table and create a reference, but they are 1:1 relationships so I don't really want to incur the overhead of a join. Ideally I would store this as a single flat record. So, my question is, what is the proper way of storing an instance of class 'User' in such a way that it stores its contents and also the two addresses as a single record? My knowledge is failing me on how I can store this information in such a way that the two Address records get different column names (e.g. BillingAddress_Street and MailingAddress_Street, for example), and also how to read a record back into a User instance.

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  • POSIX Sockets: How to detect Ctrl-C sent over Telnet?

    - by ogott
    Short Question What's the right way to handle a Ctrl-C event sent over Telnet on the server side? Long Question After calling recv() on a socket, I'd like to handle some situations appropriately. One of them is to return a certain error code when Ctrl-C was received. What's the correct way to detect this? The following works, but it just doesn't seem right: size_t recv_count; static char ctrl_c[5] = {0xff, 0xf4, 0xff, 0xfd, 0x06}; recv_count = recv(socket, buffer, buffer_size, 0); if (recv_count == sizeof(ctrl_c) && memcmp(buffer, ctrl_c, sizeof(ctrl_c) == 0) { return CTRL_C_RECEIVED; } I found a comment on Ctrl-C in a side-note in this UNIX Socket FAQ: [...] (by the way, out-of-band is often used for that ctrl-C, too). As I understand, receiving out-of-band data is done using recv() with a certain flag as the last parameter. But when I'm waiting for data using recv() as I do in the code above, I can't read out-of-band data at the same time. Apart from that, I'm getting something using recv() without that oob-flag.

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  • Trying to create a group of button sprites

    - by user1449653
    Good day, I have like 15 images I need to be buttons. I have buttons working with a Box() (Box - looks like this) class Box(pygame.sprite.Sprite): def __init__(self): pygame.sprite.Sprite.__init__(self) self.image = pygame.Surface((35, 30)) self.image = self.image.convert() self.image.fill((255, 0, 0)) self.rect = self.image.get_rect() self.rect.centerx = 25 self.rect.centery = 505 self.dx = 10 self.dy = 10 I am trying to make the buttons work with image sprites. So I attempted to copy the class style of the box and do the same for my Icons.. code looks like this... class Icons(pygame.sprite.Sprite): def __init__(self): pygame.sprite.Sprite.__init__(self) self.image = pygame.image.load("images/airbrushIC.gif").convert() self.rect = self.image.get_rect() self.rect.x = 25 self.rect.y = 550 the code in the main() rect = image.get_rect() rect.x = 25 rect.y = 550 ic1 = Icons((screen.get_rect().x, screen.get_rect().y)) screen.blit(ic1.image, ic1.rect) pygame.display.update() This code produces a positional (accepts 1 argument but 2 are there) error or an image is not referenced error (inside the Icon class). I'm unsure if this is the right way to go about this anyways.. I know for sure that I need to load all the images (as sprites)... store them in an array... and then have my mouse check if it is clicking one of the items in the array using a for loop. Thanks. EDIT QUESTION 2: class Icons(pygame.sprite.Sprite): def init(self, *args): pygame.sprite.Sprite.init(self, *args) self.image = pygame.image.load("images/airbrushIC.gif").convert() self.rect = self.image.get_rect() ic1 = self.image self.rect.x = 10 self.rect.y = 490 self.image = pygame.image.load("images/fillIC.gif").convert() self.rect = self.image.get_rect() ic2 = self.image self.rect.x = 10 self.rect.y = 540 Thanks to your help I got the Icons class loading ONE image. Its not loading both. Obviously because its being overwritten by the second one. It seems that "class" for this purpose isn't what I need. Which begs the question how I make sprites outside of a class.. If there is a way to make the class work please let me know.

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  • Managing My Database in Source Control

    - by Jason
    As I am working with a new database project (within VS2008), and as I have never developed a database from scratch, I immediately began looking into how to manage a database within source control (in this case, Subversion). I found some information on SO, including this post: Keeping development databases in multiple environments in sync. One of the answers in particular pointed to a number of a links, all of which had good, useful information. I was reading a series of posts by K. Scott Allen which describe how he manages database change. From my reading (and please pardon the noobishness of my question), it seems as though the database itself is never checked into a repository. Rather, scripts that can build the database, along with test data (which is also populated from scripts) is checked into the repository. Ultimately, this means that, when a developer is testing his or her app, these scripts, which are part of the build process, are run. This ensures that the database is up-to-date, but is also run locally from every developer's machine. This makes sense to me (if I am indeed reading that correctly). However, if I am missing something, I would appreciate correction or additional guidance. In addition, another question I wanted to ask - does this also mean that I should NOT check in the mdf or ldf files that are created from Visual Studio? Thanks for any help and additional insight. Always appreciated.

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  • The best way to return related data in a SQL statement

    - by Darvis Lombardo
    I have a question on the best method to get back to a piece of data that is in a related table on the other side of a many-to-many relationship table. My first method uses joins to get back to the data, but because there are multiple matching rows in the relationship table, I had to use a TOP 1 to get a single row result. My second method uses a subquery to get the data but this just doesn't feel right. So, my question is, which is the preferred method, or is there a better method? The script needed to create the test tables, insert data, and run the two queries is below. Thanks for your advice! Darvis -------------------------------------------------------------------------------------------- -- Create Tables -------------------------------------------------------------------------------------------- DECLARE @TableA TABLE ( [A_ID] [int] IDENTITY(1,1) NOT NULL, [Description] [varchar](50) NULL) DECLARE @TableB TABLE ( [B_ID] [int] IDENTITY(1,1) NOT NULL, [A_ID] [int] NOT NULL, [Description] [varchar](50) NOT NULL) DECLARE @TableC TABLE ( [C_ID] [int] IDENTITY(1,1) NOT NULL, [Description] [varchar](50) NOT NULL) DECLARE @TableB_C TABLE ( [B_ID] [int] NOT NULL, [C_ID] [int] NOT NULL) -------------------------------------------------------------------------------------------- -- Insert Test Data -------------------------------------------------------------------------------------------- INSERT INTO @TableA VALUES('A-One') INSERT INTO @TableA VALUES('A-Two') INSERT INTO @TableA VALUES('A-Three') INSERT INTO @TableB (A_ID, Description) VALUES(1,'B-One') INSERT INTO @TableB (A_ID, Description) VALUES(1,'B-Two') INSERT INTO @TableB (A_ID, Description) VALUES(1,'B-Three') INSERT INTO @TableB (A_ID, Description) VALUES(2,'B-Four') INSERT INTO @TableB (A_ID, Description) VALUES(2,'B-Five') INSERT INTO @TableB (A_ID, Description) VALUES(3,'B-Six') INSERT INTO @TableC VALUES('C-One') INSERT INTO @TableC VALUES('C-Two') INSERT INTO @TableC VALUES('C-Three') INSERT INTO @TableB_C (B_ID, C_ID) VALUES(1, 1) INSERT INTO @TableB_C (B_ID, C_ID) VALUES(2, 1) INSERT INTO @TableB_C (B_ID, C_ID) VALUES(3, 1) -------------------------------------------------------------------------------------------- -- Get result - method 1 -------------------------------------------------------------------------------------------- SELECT TOP 1 C.*, A.Description FROM @TableC C JOIN @TableB_C BC ON BC.C_ID = C.C_ID JOIN @TableB B ON B.B_ID = BC.B_ID JOIN @TableA A ON B.A_ID = A.A_ID WHERE C.C_ID = 1 -------------------------------------------------------------------------------------------- -- Get result - method 2 -------------------------------------------------------------------------------------------- SELECT C.*, (SELECT A.Description FROM @TableA A WHERE EXISTS (SELECT * FROM @TableB_C BC JOIN @TableB B ON B.B_ID = BC.B_ID WHERE BC.C_ID = C.C_ID AND B.A_ID = A.A_ID)) FROM @TableC C WHERE C.C_ID = 1

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  • R from java with no graphics: is it worth moving to JRI

    - by LH
    I have a system set up that's been happily running R from a java servlet, spawning processed & hooking into the process's stdin, stdout, and stderr streams, as in the second andwer to this question. After a system upgrade (that included glibc), the input is no longer reaching the R process.* Until now, 'R --vanilla --slave -f [file] ...' was working fine for me. I also have no swing dependencies right now, so I'm somewhat reluctant to add them. (I may actually not be able to add swing dependencies; am I right that using REngine automatically brings swing in? The examples import all of swing.) Are there advantages to switching to JRI? What changes would I need to make to my R script? (It currently reads from stdin and writes to stdout). I'm not finding the provided examples terribly helpful for how to use JRI in this situation. Thanks for your help & comments. *I can't even tell if the problem is data being written too soon or too late, but that's a separate issue/question; if I move to JRI I'm hoping it all becomes moot.

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  • How to store arbitrary data for some HTML tags

    - by nickf
    I'm making a page which has some interaction provided by javascript. Just as an example: links which send an AJAX request to get the content of articles and then display that data in a div. Obviously in this example, I need each link to store an extra bit of information: the id of the article. The way I've been handling it in case was to put that information in the href link this: <a class="article" href="#5"> I then use jQuery to find the a.article elements and attach the appropriate event handler. (don't get too hung up on the usability or semantics here, it's just an example) Anyway, this method works, but it smells a bit, and isn't extensible at all (what happens if the click function has more than one parameter? what if some of those parameters are optional?) The immediately obvious answer was to use attributes on the element. I mean, that's what they're for, right? (Kind of). <a articleid="5" href="link/for/non-js-users.html"> In my recent question I asked if this method was valid, and it turns out that short of defining my own DTD (I don't), then no, it's not valid or reliable. A common response was to put the data into the class attribute (though that might have been because of my poorly-chosen example), but to me, this smells even more. Yes it's technically valid, but it's not a great solution. Another method I'd used in the past was to actually generate some JS and insert it into the page in a <script> tag, creating a struct which would associate with the object. var myData = { link0 : { articleId : 5, target : '#showMessage' // etc... }, link1 : { articleId : 13 } }; <a href="..." id="link0"> But this can be a real pain in butt to maintain and is generally just very messy. So, to get to the question, how do you store arbitrary pieces of information for HTML tags?

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  • Applying iterative algorithm to a set of rows from database

    - by Corvin
    Hello, this question may seem too basic to some, but please bear with be, it's been a while since I dealt with decent database programming. I have an algorithm that I need to program in PHP/MySQL to work on a website. It performs some computations iteratively on an array of objects (it ranks the objects based on their properties). In each iteration the algorithm runs through all collection a couple of times, accessing various data from different places of the whole collection. The algorithm needs several hundred iterations to complete. The array comes from a database. The straightforward solution that I see is to take the results of a database query and create an object for each row of the query, put the objects to an array and pass the array to my algorithm. However, I'm concerned with efficacy of such solution when I have to work with an array of several thousand of items because what I do is essentially mirror the results of a query to memory. On the other hand, making database query a couple of times on each iteration of the algorithm also seems wrong. So, my question is - what is the correct architectural solution for a problem like this? Is it OK to mirror the query results to memory? If not, which is the best way to work with query results in such an algorithm? Thanks!

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  • PHP dynamic Page-level DocBlocks

    - by Obmerk Kronen
    I was wondering if there is a way to interact with the Page-level DocBlocks. My question is more specifically about wordpress plugin development, but this question has arised also in a non-wordpress environments. The reason is mainly the possibility to easily change VERSIONS and names throughout a large project with maybe a constant definition - but that will reflect also in the docblock.. The following example Docblock is from a wordpress plugin I write - /* Plugin Name: o99 Auxilary Functions v0.4.7 Plugin URI: http://www.myurl.com Description: some simple description that nobody reads. Version: 0.4.7 Author: my cool name Author URI: http://www.ok-alsouri.com */ Is there a way to transform it into : $ver = '0.4.7'; $uri = 'http://www.myurl.com'; $desc = 'some simple description that nobody reads.'; $mcn = 'my cool name'; etc.. etc.. /* Plugin Name: o99 Auxilary Functions ($ver) Plugin URI: ($uri) Description: ($desc) Version: ($ver) Author: ($mcn) Author URI: ($$uri) */ obviously for echo to work I would need to break the docblock itself, and I can not WRITE the docblock directly into it´s own file . In shorts : can I "generate" a docblock with php itself somehow (I would think that the answer is - "no" for the page itself.. But maybe I am wrong and someone has some neat hack :-) ) Is that even possible ?

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  • Javascript Global Variable in Array

    - by user1387727
    My question may be very easy to lots of people, but I am new to Javascript. I really do not know what is wrong with the following codes. var newValue = 1; function getCurrentAmount() { return [newValue,2,3]; } var result = getCurrentAmount(); console.log(result[0] + "" + result[1] + result[2]); In the above code, the result shown in console is: undefined23 Why is the result not "123"? I am trying to use global variable because I want to increment newValue by 1 each time when the function is called. I want something like the following: var newValue = 1; function getCurrentAmount() { newValue ++; return [newValue,2,3]; } setInterval(function(){ var result = getCurrentAmount(); console.log(result[0] + "" + result[1] + result[2]); }, 1000); Also, I just tired the following codes and it works as expected. var newValue =1; function test() { newValue ++; return newValue; } console.log(test()); So I think the problem is about the Array. I hope my question is clear enough. Thanks in advance.

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  • Weird send() problem (with Wireshark log)

    - by Meta
    I had another question about this issue, but I didn't ask properly, so here I go again! I'm sending a file by sending it in chunks. Right now, I'm playing around with different numbers for the size of that chunk, to see what size is the most efficient. When testing on the localhost, any chunk size seems to work fine. But when I tested it over the network, it seems like the maximum chunk size is 8191 bytes. If I try anything higher, the transfer becomes extremely, painfully, slow. To show what happens, here are the first 100 lines of Wireshark logs when I use a chunk size of 8191 bytes, and when I use a chunk size of 8192 bytes: (the sender is 192.168.0.102, and the receiver is 192.168.0.100) 8191: http://pastebin.com/E7jFFY4p 8192: http://pastebin.com/9P2rYa1p Notice how in the 8192 log, on line 33, the receiver takes a long time to ACK the data. This happens again on line 103 and line 132. I believe this delay is the root of the problem. Note that I have not modified the SO_SNDBUF option nor the TCP_NODELAY option. So my question is, why am I getting delayed ACKs when sending files in chunks of 8192 bytes, when everything works fine when using chunks of 8191 bytes? Edit: As an experiment, I tried to do the file transfer in the other direction (from 192.168.0.100 to 192.168.0.102), and surprisingly, any number worked! (Although numbers around 8000 seemed to perform the smoothest). So then the problem is with my computer! But I'm really not sure what to check for. Edit 2: Here is the pseudocode I use to send and receive data.

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  • two view controllers and reusability with delegate

    - by netcharmer
    Newbie question about design patterns in objC. I'm writing a functionality for my iphone app which I plan to use in other apps too. The functionality is written over two classes - Viewcontroller1 and Viewcontroller2. Viewcontroller1 is the root view of a navigation controller and it can push Viewcontroller2. Rest of the app will use only ViewController1 and will never access Viewcontroller2 directly. However, triggered by user events, Viewcontroller2 has to send a message to the rest of the app. My question is what is the best way of achieving it? Currently, I use two level of delegation to send the message out from Viewcontroller2. First send it to Viewcontroller1 and then let Viewcontroller1 send it to rest of the app or the application delegate. So my code looks like - //Viewcontroller1.h @protocol bellDelegate -(int)bellRang:(int)size; @end @interface Viewcontroller1 : UITableViewController <dummydelegate> { id <bellDelegate> delegate; @end //Viewcontroller1.m @implementation Viewcontroller1 -(void)viewDidLoad { //some stuff here Viewcontroller2 *vc2 = [[Viewcontroller2 alloc] init]; vc2.delegate = self; [self.navigationController pushViewController:vc2 animated:YES]; } -(int)dummyBell:(int)size { return([self.delegate bellRang:size]); } //Viewcontroller2.h @protocol dummyDelegate -(int)dummyBell:(int)size; @end @interface Viewcontroller2 : UITableViewController { id <dummyDelegate> delegate; @end //Viewcontroller2.m @implementation Viewcontroller2 -(int)eventFoo:(int)size { rval = [self.delegate dummyBell:size]; } @end

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  • How do browser cookie domains work?

    - by Vilx-
    Due to weird domain/subdomain cookie issues that I'm getting, I'd like to know how browsers handle cookies. If they do it in different ways, it would also be nice to know the differences. In other words - when a browser receives a cookie, that cookie MAY have a domain and a path attached to it. Or not, in which case the browser probably substitutes some defaults for them. Question 1: what are they? Later, when the browser is about to make a request, it checks its cookies and filters out the ones it should send for that request. It does so by matching them against the requests path and domain. Question 2: what are the matching rules? Added: The reason I'm asking this is because I'm interested in some edge cases. Like: Will a cookie for .example.com be available for www.example.com? Will a cookie for .example.com be available for example.com? Will a cookie for example.com be available for www.example.com? Will a cookie for example.com be available for anotherexample.com? Will www.example.com be able to set cookie for example.com? Will www.example.com be able to set cookie for www2.example.com? Will www.example.com be able to set cookie for .com? Etc. Added 2: Also, could someone suggest how I should set a cookie so that: It can be set by either www.example.com or example.com; It is accessible by both www.example.com and example.com.

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  • Framework or CMS for php web development?

    - by rocknroll
    Hi all, I am a C++,Unix developer who has never dabbled in web development apart from creating simple HTML pages. I am going to change that and develop a website at a personal level soon. I am going to use php,mysql on a linux machine. In this regard I am browsing through relevant literature. The language isn't a problem but reading about CMS's and frameworks is confusing. And since I am new to web development, the number of CMS's and Frameworks are overwhelming. ? My question is do I need to have knowledge of one or more CMS' and/or Frameworks like Drupal,Joomla,Zend,Wordpress etc. If yes which is the best open source CMS' and/or Framework suggested for a newbie. ?? If the answer to the above question is yes, does the choice changes if one delves into the realms of commercial web development? Note:- I will be developing on a Linux machine, using open source tools. Thanks in advance

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  • How can I write output to a new external file with Perl?

    - by Structure
    Maybe I am searching with the wrong keywords or this is a very basic question but I cannot find the answer to my question. I am having trouble writing the result of my whois command to a new external file. My code is below. It takes $readfilename, which is a file name which has a list of IPs, and $writefilename, which is the destination file for output. Both are user-specified. For my tests, $readfilename contains three IP addresses on three separate lines so there should be three separate whois results in the user specified output file. if ($readfilename) { open (my $inputfile, "<", $readfilename) || die "\n Cannot open the specified file. Please double check your file name and path.\n\n"; open (my $outputfile, ">", $writefilename) || die "\n Could not create write file.\n\n"; while (<$inputfile>) { my $iplookupresult = `whois $_`; print $outputfile $iplookupresult; } close $outputfile; close $inputfile; } I can execute this script and end up with a new external file, but over half of the file has binary garbage data (running on CentOS) and only one (or a portion of one) of the whois lookups is readable. I have no idea how half of my file is ending up binary... but my approach must be incorrect. Is there a better way to achieve the same result?

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  • memcached: which is faster, doing an add (and checking result), or doing a get (and set when returni

    - by Mike Sherov
    The title of this question isn't so clear, but the code and question is straightforward. Let's say I want to show my users an ad once per day. To accomplish this, every time they visit a page on my site, I check to see if a certain memcache key has any data stored on it. If so, don't show an ad. If not, store the value '1' in that key with an expiration of 86400. I can do this 2 ways: //version a $key='OPD_'.date('Ymd').'_'.$type.'_'.$user; if($memcache->get($key)===false){ $memcache->set($key,'1',false,$expire); //show ad } //version b $key='OPD_'.date('Ymd').'_'.$type.'_'.$user; if($memcache->add($key,'1',false,$expire)){ //show ad } Now, it might seem obvious that b is better, it always makes 1 memcache call. However, what is the overhead of "add" vs. "get"? These aren't the real comparisons... and I just made up these numbers, but let's say 1 add ~= 1 set ~= 5 get in terms of effort, and the average user views 5 pages a day: a: (5 get * 1 effort) + (1 set * 5 effort) = 10 units of effort b: (5 add * 5 effort) = 25 units of effort Would it make sense to always do the add call? Is this an unnecessary micro-optimization?

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  • Is this a bad indexing strategy for a table?

    - by llamaoo7
    The table in question is part of a database that a vendor's software uses on our network. The table contains metadata about files. The schema of the table is as follows Metadata ResultID (PK, int, not null) MappedFieldname (char(50), not null) Fieldname (PK, char(50), not null) Fieldvalue (text, null) There is a clustered index on ResultID and Fieldname. This table typically contains millions of rows (in one case, it contains 500 million). The table is populated by 24 workers running 4 threads each when data is being "processed". This results in many non-sequential inserts. Later after processing, more data is inserted into this table by some of our in-house software. The fragmentation for a given table is at least 50%. In the case of the largest table, it is at 90%. We do not have a DBA. I am aware we desperately need a DB maintenance strategy. As far as my background, I'm a college student working part time at this company. My question is this, is a clustered index the best way to go about this? Should another index be considered? Are there any good references for this type and similar ad-hoc DBA tasks?

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  • scala 2.8 CanBuildFrom

    - by oxbow_lakes
    Following on from another question I asked, I wanted to understand a bit more about the Scala method TraversableLike[A].map whose signature is as follows: def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That Notice a few things about this method: it takes a function turning each A in the traversable into a B it returns That and takes an implicit argument of type CanBuildFrom[Repr, B, That] I can call this as follows: > val s: Set[Int] = List("Paris", "London").map(_.length) s: Set[Int] Set(5,6) What I cannot quite grasp is how the fact that That is bound to B (i.e. it is some collection of B's) is being enforced by the compiler. The type parameters look to be independent in both the signature above and in the signature of the trait CanBuildFrom itself: trait CanBuildFrom[-From, -Elem, +To] How is the scala compiler ensuring that That cannot be forced into something which does not make sense? > val s: Set[String] = List("Paris", "London").map(_.length) //will not compile EDIT - this question of course boils down to: How does the compiler decide what implicit CanBuildFrom objects are in scope for the call?

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  • Is there such a thing as a MemberExpression that handles a many-to-many relationship?

    - by Jaxidian
    We're trying to make it easy to write strongly-typed code in all areas of our system, so rather than setting var sortColumn = "FirstName" we'd like to say sortOption = (p => p.FirstName). This works great if the sortOption is of type Expression<Func<Person, object>> (we actually use generics in our code but that doesn't matter). However, we run into problems for many-to-many relationships because this notation breaks down. Consider this simple code: internal class Business { public IQueryable<Address> Addresses { get; set; } public string Name { get; set; } } internal class Address { public State MyState { get; set; } } internal class State { public string Abbreviation { get; set; } public int StateID { get; set; } } Is it possible to have this sort of MemberExpression to identify the StateID column off of a business? Again, the purpose of using this is not to return a StateID object, it's to just identify that property off of that entity (for sorting, filtering, and other purposes). It SEEMS to me that there should be some way to do this, even if it's not quite as pretty as foo = business.Addresses.SomeExtension(a => a.State.StateID);. Is this really possible? If more background is needed, take a look at this old question of mine. We've since updated the code significantly, but this should give you the general detailed idea of the context behind this question.

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  • What constitutes explicit creation of entities in LINQ to SQL? What elegant "solutions" are there to

    - by Marcelo Zabani
    Hi SO, I've been having problems with the rather famous "Explicit construction of entity type '##' in query is not allowed." error. Now, for what I understand, this exists because if explicit construction of these objects were allowed, tracking changes to the database would be very complicated. So I ask: What constitutes the explicit creation of these objects? In other terms: Why can I do this: Product foo = new Product(); foo.productName = "Something"; But can't do this: var bar = (from item in myDataContext.Products select new Product { productName = item.productName }).ToList(); I think that when running the LINQ query, some kind of association is made between the objects selected and the table rows retrieved (and this is why newing a Product in the first snippet of code is no problem at all, because no associations were made). I, however, would like to understand this a little more in depth (and this is my first question to you, that is: what is the difference from one snippet of code to another). Now, I've heard of a few ways to attack this problem: 1) The creation of a class that inherits the linq class (or one that has the same properties) 2) Selecting anonymous objects And this leads me to my second question: If you chose one of the the two approaches above, which one did you choose and why? What other problems did your approach introduce? Are there any other approaches?

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  • EF Query with conditional include that uses Joins

    - by makerofthings7
    This is a follow up to another user's question. I have 5 tables CompanyDetail CompanyContacts FK to CompanyDetail CompanyContactsSecurity FK to CompanyContact UserDetail UserGroupMembership FK to UserDetail How do I return all companies and include the contacts in the same query? I would like to include companies that contain zero contacts. Companies have a 1 to many association to Contacts, however not every user is permitted to see every Contact. My goal is to get a list of every Company regardless of the count of Contacts, but include contact data. Right now I have this working query: var userGroupsQueryable = _entities.UserGroupMembership .Where(ug => ug.UserID == UserID) .Select(a => a.GroupMembership); var contactsGroupsQueryable = _entities.CompanyContactsSecurity;//.Where(c => c.CompanyID == companyID); /// OLD Query that shows permitted contacts /// ... I want to "use this query inside "listOfCompany" /// //var permittedContacts= from c in userGroupsQueryable //join p in contactsGroupsQueryable on c equals p.GroupID //select p; However this is inefficient when I need to get all contacts for all companies, since I use a For..Each loop and query each company individually and update my viewmodel. Question: How do I shoehorn the permittedContacts variable above and insert that into this query: var listOfCompany = from company in _entities.CompanyDetail.Include("CompanyContacts").Include("CompanyContactsSecurity") where company.CompanyContacts.Any( // Insert Query here.... // b => b.CompanyContactsSecurity.Join(/*inner*/,/*OuterKey*/,/*innerKey*/,/*ResultSelector*/) ) select company; My attempt at doing this resulted in: var listOfCompany = from company in _entities.CompanyDetail.Include("CompanyContacts").Include("CompanyContactsSecurity") where company.CompanyContacts.Any( // This is concept only... doesn't work... from grps in userGroupsQueryable join p in company.CompanyContactsSecurity on grps equals p.GroupID select p ) select company;

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  • How is machine code understood by the machine

    - by Kraken
    I have a very naive question here, and I would like you to correct me on whatever wrong concepts I put out here. The question is as follows: I have ubuntu installed on my machine, now I write a helloWorld.c program in C language. Now, on the operating system I have a compiler installed, when I execute my helloWorld.c program, the OS schedules the compiler and that basically compiles my code into machine code, which eventually, I execute. Now my kernel code is written in C, then how does my machine interprets that code? Say my kernel code is helloWorld.c, now would not I require any compiler, to compile this code. Also, if I hardcode a compiler in maybe ROM or something, then what language is it written in? Assembly language? Let me know if I have made myself clear with the problem. Thanks. EDIT: By kernel code I mean, the code for operating system. Operating System code. I guess it is written in C right?

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  • Why should I install Python packages into `~/.local`?

    - by Matthew Rankin
    Background I don't develop using OS X's system provided Python versions (on OS X 10.6 that's Python 2.5.4 and 2.6.1). I don't install anything in the site-packages directory for the OS provided versions of Python. (The only exception is Mercurial installed from a binary package, which installs two packages in the Python 2.6.1 site-packages directory.) I installed three versions of Python, all using the Mac OS X installer disk image: Python 2.6.6 Python 2.7 Python 3.1.2 I don't like polluting the site-packages directory for my Python installations. So I only install the following five base packages in the site-packages directory. For the actual method/commands used to install these, see SO Question 4324558. setuptools/ez_setup distribute pip virtualenv virtualenvwrapper All other packages are installed in virtualenvs. I am the only user of this MacBook. Questions Given the above background, why should I install the five base packages in ~/.local? Since I'm installing these base packages into the site-packages directories of Python distributions that I've installed, I'm isolated from the OS X's Python distributions. Using this method, should I be concerned about Glyph's comment that other things could potentially break (see his comment below)? Again, I'm only interested in where to install those five base packages. Related Questions/Info I'm asking because of Glyph's comment to my answer to SO question 4314376, which stated: NO. NEVER EVER do sudo python setup.py install whatever. Write a ~/.pydistutils.cfg that puts your pip installation into ~/.local or something. Especially files named ez_setup.py tend to suck down newer versions of things like setuptools and easy_install, which can potentially break other things on your operating system. Previously, I asked What's the proper way to install pip, virtualenv, and distribute for Python?. However, no one answered the "why" of using ~/.local.

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