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• import csv file/excel into sql database asp.net

  - by kiev

  Hi everyone! I am starting a project with asp.net visual studio 2008 / SQL 2000 (2005 in future) using c#. The tricky part for me is that the existing DB schema changes often and the import files columns will all have to me matched up with the existing db schema since they may not be one to one match on column names. (There is a lookup table that provides the tables schema with column names I will use) I am exploring different ways to approach this, and need some expert advice. Is there any existing controls or frameworks that I can leverage to do any of this? So far I explored FileUpload .NET control, as well as some 3rd party upload controls to accomplish the upload such as SlickUpload but the files uploaded should be < 500mb Next part is reading of my csv /excel and parsing it for display to the user so they can match it with our db schema. I saw CSVReader and others but for excel its more difficult since I will need to support different versions. Essentially The user performing this import will insert and/or update several tables from this import file. There are other more advance requirements like record matching but and preview of the import records, but I wish to get through understanding how to do this first. Update: I ended up using csvReader with LumenWorks.Framework for uploading the csv files.

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• What is the fastest way to find duplicates in multiple BIG txt files?

  - by user2950750

  I am really in deep water here and I need a lifeline. I have 10 txt files. Each file has up to 100.000.000 lines of data. Each line is simply a number representing something else. Numbers go up to 9 digits. I need to (somehow) scan these 10 files and find the numbers that appear in all 10 files. And here comes the tricky part. I have to do it in less than 2 seconds. I am not a developer, so I need an explanation for dummies. I have done enough research to learn that hash tables and map reduce might be something that I can make use of. But can it really be used to make it this fast, or do I need more advanced solutions? I have also been thinking about cutting up the files into smaller files. To that 1 file with 100.000.000 lines is transformed into 100 files with 1.000.000 lines. But I do not know what is best: 10 files with 100 million lines or 1000 files with 1 million lines? When I try to open the 100 million line file, it takes forever. So I think, maybe, it is just too big to be used. But I don't know if you can write code that will scan it without opening. Speed is the most important factor in this, and I need to know if it can be done as fast as I need it, or if I have to store my data in another way, for example, in a database like mysql or something. Thank you in advance to anybody that can give some good feedback.

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• What's the most efficient way to load data from a file to a collection on-demand?

  - by Dan

  I'm working on a java project that will allows users to parse multiple files with potentially thousands of lines. The information parsed will be stored in different objects, which then will be added to a collection. Since the GUI won't require to load ALL these objects at once and keep them in memory, I'm looking for an efficient way to load/unload data from files, so that data is only loaded into the collection when a user requests it. I'm just evaluation options right now. I've also thought of the case where, after loading a subset of the data into the collection, and presenting it on the GUI, the best way to reload the previously observed data. Re-run the parser/Populate collection/Populate GUI? or probably find a way to keep the collection into memory, or serialize/deserialize the collection itself? I know that loading/unloading subsets of data can get tricky if some sort of data filtering is performed. Let's say that I filter on ID, so my new subset will contain data from two previous analyzed subsets. This would be no problem is I keep a master copy of the whole data in memory. I've read that google-collections are good and efficient when handling big amounts of data, and offer methods that simplify lots of things so this might offer an alternative to allow me to keep the collection in memory. This is just general talking. The question on what collection to use is a separate and complex thing. Do you know what's the general recommendation on this type of task? I'd like to hear what you've done with similar scenarios. I can provide more specifics if needed.

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• Java Generic Type and Reflection

  - by Tom Tucker

  I have some tricky generic type problem involving reflection. Here's the code. public @interface MyConstraint { Class<? extends MyConstraintValidator<?>> validatedBy(); } public interface MyConstraintValidator<T extends Annotation> { void initialize(T annotation); } /** @param annotation is annotated with MyConstraint. */ public void run(Annotation annotation) { Class<? extends MyConstraintValidator<? extends Annotation>> validatorClass = annotation.annotationType().getAnnotation(MyConstraint.class).validatedBy(); validatorClass.newInstance().initialize(annotation) // will not compile! } The run() method above will not compile because of the following error. The method initialize(capture#10-of ? extends Annotation) in the type MyConstraintValidator<capture#10-of ? extends Annotation> is not applicable for the arguments (Annotation) If I remove the wild cards, then it compiles and works fine. What would be the propert way to declare the type parameter for the vairable validatorClass? Thanks.

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• MySql Check if NOW() falls within a weekday/time range

  - by Niall

  I have a table as follows: CREATE TABLE `zonetimes` ( `id` int(11) unsigned NOT NULL AUTO_INCREMENT, `zone_id` int(10) unsigned NOT NULL, `active_from_day` tinyint(1) unsigned NOT NULL DEFAULT '2', `active_to_day` tinyint(1) unsigned NOT NULL DEFAULT '2', `active_from` time NOT NULL, `active_to` time NOT NULL PRIMARY KEY (`id`) ) ENGINE=MyISAM ; So, a user could add a time entry starting on a particular day and time and ending on a particular day and time, eg: Between Monday 08:00 and Friday 18:00 or Between Thursday 15:00 and Tuesday 15:00 (Note the crossover at the end of the week). I need to query this data and determine if a zone is currently active (NOW(), DAYOFWEEK() etc)... This is turning out to be quite tricky. If I didn't have overlaps, eg: from 'Wednesday 8pm to Tuesday 4am' or from 'Thursday 4pm to Tuesday 4pm' this would be easy with BETWEEN. Also, need to allow a user to add for the entire week, eg: Monday 8am - Monday 8am (This should be easy enough, eg: where (active_from_day=active_to_day AND active_from=active_to) OR .. Any ideas? Note: I found a similar question here Timespan - Check for weekday and time of day in mysql but it didn't get an answer. One of the suggestions was to store each day as a separate row. I would much rather store one time span for multiple days though.

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• How to reorder table rows (drag-and-drop) along with their sub rows

  - by Eirik Johansen

  I have a table which looks like this (simplified for the example): <table> <tr class="lvl_1"> <td> Level 1 </td> </tr> <tr class="lvl_2"> <td> Level 2 </td> </tr> <tr class="lvl_3"> <td> Level 3 </td> </tr> <tr class="lvl_1"> <td> Level 1 </td> </tr> <tr class="lvl_2"> <td> Level 2 </td> </tr> <tr class="lvl_3"> <td> Level 3 </td> </tr> The content in the rows with the lvl_3 class are children of the previous lvl_2 row, and the lvl_2 rows are children of the previous lvl_1. Had the data been a list, it would have looked something like this: Level 1 -- Level 2 ---- Level 3 Level 1 -- Level 2 ---- Level 3 I'm not looking to implement drag-and-drop sorting functionality, make it possible to rearrange the level 1 and two rows. The tricky part is that once I start moving a row, the corresponding children (and grand-children, if any) should move along with it. Is this even possible with the current markup, or do I have to rearrange the code? Thanks in advance !

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• Database choices

  - by flobadob

  I have a prickly design issue regarding the choice of database technologies to use for a group of new applications. The final suite of applications would have the following database requirements... Central databases (more than one database) using mysql (myst be mysql due to justhost.com). An application to be written which accesses the multiple mysql databases on the web host. This application will also write to local serverless database (sqlite/firebird/vistadb/whatever). Different flavors of this application will be created for windows (.NET), windows mobile, android if possible, iphone if possible. So, the design task is to minimise the quantity of code to achieve this. This is going to be tricky since the languages used are already c# / java (android) and objc (iphone). Not too worried about that, but can the work required to implement the various database access layers be minimised? The serverless database will hold similar data to the mysql server, so some kind of inheritance in the DAL would be useful. Looking at hibernate/nhibernate and there is linq to whatever. So many choices!

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• Activator.CreateInstance uses a huge amount of memory

  - by Marco

  I have been playing a bit with Silverlight and try to port my Silverlight 3.0 application to Silverlight 4.0. My application loads different XAP files and upon a user request create an instance of a Xaml user control and adds it to the main container, in a sort of MEF approach in order I can have an extensible and pluggable application. The application is pretty huge and to keep acceptable the performances and the initial loading I have built up some helper classes to load in the background all pages and user controls that might be used later on. On Silverlight 3.0 everything was running smoothly without any problem so far. Switching to SL 4.0 I have noticed that when the process approaches to create the instances of the user controls using Activator.CreateInstance, the layout freezes unexpectedly for a minute and sometimes for more. Looking at the task manager the memory usage of IE jumps from 50MB to 400MB and sometimes to 1.5 GB. If the process won't take that much the layout is rendered properly and the memory falls back to 50 MB. Otherwise everything crashes due to out of memory exeption. Does anybody encountered the same problem? Or has anybody a solution about this tricky issue?

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• @dynamic property needs setter with multiple behaviors

  - by ambertch

  I have a class that contains multiple user objects and as such has an array of them as an instance variable: NSMutableArray *users; The tricky part is setting it. I am deserializing these objects from a server via Objective Resource, and for backend reasons users can only be returned as a long string of UIDs - what I have locally is a separate dictionary of users keyed to UIDs. Given the string uidString of comma separated UIDs I override the default setter and populate the actual user objects: @dynamic users; - (void)setUsers:(id)uidString { users = [NSMutableArray arrayWithArray: [[User allUsersDictionary] objectsForKeys:[(NSString*)uidString componentsSeparatedByString:@","]]]; } The problem is this: I now serialize these to database using SQLitePO, which stores these as the array of user objects, not the original string. So when I retrieve it from database the setter mistakenly treats this array of user objects as a string! Where I actually want to adjust the setter's behavior when it gets this object from DB vs. over the network. I can't just make the getter serialize back into a string without tearing up large code that reference this array of user objects, and I tried to detect in the setter whether I have a string or an array coming in: if ([uidString respondsToSelector:@selector(addObject)]) { // Already an array, so don't do anything - just assign users = uidString but no success... so I'm kind of stuck - any suggestions? Thanks in advance!

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• Practical non-image based CAPTCHA approaches?

  - by Jeff Atwood

  It looks like we'll be adding CAPTCHA support to Stack Overflow. This is necessary to prevent bots, spammers, and other malicious scripted activity. We only want human beings to post or edit things here! We'll be using a JavaScript (jQuery) CAPTCHA as a first line of defense: http://docs.jquery.com/Tutorials:Safer_Contact_Forms_Without_CAPTCHAs The advantage of this approach is that, for most people, the CAPTCHA won't ever be visible! However, for people with JavaScript disabled, we still need a fallback and this is where it gets tricky. I have written a traditional CAPTCHA control for ASP.NET which we can re-use. However, I'd prefer to go with something textual to avoid the overhead of creating all these images on the server with each request. I've seen things like.. ASCII text captcha: \/\/(_)\/\/ math puzzles: what is 7 minus 3 times 2? trivia questions: what tastes better, a toad or a popsicle? Maybe I'm just tilting at windmills here, but I'd like to have a less resource intensive, non-image based <noscript> compatible CAPTCHA if possible. Ideas?

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• How can I determine when an InnoDB table was last changed?

  - by David M

  I've had success in the past storing the (heavily) processed results of a database query in memcached, using the last update time of the underlying tables(s) as part of the cache key. For MyISAM tables, that last changed time is available in SHOW TABLE STATUS. Unfortunately, that's usually NULL for InnoDB tables. In MySQL 4.1, the ctime for an InnoDB in its SHOW TABLE STATUS line was usually its actual last update time, but that doesn't seem to be true for MySQL 5.1. There is a DATETIME field in the table, but it only shows when a row has been modified - it cannot show the deletion time of a row that's not there anymore! So, I really cannot use MAX(update_time). Here's the really tricky part. I have a number of replicas that I do reads from. Can I figure out the state of the table that doesn't rely on when the changes have actually been applied? My conclusion after working on this for a while is that it's not going to be possible to get this information as cheaply as I'd like. I'm probably going to cache data until the time that I expect the table to change (it's updated once a day), and let the query cache help out where it can.

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• Jquery tabs with cookie support restore wrong tab position after page refresh.

  - by zenonych

  Hello, all. I have tricky problem which I can't completely understand... It's jquery tabs with cookie support. I've following code: $(document).ready(function() { var $tabs = $("#tabs").tabs(); $tabs.tabs('select', $.cookie("tabNumber")); $('#tabs ul li a').click(function() { $.cookie("tabNumber", $tabs.tabs('option', 'selected')); }); $('#btnSelect').click(function() { //alert($.cookie("tabNumber")); //$tabs.tabs('select', 2); $tabs.tabs('select', $.cookie("tabNumber")); }); }); So, I've 3 tabs (with positions 0,1,2) inside div named "tabs". When user selects one tab, then tab position stores in cookie. After that if user refresh page, active tab position must be restored. But each time I refresh page I get active tab in previous position (if I select 2nd tab, then after refresh I got active tab in position 1, etc.). I add some test in code (button btnSelect with onclick handler which duplicates load position functionality). So, if I uncomment and use $tabs.tabs('select', 2); Then after I click btnSelect I've got right position. Ok, that's right. Then I comment that line and uncomment next one: alert($.cookie("tabNumber")); So, I select tab, click button, get dialog message "2", and after that tab in position 1 became active. Why?? In both cases I call 'select' method with parameter 2... I know I can use aliases for tabs, but I want to understate why my code doesn't work properly.

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• How to make cycle over cycles in Java?

  - by Roman

  I would like to make a cycle over the following elements: [1,2,11,12,21,22,111,112,121,122,....,222222] or for example [1,2,3,11,12,13,21,22,23,31,32,33,111,112,113,... 333333333] How can I make it in Java? In my particular case I use 4 digits (1,2,3,4) and the length of the last number can be from 1 to 10. I managed to do it in Python and PHP. In the first case I used list over lists. I started from [[1],[2],] then for every element of the list I added 1 and 2, so I got [[1,1],[1,2],[2,1],[2,2]] and so on: nchips = sum(chips) traj = [[]] last = [[]] while len(last[0]) < nchips: newlast = [] for tr in last: for d in [1,2,3,4]: newlast.append(tr + [d]) last = newlast traj += last When I did it in PHP I used number with base 3. But it was a tricky and non elegant solution. for ($i=-1; $i<=$n; $i+=1) { if ($i>-1) { $n5 = base_convert($i,10,5); $n5_str = strval($n5); $tr = array(); $found = 0; for ($j=0; $j<strlen($n5_str); $j+=1) { $k = $n5_str[$j]; if ($k==0) { $found = 1; break; } array_push($tr,$k); } if ($found==1) continue; } else { $tr = array(); } } Can it be done easily in Java?

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• Help dealing with data dependency between two registration forms

  - by franko75

  I have a tricky issue here with a registration of both a user and his/her pet. Both the user and the pet are treated as separate entities and both require separate registration forms. However, the user's pet has to be linked to the user via a foreign key in the database. The process is basically that when a new user joins the site, firstly they register their pet, then they register themselves. The reason for this order is to check their pet's eligibility for the site (there are some criteria to be met) first, instead of getting the user to sign up only to then find out their pet is ineligible. It is this ordering of the form submissions which is causing me a bit of a headache, as follows... The site is being developed with an MVC framework, and the User registration process is managed via a method in a User_form controller, while the pet registration process is managed via a method in the Pet_form controller. The pet registration form happens first, and the pet data can be saved without the owner_id at this stage, with the user id possibly being added (e.g by retrieving pet's id from session) following user registration. However, doing it this way could potentially result in redundant data, where pet records would be created in the database, but if the user doesn't actually register themselves too, then the pets will be ownerless records in the DB. Other option is to serialize the new pet's data at the pet registration stage, don't save it to the DB until the user fills out their registration form. Once the user is created, i can pass serialised data AND the owner_id to a method in the Pet Model which can update the DB. However, I also need to set the newly created $pet to $this-pet which I then access for a sequence of other related forms. Should I just set the session variable in the model method? Then in the Pet controller constructor, do a check for pet stored in session, if yes, assign to $this-pet... If this makes any sense to anybody and you have some advice, i'd be grateful to hear it!

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• Algorithm to determine indices i..j of array A containing all the elements of another array B

  - by Skylark

  I came across this question on an interview questions thread. Here is the question: Given two integer arrays A [1..n] and B[1..m], find the smallest window in A that contains all elements of B. In other words, find a pair < i , j such that A[i..j] contains B[1..m]. If A doesn't contain all the elements of B, then i,j can be returned as -1. The integers in A need not be in the same order as they are in B. If there are more than one smallest window (different, but have the same size), then its enough to return one of them. Example: A[1,2,5,11,2,6,8,24,101,17,8] and B[5,2,11,8,17]. The algorithm should return i = 2 (index of 5 in A) and j = 9 (index of 17 in A). Now I can think of two variations. Let's suppose that B has duplicates. This variation doesn't consider the number of times each element occurs in B. It just checks for all the unique elements that occur in B and finds the smallest corresponding window in A that satisfies the above problem. For example, if A[1,2,4,5,7] and B[2,2,5], this variation doesn't bother about there being two 2's in B and just checks A for the unique integers in B namely 2 and 5 and hence returns i=1, j=3. This variation accounts for duplicates in B. If there are two 2's in B, then it expects to see at least two 2's in A as well. If not, it returns -1,-1. When you answer, please do let me know which variation you are answering. Pseudocode should do. Please mention space and time complexity if it is tricky to calculate it. Mention if your solution assumes array indices to start at 1 or 0 too. Thanks in advance.

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• Javascript Namespace Help

  - by Jason

  Hi, I have a pretty big Javascript script with loads of global variables & functions in it. Then a piece of code that calls one function from this js file: myfunc(); Ok, now I have cloned this script and modified some functionality, all function prototypes and variables are named the same in both scripts. So now I have two scripts loaded and one call to myfunc(), now we have a clash because there are loads of global variables with the same names and two myfunc()s. What I want to do is wrap this cloned script in a namespace, so that I can modify the original call to: clone.myfunc() which will call the new function, but I also want myfunc() to just refer to the original script. In other words I can't touch the original script (no permissions) and I want to be able to use both the clone and the original at runtime. This is the script im cloning: http://pastebin.com/6KR5T3Ah Javascript namespaces seem quite tricky this seems a nice namespace method: var namespace = { foo: function() { } bar: function() { } } ... namespace.foo(); } However that requires using an object, and the script (as posted above) is humongous at nearly 4000 lines, too much to objectize I think? Anyone know a better solution to avoid namespace pollution, with one script I cant touch and one being a clone of that script. Just so I can call myfunc() and clone.myfunc() and all global variables will behave in their respected scope. It's either that, or I go through and modify everything to have unique names, which may take a lifetime This is a Mozilla addon if it helps context wise. Thanks.

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• Multiple/nested "select where" with Zend_Db_Select

  - by DJRayon

  Hi there I need to create something like this: select name from table where active = 1 AND (name LIKE 'bla' OR description LIKE 'bla') The first part is easy: $sqlcmd = $db->select() ->from("table", "name") ->where("active = ?", 1) Now comes the tricky part. How can I nest? I know that I can just write ->orWhere("name LIKE ? OR description LIKE ?", "bla") But thats wron, because I need to dynamically change all the parts. The query will be built all the time the script runs. Some parts get deleted, some altered. In this example I need to add those OR-s because sometimes I need to search wider. "My Zend Logic" tells me that the correct way is like this: $sqlcmd = $db->select() ->from("table", "name") ->where("active = ?", 1) ->where(array( $db->select->where("name LIKE ?", "bla"), $db->select->orWhere("description LIKE ?", "bla") )) But that doesn't work (atleast I dont remember it working). Please. Can someone help me to find a object oriented way for nesting "where"-s

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• Transaction within a Transaction in C#

  - by Rosco

  I'm importing a flat file of invoices into a database using C#. I'm using the TransactionScope to roll back the entire operation if a problem is encountered. It is a tricky input file, in that one row does not necessary equal one record. It also includes linked records. An invoice would have a header line, line items, and then a total line. Some of the invoices will need to be skipped, but I may not know it needs to be skipped until I reach the total line. One strategy is to store the header, line items, and total line in memory, and save everything once the total line is reached. I'm pursuing that now. However, I was wondering if it could be done a different way. Creating a "nested" transaction around the invoice, inserting the header row, and line items, then updating the invoice when the total line is reached. This "nested" transaction would roll back if it is determined the invoice needs to be skipped, but the overall transaction would continue. Is this possible, practical, and how would you set this up?

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• Replacing characters in a non well-formed XML body

  - by ryanprayogo

  In a (Java) code that I'm working on, I sometimes deal with a non well-formed XML (represented as a Java String), such as: <root> <foo> bar & baz < quux </foo> </root> Since this XML will eventually need to be unmarshalled (using JAXB), obviously this XML as is will throw exception upon unmarshalling. What's the best way to replace the & and the < to its character entities? For &, it's as easy as: xml.replaceAll("&", "&amp;") However, for the < symbol, it's a bit tricky since obviously I don't want to replace the < that's used for the XML tag opening 'bracket'. Other than scanning the string and manually replacing < in the XML body with &lt;, what other option can you suggest?

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• Computing, storing, and retrieving values to and from an N-Dimensional matrix

  - by Adam S

  This question is probably quite different from what you are used to reading here - I hope it can provide a fun challenge. Essentially I have an algorithm that uses 5(or more) variables to compute a single value, called outcome. Now I have to implement this algorithm on an embedded device which has no memory limitations, but has very harsh processing constraints. Because of this, I would like to run a calculation engine which computes outcome for, say, 20 different values of each variable and stores this information in a file. You may think of this as a 5(or more)-dimensional matrix or 5(or more)-dimensional array, each dimension being 20 entries long. In any modern language, filling this array is as simple as having 5(or more) nested for loops. The tricky part is that I need to dump these values into a file that can then be placed onto the embedded device so that the device can use it as a lookup table. The questions now, are: What format(s) might be acceptable for storing the data? What programs (MATLAB, C#, etc) might be best suited to compute the data? C# must be used to import the data on the device - is this possible given your answer to #1?

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• AJAX filter MySQL results using checkboxes

  - by keepitnang

  I'm attempting to get to grips with displaying filterable MySQL data within a PHP page based on user checkbox selections. I have a database of domain names and the dates on which these will require renewal as per Nominet DAC information and I can get unfiltered data to display, but filtering results by domain extensions is proving tricky for me to accomplish. I should point out at this stage that I am a serious newcomer to many of the ideas I am trying to learn to work with here, so please be gentle. I have tried following some other articles on here also, but no dice. I have the following so far: HTML <input type="checkbox" class="extensions" name="extensions" value=".co.uk">.co.uk</input> <input type="checkbox" class="extensions" name="extensions" value=".org.uk">.org.uk</input> Script $('.extensions').live('click', function() { var all_boxes = $('.extensions'); var all_boxes_values = []; var i = 0; for (var i; i < all_boxes.length; i++) { if (all_boxes[i].checked) { all_boxes_values.push(all_boxes[i].value) } } var all_boxes_values_clean = all_boxes_values.join(", "); console.log(all_boxes_values_clean); $.get("sql-test.php", {q: all_boxes_values_clean}, function(result) { $("div#output").html(result); } )}); PHP $g = $_GET['q']; $extensionsql=""; $extension=1; if(isset($g)) { $extension=1; $param = "" . str_replace(",", "','", $_GET['q']) . ""; } And that's as far as I have gotten with my limited ability. What I would like to do next is search the column domainName for a string match and return the appropriate results to the user. Something to mimic something like the following but I'm not sure how to achieve it. Any help would be much appreciated: SELECT * FROM `refresh` WHERE `domainName` LIKE '%.co.uk%' AND renewalDate LIKE '%2012-06-30%' ORDER BY `domainName` ASC Thanks

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• How to do this in a smart way

  - by Azzyh

  Hello SO. My websystem im coding with now is integrated from the originally phpBB system. With this i mean when you log on my websystem, you have actually logged into the forum from the login page. Now i came to the "log out" part, and i want to make it smart. Right now its a simply link with logout: <a href="<?php echo BASEDIR; ?>../../ucp.php?mode=logout&sid=<? echo $user->data['session_id']; ?>" style="margin-left: 14px; font-size: 10px;">- Log Out</a> As you see in the link it refers to the forum´s ucp.php?mode=logout, and you need to have the SID variable in it in order to log out right.. anyway.. I want to do this log out part in a smart way, i mean, not so you land on the forum´s "you have now been logged out", i want something maybe like run this page in background when you click, and then it refreshes the current page your on. Or should it be smarter just try to modify the phpbb file ucp.php? I think its hard coded, and not the way I am coding, so thats why i find it abit tricky. Thank you for your answers and examples on how this could be done, in a smart way..

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• Use LINQ, to Sort and Filter items in a List<ReturnItem> collection, based on the values within a Li

  - by Daniel McPherson

  This is tricky to explain. We have a DataTable that contains a user configurable selection of columns, which are not known at compile time. Every column in the DataTable is of type String. We need to convert this DataTable into a strongly typed Collection of "ReturnItem" objects so that we can then sort and filter using LINQ for use in our application. We have made some progress as follows: We started with the basic DataTable. We then process the DataTable, creating a new "ReturnItem" object for each row This "ReturnItem" object has just two properties: ID ( string ) and Columns( List(object) ). The properties collection contains one entry for each column, representing a single DataRow. Each property is made Strongly Typed (int, string, datetime, etc). For example it would add a new "DateTime" object to the "ReturnItem" Columns List containing the value of the "Created" Datatable Column. The result is a List(ReturnItem) that we would then like to be able to Sort and Filter using LINQ based on the value in one of the properties, for example, sort on "Created" date. We have been using the LINQ Dynamic Query Library, which gets us so far, but it doesn't look like the way forward because we are using it over a List Collection of objects. Basically, my question boils down to: How can I use LINQ, to Sort and Filter items in a List(ReturnItem) collection, based on the values within a List(object) property which is part of the ReturnItem class?

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• Is there a design pattern to cut down on code duplication when subclassing Activities in Android?

  - by Daniel Lew

  I've got a common task that I do with some Activities - downloading data then displaying it. I've got the downloading part down pat; it is, of course, a little tricky due to the possibility of the user changing the orientation or cancelling the Activity before the download is complete, but the code is there. There is enough code handling these cases such that I don't want to have to copy/paste it to each Activity I have, so I thought to create an abstract subclass Activity itself such that it handles a single background download which then launches a method which fills the page with data. This all works. The issue is that, due to single inheritance, I am forced to recreate the exact same class for any other type of Activity - for example, I use Activity, ListActivity and MapActivity. To use the same technique for all three requires three duplicate classes, except each extends a different Activity. Is there a design pattern that can cut down on the code duplication? As it stands, I have saved much duplication already, but it pains me to see the exact same code in three classes just so that they each subclass a different type of Activity.

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• How can I pivot these key+values rows into a table of complete entries?

  - by CodexArcanum

  Maybe I demand too much from SQL but I feel like this should be possible. I start with a list of key-value pairs, like this: '0:First, 1:Second, 2:Third, 3:Fourth' etc. I can split this up pretty easily with a two-step parse that gets me a table like: EntryNumber PairNumber Item 0 0 0 1 0 First 2 1 1 3 1 Second etc. Now, in the simple case of splitting the pairs into a pair of columns, it's fairly easy. I'm interested in the more advanced case where I might have multiple values per entry, like: '0:First:Fishing, 1:Second:Camping, 2:Third:Hiking' and such. In that generic case, I'd like to find a way to take my 3-column result table and somehow pivot it to have one row per entry and one column per value-part. So I want to turn this: EntryNumber PairNumber Item 0 0 0 1 0 First 2 0 Fishing 3 1 1 4 1 Second 5 1 Camping Into this: Entry [1] [2] [3] 0 0 First Fishing 1 1 Second Camping Is that just too much for SQL to handle, or is there a way? Pivots (even tricky dynamic pivots) seem like an answer, but I can't figure how to get that to work.

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