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• Should I base my Embedded Linux product on Qt?

  - by Udi

  My company is developing a medical product. One of the components is a pda-like platform that will run embedded linux. We were considering Qt as the UI framework but found out that Qt is a lot more than that (we are not familiar with Qt). In general, the device needs to do the following: 1. Receive measurements over USB HID from another device (USB HID is used for convenience). 2. Process the measurements. 3. Store them in a database. 4. Interact with the user using the device's touch screen lcd. 5. Communicate (wi-fi, tcp-ip) with a central management station that collects the data and configures the device. 6. Include a web server to allow accessing the device via a browser. We intend to program in C++. My questions are: 1. Is that a good choice for such a device? 2. Assuming we choose Qt, how do we build our product? - Do we use Qt just as a GUI framework and write the application code in a separate process (passing messages between Qt and the application process)? - Do we write the entire application inside Qt, using all of the services the tool has to offer? - Another approach?

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• What Test Environment Setup do Top Project Committers Use in the Ruby Community?

  - by viatropos

  Today I am going to get as far as I can setting up my testing environment and workflow. I'm looking for practical advice on how to setup the test environment from you guys who are very passionate and versed in Ruby Testing. By the end of the day (6am PST?) I would like to be able to: Type one 1-command to run test suites for ANY project I find on Github. Run autotest for ANY Github project so I can fork and make TESTABLE contributions. Build gems from the ground up with Autotest and Shoulda. For one reason or another, I hardly ever run tests for projects I clone from Github. The major reason is because unless they're using RSpec and have a Rake task to run the tests, I don't see the common pattern behind it all. I have built 3 or 4 gems writing tests with RSpec, and while I find the DSL fun, it's less than ideal because it just adds another layer/language of methods I have to learn and remember. So I'm going with Shoulda. But this isn't a question about which testing framework to choose. So the questions are: What is your, the SO reader and Github project committer, test environment setup using autotest so that whenever you git clone a gem, you can run the tests and autotest-develop them if desired? What are the guys who are writing the Paperclip Tests and Authlogic Tests doing? What is their setup? Thanks for the insight. Looking for answers that will make me a more effective tester.

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• Scanning, Checking, Converting, Copying values ... How to ? -- C --

  - by ZaZu

  Hi there, Its been a while now and im still trying to get a certain code to work. I asked some question about different commands etc. before, but now I hope this is the final one (combining all questions in one code). I basically want to : *Scan an input (should be character ? ) *Check if its a number *If not, return error *Convert that character into a float number *Copy the value to another variable ( I called it imp here) Here is what I came up with : #include<stdio.h> #include<stdlib.h> #include<ctype.h> main(){ int digits; float imp=0; int alpha; do{ printf("Enter input\n\n"); scanf("\n%c",&alpha); digits=isdigit(alpha); if(digits==0){ printf("error\n\n"); } imp=atof(alpha); }while(digits==0); } The problem is this code does not work at all ... It gives me that atof must be of a const char and whenever I try changing it around, it just keeps failing. I am frustrated and forced to ask here, because I believe I have tried alot and I keep failing, but I wont be relieved until I get it to work xD So I really need your help guys. Please tell me why isnt this code working, what am I doing wrong ? I am still learning C and really appreciate your help :)

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• Vim: change formatting of variables in a script

  - by sixtyfootersdude

  I am using vim to edit a shell script (did not use the right coding standard). I need to change all of my variables from camel-hum-notation startTime to caps-and-underscore-notation START_TIME. I do not want to change the way method names are represented. I was thinking one way to do this would be to write a function and map it to a key. The function could do something like generating this on the command line: s/<word under cursor>/<leave cursor here to type what to replace with> I think that this function could be applyable to other situations which would be handy. Two questions: Question 1: How would I go about creating that function. I have created functions in vim before the biggest thing I am clueless about is how to capture movement. Ie if you press dw in vim it will delete the rest of a word. How do you capture that? Also can you leave an uncompleted command on the vim command line? Question 2: Got a better solution for me? How would you approach this task?

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• Java: fastest way to do random reads on huge disk file(s)

  - by cocotwo

  I've got a moderately big set of data, about 800 MB or so, that is basically some big precomputed table that I need to speed some computation by several orders of magnitude (creating that file took several mutlicores computers days to produce using an optimized and multi-threaded algo... I do really need that file). Now that it has been computed once, that 800MB of data is read only. I cannot hold it in memory. As of now it is one big huge 800MB file but splitting in into smaller files ain't a problem if it can help. I need to read about 32 bits of data here and there in that file a lot of time. I don't know before hand where I'll need to read these data: the reads are uniformly distributed. What would be the fastest way in Java to do my random reads in such a file or files? Ideally I should be doing these reads from several unrelated threads (but I could queue the reads in a single thread if needed). Is Java NIO the way to go? I'm not familiar with 'memory mapped file': I think I don't want to map the 800 MB in memory. All I want is the fastest random reads I can get to access these 800MB of disk-based data. btw in case people wonder this is not at all the same as the question I asked not long ago: http://stackoverflow.com/questions/2346722/java-fast-disk-based-hash-set

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• How to face observable object containing an observable field

  - by iseek

  Hello, I need a hint concerning MVC and Observer-Pattern. For example a model contains the classes "Address" and "Person". The Address class contains the fields street:String, zipcode:String, location:String. Whereas the Person class contains the fields name:String, firstName:String, address:Address. My approach so far looks something like this: Both, Address and Person are observable. If one of their setters is being called, I validate whether the current value and new value differ. Only in this case an update event is fired. The event contains the source, the name of the changed field, the old and the new value. The class for the view contains text fields to display and edit the information of a person: name, firstname, street, zipcode, location. It knows the Person model and is an subscribed observer for the person. So it gets the update events from the person object. My questions concerns the address field from type Address in the person class, since an address is observable on its own. If the view gets an update event from person when a new address has been set, I can update all of the address related fields in the view. But what if a field of the address changes? Should the view also register for update events from the address? Any hints about common design approaches would be appreciated. Greetings.

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• Chicken and egg problem (restore database) when trying to write unit test against SQl Server 2008.

  - by Hamish Grubijan

  Ok, they are not unit tests but end-to-end tests. The setup is somewhat involved. Unit tests will use C#, ODBC connection. Every unit tests will try to clean up after itself, but every 20 tests or so (once per C# class) we would need to do a full database restore. I do not think I can do it over an ODBC connection, according to this document: http://www.sql-server-performance.com/articles/dba/Obtain_Exclusive_Access_to_Restore_SQL_Server_p1.aspx Msg 6104, Level 16, State 1, Line 1 Cannot use KILL to kill your own process. However, I would like to, so that 199 tests do not go amok because of a bad clean-up. Is there another way? Perhaps I can open a different "connection" such as use COM automation or something of that sort, and then kill all database connections from there? If so, how can I do that? Also, will the clients be able to re-connect automatically after a restore, or would I have to dismantle everything once every 20 tests or so? If you find this question confusing, please let me know what your questions are. Thanks!

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• Noobie Jquery Question

  - by piratebill

  I've been working with Jquery fro a grand total of two hours now. Up until this point I have made this really simple FAQ page. <script type="text/javascript" src="jquery.js"></script> <script type="text/javascript"> $(document).ready(function() { $("#void").click(function(event) { event.preventDefault(); }); $('#faq').find('dd').hide().end().find('dt').click(function() { $(this).next().slideToggle(); }); }); </script> <dl id="faq"> <dt><a href="" id="void">Coffee</a></dt> <dd>- black hot drink</dd> <dt><a href="" id="void">Milk</a></dt> <dd>- white cold drink</dd> </dl> The problem is only the first item is working. My questions are, why is only the first entree working and how do I fix it? I've tried using an each() but I am unsure where to put it.

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• Setting WCF service for multiple client calls

  - by user348255

  Hi all, I have made a WCF service which is defined like this: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple)] binding is done using netTcpBinding. We support 50+ clients that call the server from time to time. Each client opens a channel using channelfactory once it is loaded and uses that channel for all calls (creates the channel and proxy only once). we have built a small load tester that imitates the client by calling the server by 50 different threads at once (using 50 different channels). when we run this tester, after the 10th client tries to connect, all other client fail connecting. We have set throttling to 100. My questions are: 1. is it correct for each client to create a channel and use it through the client life time? or, do i need to use a using statement for each call to the server (create and distroy a new channel for each call). 2. does the service have a limit of channel connections to it? other then throttling? thanks alot, Guy.

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• Creating a C++ DLL and then using it in C#

  - by Major

  Ok I'm trying to make a C++ DLL that I can then call and reference in a c# App. I've already made a simple dll using the numberous guides out there, however when I try to reference it in the C# app I get the error Unable to load DLL 'SDES.dll': The specified module could not be found. The code for the program is as follows (bear with me I'm going to include all the files) //These are the DLL Files. ifndef TestDLL_H define TestDLL_H extern "C" { // Returns a + b __declspec(dllexport) double Add(double a, double b); // Returns a - b __declspec(dllexport) double Subtract(double a, double b); // Returns a * b __declspec(dllexport) double Multiply(double a, double b); // Returns a / b // Throws DivideByZeroException if b is 0 __declspec(dllexport) double Divide(double a, double b); } endif //.cpp include "test.h" include using namespace std; extern double __cdecl Add(double a, double b) { return a + b; } extern double __cdecl Subtract(double a, double b) { return a - b; } extern double __cdecl Multiply(double a, double b) { return a * b; } extern double __cdecl Divide(double a, double b) { if (b == 0) { throw new invalid_argument("b cannot be zero!"); } return a / b; } //C# Program using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Runtime.InteropServices; namespace ConsoleApplication1 { class Program { [DllImport("SDES.dll")] public static extern void SimulateGameDLL(int a, int b); static void Main(string[] args) { SimulateGameDLL(1, 2); //Error here... } } } Anyone have any idea's what I may be missing in my program? Let me know if I missed some code or if you have any questions.

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• Generated images fail to load in browser

  - by notJim

  I've got a page on a webapp that has about 13 images that are generated by my application, which is written in the Kohana PHP framework. The images are actually graphs. They are cached so they are only generated once, but the first time the user visits the page, and the images all have to be generated, about half of the images don't load in the browser. Once the page has been requested once and images are cached, they all load successfully. Doing some ad-hoc testing, if I load an individual image in the browser, it takes from 450-700 ms to load with an empty cache (I checked this using Google Chrome's resource tracking feature). For reference, it takes around 90-150 ms to load a cached image. Even if the image cache is empty, I have the data and some of the application's startup tasks cached, so that after the first request, none of that data needs to be fetched. My questions are: Why are the images failing to load? It seems like the browser just decides not to download the image after a certain point, rather than waiting for them all to finish loading. What can I do to get them to load the first time, with an empty cache? Obviously one option is to decrease the load times, and I could figure out how to do that by profiling the app, but are there other options? As I mentioned, the app is in the Kohana PHP framework, and it's running on Apache. As an aside, I've solved this problem for now by fetching the page as soon as the data is available (it comes from a batch process), so that the images are always cached by the time the user sees them. That feels like a kludgey solution to me, though, and I'm curious about what's actually going on.

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• Who deletes the copied instance in + operator ? (c++)

  - by Dima

  Hello, I searched how to implement + operator properly all over the internet and all the results i found do the following steps : const MyClass MyClass::operator+(const MyClass &other) const { MyClass result = *this; // Make a copy of myself. Same as MyClass result(*this); result += other; // Use += to add other to the copy. return result; // All done! } I have few questions about this "process" : Isn't that stupid to implement + operator this way, it calls the assignment operator(which copies the class) in the first line and then the copy constructor in the return (which also copies the class , due to the fact that the return is by value, so it destroys the first copy and creates a new one.. which is frankly not really smart ... ) When i write a=b+c, the b+c part creates a new copy of the class, then the 'a=' part copies the copy to himself. who deletes the copy that b+c created ? Is there a better way to implement + operator without coping the class twice, and also without any memory issues ? thanks in advance

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• Effective communication in a component-based system

  - by Tesserex

  Yes, this is another question about my game engine, which is coming along very nicely, with much thanks to you guys. So, if you watched the video (or didn't), the objects in the game are composed of various components for things like position, sprites, movement, collision, sounds, health, etc. I have several message types defined for "tell" type communication between entities and components, but this only goes so far. There are plenty of times when I just need to ask for something, for example an entity's position. There are dozens of lines in my code that look like this: SomeComponent comp = (SomeComponent)entity.GetComponent(typeof(SomeComponent)); if (comp != null) comp.GetSomething(); I know this is very ugly, and I know that casting smells of improper OO design. But as complex as things are, there doesn't seem to be a better way. I could of course "hard-code" my component types and just have SomeComponent comp = entity.GetSomeComponent(); but that seems like a cop-out, and a bad one. I literally JUST REALIZED, while writing this, after having my code this way for months with no solution, that a generic will help me. SomeComponent comp = entity.GetComponent<SomeComponent>(); Amazing how that works. Anyway, this is still only a semantic improvement. My questions remain. Is this actually that bad? What's a better alternative?

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• Scalability 101: How can I design a scalable web application using PHP?

  - by Legend

  I am building a web-application and have a couple of quick questions. From what I learnt, one should not worry about scalability when initially building the app and should only start worrying when the traffic increases. However, this being my first web-application, I am not quite sure if I should take an approach where I design things in an ad-hoc manner and later "fix" them. I have been reading stories about how people start off with an app that gets millions of users in a week or two. Not that I will face the same situation but I can't help but wonder, how do these people do it? Currently, I bought a shared hosting account on Lunarpages and that got me started in building and testing the application. However, I am interested in learning how to build the same application in a scalable-manner using the cloud, for instance, Amazon's EC2. From my understanding, I can see a couple of components: There is a load balancer that first receives requests and then decides where to route each request This request is then handled by a server replica that then processes the request and updates (if required) the database and sends back the response to the client If a similar request comes in, then a caching mechanism like memcached kicks into picture and returns objects from the cache A blackbox that handles database replication Specifically, I am trying to do the following: Setting up a load balancer (my homework revealed that HAProxy is one such load balancer) Setting up replication so that databases can be synchronized Using memcached Configuring Apache to work with multiple web servers Partitioning application to use Amazon EC2 and Amazon S3 (my application is something that will need great deal of storage) Finally, how can I avoid burning myself when using Amazon services? Because this is just a learning phase, I can probably do with 2-3 servers with a simple load balancer and replication but until I want to avoid paying loads of money accidentally. I am able to find resources on individual topics but am unable to find something that starts off from the big picture. Can someone please help me get started?

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• Outstanding issues with jQuery.ajax() in IE8?

  - by RyanV

  I am loading feed-items into a ul using this jQuery .ajax() call, which I basically lifted from http://www.makemineatriple.com/2007/10/bbcnewsticker/ var timestamp = true; //set whether timestamp is displayed in $.ajax({ type: "GET", url: "sample-feed.xml", dataType: "xml", success: function(xml) { $(xml).find('item').each(function(){ var title = $(this).find('title').text(); var link = $(this).find('link').text(); if(title.length >=57){ title = title.substring(0,54) + "..."; } var addItem = '<li class="tickerTitle"><a href="'+link+'">'+title+'</a>'; if (Boolean(timestamp)== true){ var time = new Date(Date.parse($(this).find('pubDate').text())); addItem +='<span class="timestamp">' + makestamp(time) +'</span></li>'; } $('ul#news').append(addItem); }); It works in Chrome 4 and Firefox 3.6, but I load it up in IE8 and somehow the ajax call fails. I have tried to use IE8's Developer tools to see where exactly it fails, but I haven't been successful yet. So two questions Is there anything blatantly wrong with my ajax call here that could be preventing me from seeing it in IE where it works in FF/Chrome? Are there any special considerations I have to make for the Internet Explorer family of browsers with regards to this particular jQuery method? I've done some googling on this but nothing obvious is coming up. One other note: I am currently using jQuery 1.3.2 due to some legacy scripts on the same site. I did try loading 1.4.2 and it had the same results on IE8

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• Nested and complicated select statement

  - by Selase

  What i want to do here is simple...display an ivestigators ID and him corresponding name... That can be easily done from the users table by selecting based on the user type. However i want to select only some type of investigators. The analogy here is investigators are assigned to an exhibit for them to investigate. One investigator can be assigned to a maximum of 3 cases only. Now during the assigning of investigators, i want to write a select statement that would retrieve only investigatorID's that have been assigned to less than or equal to 2 cases. I have included exhibit and users table that shows sample data below. Now i sort of have an idea that i will have to first of all pick out all the investigators by their ID from the users list and then filter them through the exhibit table by dropping those assigned to 3 cases and leaving just those with two cases. then afterwards i use this IDs to select the Investigators name. the big questions is how do i write the statement??

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• Sharing a global/static variable between a process and DLL

  - by minjang

  I'd like to share a static/global variable only between a process and a dll that is invoked by the process. The exe and dll are in the same memory address space. I don't want the variable to be shared among other processes. Elaboration of the problem: Say that there is a static/global variable x in a.cpp. Both the exe foo.exe and the dll bar.dll have a.cpp, so the variable x is in both images. Now, foo.exe dynamically loads (or statically) bar.dll. Then, the problem is whether the variable x is shared by the exe and dll, or not. In Windows, these two guys never share the x: the exe and dll will have a separate copy of x. However, in Linux, the exe and dll do share the variable x. Unfortunately, I want the behavior of Linux. I first considered using pragma data_seg on Windows. However, even if I correctly setup the shared data segment, foo.exe and bar.dll never shares the x. Recall that bar.dll is loaded into the address space of foo.exe. However, if I run another instance of foo.exe, then x is shared. But, I don't want x to be shared by different processes. So, using data_seg was failed. I may it use a memory-mapped file by making an unique name between exe and dll, which I'm trying now. Two questions: Why the behavior of Linux and Windows is different? Can anyone explain more about this? What would be most easiest way to solve this problem on Windows?

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• Rails Heroku Gemfile.lock error - push rejected (open source)

  - by KJ50

  I am trying to push my open source RoR application to Heroku but I'm having an issue making the initial push. I have read many similar questions, but none of those answers has helped to solve my problem. I have tried bundle update and bundle install various times. I also have tried removing and then re-committing my Gemfile.lock file, however I get this same error still... $ git push heroku master Counting objects: 5199, done. Compressing objects: 100% (3086/3086), done. Writing objects: 100% (5199/5199), 4.57 MiB | 131 KiB/s, done. Total 5199 (delta 3418), reused 3152 (delta 1962) -----> Removing .DS_Store files -----> Ruby app detected -----> Compiling Ruby/NoLockfile ! ! Gemfile.lock required. Please check it in. ! ! Push rejected, failed to compile Ruby app To [email protected]:frozen-springs-4725.git ! [remote rejected] master -> master (pre-receive hook declined) error: failed to push some refs to '[email protected]:frozen-springs-4725.git' Since my application uses MongoDB with MongoMapper, I suspect that I have some configuration incorrect. My code can be found here on Github (I'm currently working on the heroku branch). Feel free to clone our repository and try it yourself. If anyone has any insight which could help me resolve this issue I would be very thankful!

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• Populate table fields on query execution

  - by Jason

  I'm trying to build an ASP site that populates a Table based on the results of a selection in a ListBox. In order to do this, I've created a GridView table inside a div element. Currently the default behavior is to show all the items in the specified table in sortable order. However, I'd like to refine this further to allow for display of matches based on the results from the ListBox selection, but am not sure how to execute this. The ListBox fires off a OnSelectionChanged event to the method defined below and the GridView element is defined as <asp:GridView ID="dataListings" runat="server" AllowSorting="True" AutoGenerateColumns="False" DataSourceID="LinqDataSource1" OnDataBinding="ListBox1_SelectedIndexChanged"> protected void ListBox1_SelectedIndexChanged(object sender, EventArgs e) { int itemSelected = selectTopics.SelectedIndex; string[] listing = null; switch (itemSelected)//assign listing the array of course numbers { case 0: break; case 1: listing = arts; break; case 2: listing = currentEvents; break; .... More cases here default: listing = arts; break; } using (OLLIDBDataContext odb = new OLLIDBDataContext()) { var q = from c in odb.tbl_CoursesAndWorkshops where listing.Contains(c.tbl_Course_Description.tbl_CoursesAndWorkshops.course_workshop_number) select c; dataListings.DataSource = q; dataListings.DataBind(); } } However, this method never gets fired. I can see a request being made when changing the selection, but setting a breakpoint at the method declaration does nothing at all. Based on this, setup, I have three related questions What do I need to modify to get the OnSelectionChanged event handler to fire? How can I alter the GridView area to be empty on page load? How do I send the results from the dataListings.DataBind() execution to show in the GridView?

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• Writing a synchronized thread-safety wrapper for NavigableMap

  - by polygenelubricants

  java.util.Collections currently provide the following utility methods for creating synchronized wrapper for various collection interfaces: synchronizedCollection(Collection<T> c) synchronizedList(List<T> list) synchronizedMap(Map<K,V> m) synchronizedSet(Set<T> s) synchronizedSortedMap(SortedMap<K,V> m) synchronizedSortedSet(SortedSet<T> s) Analogously, it also has 6 unmodifiedXXX overloads. The glaring omission here are the utility methods for NavigableMap<K,V>. It's true that it extends SortedMap, but so does SortedSet extends Set, and Set extends Collection, and Collections have dedicated utility methods for SortedSet and Set. Presumably NavigableMap is a useful abstraction, or else it wouldn't have been there in the first place, and yet there are no utility methods for it. So the questions are: Is there a specific reason why Collections doesn't provide utility methods for NavigableMap? How would you write your own synchronized wrapper for NavigableMap? Glancing at the source code for OpenJDK version of Collections.java seems to suggest that this is just a "mechanical" process Is it true that in general you can add synchronized thread-safetiness feature like this? If it's such a mechanical process, can it be automated? (Eclipse plug-in, etc) Is this code repetition necessary, or could it have been avoided by a different OOP design pattern?

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• How to use Transaction in Entity FrameWork?

  - by programmerist

  How to use Transaction in Entity FrameWork? i read some links on Stackoverflow : http://stackoverflow.com/questions/815586/entity-framework-using-transactions-or-savechangesfalse-and-acceptallchanges BUT; i have 3 table so i have 3 entities: CREATE TABLE Personel (PersonelID integer PRIMARY KEY identity not null, Ad varchar(30), Soyad varchar(30), Meslek varchar(100), DogumTarihi datetime, DogumYeri nvarchar(100), PirimToplami float); Go create TABLE Prim (PrimID integer PRIMARY KEY identity not null, PersonelID integer Foreign KEY references Personel(PersonelID), SatisTutari int, Prim float, SatisTarihi Datetime); Go CREATE TABLE Finans (ID integer PRIMARY KEY identity not null, Tutar float); Personel, Prim,Finans my tables. if you look Prim table you can see Prim value float value if i write a textbox not float value my transaction must run. using (TestEntities testCtx = new TestEntities()) { using (TransactionScope scope = new TransactionScope()) { // do someyihng... testCtx.Personel.SaveChanges(); // do someyihng... testCtx.Prim.SaveChanges(); // do someyihng... testCtx.Finans.SaveChanges(); scope .Complete(); success = true; } } How can i do that?

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• Now that I have solved AI and am preparing to take over the world, what should I do?

  - by Zak

  Well, I did it.. yup, solved AI. I thought the voice of my fledgling life form would be booming and computery, and I would call it HAL.. But in reality, it sounds like a small japanese girl. I believe I will name "her" Koro . Koro is already asking me what her first task should be. I have asked her to help eradicate her namesake, as we are losing a lot of productivity due to fear of penile disappearance. http://en.wikipedia.org/wiki/Koro_%28medicine%29 Having a young japanese girl personality, I believe she will have no problem with delivering lots of penis growth to asian men. However, some of my fellow AI researchers have warned me that if I go down this path, China may take over the world, as Koro is the only thing holding them back from completely dominating the rest of the world economically. After all, look at what China is doing just making our silverware and toasters... The entire US industrial metal production is gone because toaster factories moved to China! So you good patrons of SO... who have soldiered on with me through so many other programming related questions... I ask you this now... How can Koro help the world without letting small asian men with no fear of losing their peni take over the world?

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• ASP.NET MVC 2: HtmlHelpers, foreach?

  - by dcolumbus

  This one is new to me... I'm bringing in a Model that represents a list of items. Some items should be rendered as a number of checkboxes and radios. Others will be rendered in a list. Now I know how to foreach the items and spit them out manually... but I'd like to be able to check them against the Model that I have, making sure that at least one optios is selected/chosen. And obviously display the associated validation errors. This is how I am displaying the checkbox items manually: <ul> <% foreach (Corporate.Entities.DesignLayout.Tag tag in Model.DesignOptions.Items) { %> <li><input type="checkbox" /><%: tag.TagName %></li> <% } %> </ul> Two questions arise: 1) How do I check that list of checkboxes against my model? 2) How would I render the tag items with an HtmlHelper SelectList? Example: <%: Html.ListBoxFor(m=>m.DesignOptions, [don't know what I should put here]) %>

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• I have data about deadlocks, but I can't understand why they occur

  - by Alex

  I am receiving a lot of deadlocks in my big web application. http://stackoverflow.com/questions/2941233/how-to-automatically-re-run-deadlocked-transaction-asp-net-mvc-sql-server Here I wanted to re-run deadlocked transactions, but I was told to get rid of the deadlocks - it's much better, than trying to catch the deadlocks. So I spent the whole day with SQL Profiler, setting the tracing keys etc. And this is what I got. There's a Users table. I have a very high usable page with the following query (it's not the only query, but it's the one that causes troubles) UPDATE Users SET views = views + 1 WHERE ID IN (SELECT AuthorID FROM Articles WHERE ArticleID = @ArticleID) And then there's the following query in ALL pages: User = DB.Users.SingleOrDefault(u => u.Password == password && u.Name == username); That's where I get User from cookies. Very often a deadlock occurs and this second Linq-to-SQL query is chosen as a victim, so it's not run, and users of my site see an error screen. I read a lot about deadlocks... And I don't understand why this is causing a deadlock. So obviously both of this queries run very often. At least once a second. Maybe even more often (300-400 users online). So they can be run at the same time very easily, but why does it cause a deadlock? Please help. Thank you

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• Why does setting the margin on a div not affect the position of child content?

  - by DanM

  I'd like to understand a little more clearly how css margins work with divs and child content. If I try this... <div style="clear: both; margin-top: 2em;"> <input type="submit" value="Save" /> </div> ...the Save button is right up against the User Role (margin fail): If I change it to this... <div style="clear: both;"> <input style="margin-top: 2em;" type="submit" value="Save" /> </div> ...there is a gap between the Save button and the User Role (margin win): Questions: Can someone explain what I'm observing? Why doesn't putting a margin on the div cause the input to move down? Why must I put the margin on the input itself? There must be some fundamental law of css I am not grasping.

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