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• How does one gets started with Winforms style applications on Win32?

  - by Billy ONeal

  EDIT: I'm extremely tired and frustrated at the moment -- please ignore that bit in this question -- I'll edit it in the morning to be better. Okay -- a bit of background: I'm a C++ programmer mostly, but the only GUI stuff I've ever done was on top of .NET's WinForms platform. I'm completely new to Windows GUI programming, and despite Petzold's excellent book, I'm extremely confused. Namely, it seems that most every reference on getting started with Win32 is all about drawing lines and curves and things -- a topic about which (at least at present time) I couldn't care less. I need a checked list box, a splitter, and a textbox -- something that would take less than 10 minutes to do in Winforms land. It has been recommended to me to use the WTL library, which provides an implementation of all three of these controls -- but I keep getting hung up on simple things, such as getting the damn controls to use the right font, and getting High DPI working correctly. I've spent two freaking days on this, and I can't help but think there has to be a better reference for these kinds of things than I've been able to find. Petzold's book is good, but it hasn't been updated since Windows 95 days, and there's been a LOT changed w.r.t. how applications should be correctly developed since it was published. I guess what I'm looking for is a modern Petzold book. Where can I find such a resource, if any?

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• Is it a good idea to use MySQL and Neo4j together?

  - by Sanoj

  I will make an application with a lot of similar items (millions), and I would like to store them in a MySQL database, because I would like to do a lot of statistics and search on specific values for specific columns. But at the same time, I will store relations between all the items, that are related in many connected binary-tree-like structures (transitive closure), and relation databases are not good at that kind of structures, so I would like to store all relations in Neo4j which have good performance for this kind of data. My plan is to have all data except the relations in the MySQL database and all relations with item_id stored in the Neo4j database. When I want to lookup a tree, I first search the Neo4j for all the item_id:s in the tree, then I search the MySQL-database for all the specified items in a query that would look like: SELECT * FROM items WHERE item_id = 45 OR item_id = 345435 OR item_id = 343 OR item_id = 78 OR item_id = 4522 OR item_id = 676 OR item_id = 443 OR item_id = 4255 OR item_id = 4345 Is this a good idea, or am I very wrong? I haven't used graph-databases before. Are there any better approaches to my problem? How would the MySQL-query perform in this case?

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• Implement a threading to prevent UI block on a bug in an async function

  - by Marcx

  I think I ran up againt a bug in an async function... Precisely the getDirectoryListingAsync() of the File class... This method is supposted to return an object containing the lists of files in a specified folder. I found that calling this method on a direcory with a lot of files (in my tests more than 20k files), after few seconds there is a block on the UI until the process is completed... I think that this method is separated in two main block: 1) get the list of files 2) create the array with the details of the files The point 1 seems to be async (for a few second the ui is responsive), then when the process pass from point 1 to point 2 the block of the UI occurs until the complete event is dispathed... Here's some (simple) code: private function checkFiles(dir:File):void { if (dir.exists) { dir.addEventListener( FileListEvent.DIRECTORY_LISTING, listaImmaginiLocale); dir.getDirectoryListingAsync(); // after this point, for the firsts seconds the UI respond well (point 1), // few seconds later (point 2) the UI is frozen } } private function listaImmaginiLocale( event:FileListEvent ):void { // from this point on the UI is responsive again... } Actually in my projects there are some function that perform an heavy cpu usage and to prevent the UI block I implemented a simple function that after some iteration will wait giving time to UI to be refreshed. private var maxIteration:int = 150000; private function sampleFunct(offset:int = 0) :void { if (offset < maxIteration) { // do something // call the recursive function using a timeout.. // if the offset in multiple by 1000 the function will wait 15 millisec, // otherwise it will be called immediately // 1000 is a random number for the pourpose of this example, but I usually change the // value based on how much heavy is the function itself... setTimeout(function():void{aaa(++offset);}, (offset%1000?15:0)); } } Using this method I got a good responsive UI without afflicting performance... I'd like to implement it into the getDirectoryListingAsync method but I don't know if it's possibile how can I do it where is the file to edit or extend.. Any suggestion???

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• iphone - grouping UIImageViews x blocking elements

  - by Mike

  I have to rotate several UIImageViews around a specific center. To accomplish this I am using the famous trick of putting these views as subviews of a larger one and rotating that one. The problem is that these subviews have to detect touches, because each one has buttons on it. The hierarchy is like this LARGE_VIEW | |_____ imageView1 | |_________ button1 | |_________ button2 | |_________ button3 | |_____ imageView2 |_________ button4 |_________ button5 |_________ button6 etc So, to make buttons respond to tap, I had to make this; [LARGE_VIEW setUserInteractionEnabled:YES]; [imageView1 setUserInteractionEnabled:YES]; [imageView2 setUserInteractionEnabled:YES]; ImageView1 and 2 are two vertical rows of buttons on each side of the screen. The problem is that there's another view below LARGE_VIEW and this view is not receiving the taps, because LARGE_VIEW is intercepting them first. I don't need LARGE_VIEW to detect any taps except on the two areas where imageView 1 and 2 are. LARGE_VIEW must let pass taps on the area defined by this rect (52, 0, 768-2*52, 1024). ImageView1 and 2 have this size: 52 pixels wide and 1024 pixels high (iPad). ImageView1's rect is: (0, 0, 52, 1024) and ImageView2's rect is: (768-52, 0, 52, 1024) LARGE_VIEW must let pass taps on the area defined by this rect (52, 0, 768-2*52, 1024). How to solve that? I need LARGE_VIEW detect taps on each rect defined on my previous paragraph and pass these taps to its subviews and just let pass taps outside these rects to the app, so other views BELOW, can detect taps too. thanks.

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• ASP.Net MVC DotNetOpenAuth Sample Issue on publish

  - by Roger D. Pharr

  I'm trying to use the MSDN Open ID project template for ASP.NET MVC C#. I've been able to configure a local copy to run well. But when I publish it to my hosting provider - it craps out. The error is "500 internal server error". Is there something I should know about publishing this template that I haven't noticed? Here are some more details (for diligence): Hosting provider is GoDaddy/SQL2005/IIS7. When I configure & publish the blank MVC template, it works. The local database publishes successfully, but I haven't been able to troubleshoot the connection in web.config yet. I expect there are connection string problems in the file. I tried disabling all of the references to log4net, as it seemed to be invoked several times on startup. But those changes did not seem to make a difference in either the local or published application performance. My IDE is Visual Studio 2010 Pro Any help would be greatly appreciated!

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• Thread-safety of read-only memory access

  - by Edmund

  I've implemented the Barnes-Hut gravity algorithm in C as follows: Build a tree of clustered stars. For each star, traverse the tree and apply the gravitational forces from each applicable node. Update the star velocities and positions. Stage 2 is the most expensive stage, and so is implemented in parallel by dividing the set of stars. E.g. with 1000 stars and 2 threads, I have one thread processing the first 500 stars and the second thread processing the second 500. In practice this works: it speeds the computation by about 30% with two threads on a two-core machine, compared to the non-threaded version. Additionally, it yields the same numerical results as the original non-threaded version. My concern is that the two threads are accessing the same resource (namely, the tree) simultaneously. I have not added any synchronisation to the thread workers, so it's likely they will attempt to read from the same location at some point. Although access to the tree is strictly read-only I am not 100% sure it's safe. It has worked when I've tested it but I know this is no guarantee of correctness! Questions Do I need to make a private copy of the tree for each thread? Even if it is safe, are there performance problems of accessing the same memory from multiple threads?

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• New desktop GUI developer; can choose any platform...

  - by alexantd

  I'm planning a client-server product for a tiny, low-volume, high-cost vertical market. One of the components of the product will be a desktop application, simple to moderate in complexity, for data entry and uploading to a central server from remote PCs and/or Macs via SOAP. The server is a Java web app. Customers will be choosing their platform (Windows or Mac) based on what the client app runs on, so my options are wide-open here. However, I will be developing on a Mac and have a strong allergy to MS-specific technologies (sorry). The app will not need to run on any non-desktop-computer devices and I have total freedom to say it will support X but not Y or Z without any negative consequences (quite the luxury, to be sure). I have a lot of experience in server-side development but very little in desktop GUI stuff, and am evaluating my options on the client - basically what do I want to commit to learning over the next 6+ months. I have server-side Java experience as well as a brief dabble in iPhone development, which went OK. Overall I'm looking for: Ease of learning & development IDE support Healthy surrounding ecosystem (libraries, tools, help, etc.) Quality documentation My options as I see them, in rough order of how I'm currently mentally ranking them: Java Swing Cocoa Java SWT JavaFX Adobe AIR XULRunner Am I leaving anything out?

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• What's a good way to provide additional decoration/metadata for Python function parameters?

  - by Will Dean

  We're considering using Python (IronPython, but I don't think that's relevant) to provide a sort of 'macro' support for another application, which controls a piece of equipment. We'd like to write fairly simple functions in Python, which take a few arguments - these would be things like times and temperatures and positions. Different functions would take different arguments, and the main application would contain user interface (something like a property grid) which allows the users to provide values for the Python function arguments. So, for example function1 might take a time and a temperature, and function2 might take a position and a couple of times. We'd like to be able to dynamically build the user interface from the Python code. Things which are easy to do are to find a list of functions in a module, and (using inspect.getargspec) to get a list of arguments to each function. However, just a list of argument names is not really enough - ideally we'd like to be able to include some more information about each argument - for instance, it's 'type' (high-level type - time, temperature, etc, not language-level type), and perhaps a 'friendly name' or description. So, the question is, what are good 'pythonic' ways of adding this sort of information to a function. The two possibilities I have thought of are: Use a strict naming convention for arguments, and then infer stuff about them from their names (fetched using getargspec) Invent our own docstring meta-language (could be little more than CSV) and use the docstring for our metadata. Because Python seems pretty popular for building scripting into large apps, I imagine this is a solved problem with some common conventions, but I haven't been able to find them.

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• customer.name joining transactions.name vs. customer.id [serial] joining transactions.id [integer]

  - by Frank Computer

  INFORMIX-SQL 7.32 Pawnshop Application: one-to-many relationship where each customer (master) can have many transactions (detail). customer( id serial, pk_name char(30), {PATERNAL-NAME MATERNAL-NAME, FIRST-NAME MIDDLE-NAME} [...] ); unique index on id; unique cluster index on name; transaction( fk_name char(30), ticket_number serial, [...] ); dups cluster index on fk_name; unique index on ticket_number; Several people have told me this is not the correct way to join master to detail. They said I should always join customer.id[serial] to transactions.id[integer]. When a customer pawns merchandise, clerk queries the master using wildcards on name. The query usually returns several customers, clerk scrolls until locating the right name, enters a 'D' to change to detail transactions table, all transactions are automatically queried, then clerk enters an 'A' to add a new transaction. The problem with using customer.id joining transaction.id is that although the customer table is maintained in sorted name order, clustering the transaction table by fk_id groups the transactions by fk_id, but they are not in the same order as the customer name, so when clerk is scrolling through customer names in the master, the system has to jump allover the place to locate the clustered transactions belonging to each customer. As each new customer is added, the next id is assigned to that customer, but new customers dont show up in alphabetical order. I experimented using id joins and confirmed the decrease in performance. How can I use id joins instead of name joins and still preserve the clustered transaction order by name if transactions has no name column?

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• Help regarding database and logic layer for my ASP.NET MVC application

  - by Ismail S

  I'm going to start a new project which is going to be small initially but may grow to big over the years. I'm strongly convinced that I'm going to use ASP.NET MVC with jQuery for UI. I want to go for MySQL as database for some reasons but worried on few things. I've a good years of experience working on SQL Server databases and on one project I've had a bad experience creating and managing stored procedures on MySQL database. I'm totally new to Linq but I see that it is easier to use once you are familiar with it. First thing is that accessing data should be easy. So I thought I should use MySQL to Linq but somewhere I read that it is not directly supported but MySQL .NET connector adds support for EntityFramework. I don't know what are the pros and cons of it. I would love if I can implement repository pattern. Will it be possible if I use Entity Framework? I'm not clear on how I should go about all this or I should just forget every thing and directly use SQL to Linq on SQL Server. I'm also concerned about the performance. Someone told me that if we use Entity framework it fetches lot of data and then filter it. Is that right?

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• Why does the '#weight' property sometimes not have any effect in Drupal forms?

  - by Adrian

  Hello, I'm trying to create a node form for a custom type. I have organic groups and taxonomy both enabled, but want their elements to come out in a non-standard order. So I've implemented hook_form_alter and set the #weight property of the og_nodeapi subarray to -1000, but it still goes after taxonomy and menu. I even tried changing the subarray to a fieldset (to force it to actually be rendered), but no dice. I also tried setting $form['taxonomy']['#weight'] = 1000 (I have two vocabs so it's already being rendered as a fieldset) but that didn't work either. I set the weight of my module very high and confirmed in the system table that it is indeed the highest module on the site - so I'm all out of ideas. Any suggestions? Update: While I'm not exactly sure how, I did manage to get the taxonomy fieldset to sink below everything else, but now I have a related problem that's hopefully more manageable to understand. Within the taxonomy fieldset, I have two items (a tags and a multi-select), and I wanted to add some instructions in hook_form_alter as follows: $form['taxonomy']['instructions'] = array( '#value' => "These are the instructions", '#weight' => -1, ); You guessed it, this appears after the terms inserted by the taxonomy module. However, if I change this to a fieldset: $form['taxonomy']['instructions'] = array( '#type' => 'fieldset', // <-- here '#title' => 'Instructions', // <-- and here for good measure '#value' => "These are the instructions", '#weight' => -1, ); then it magically floats to the top as I'd intended. I also tried textarea (this also worked) and explicitly saying markup (this did not). So basically, changing the type from "markup" (the default IIRC) to "fieldset" has the effect of no longer ignoring its weight.

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• Is this 2D array initialization a bad idea?

  - by Brendan Long

  I have something I need a 2D array for, but for better cache performance, I'd rather have it actually be a normal array. Here's the idea I had but I don't know if it's a terrible idea: const int XWIDTH = 10, YWIDTH = 10; int main(){ int * tempInts = new int[XWIDTH * YWIDTH]; int ** ints = new int*[XWIDTH]; for(int i=0; i<XWIDTH; i++){ ints[i] = &tempInts[i*YWIDTH]; } // do things with ints delete[] ints[0]; delete[] ints; return 0; } So the idea is that instead of newing a bunch of arrays (and having them placed in different places in memory), I just point to an array I made all at once. The reason for the delete[] (int*) ints; is because I'm actually doing this in a class and it would save [trivial amounts of] memory to not save the original pointer. Just wondering if there's any reasons this is a horrible idea. Or if there's an easier/better way. The goal is to be able to access the array as ints[x][y] rather than ints[x*YWIDTH+y].

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• Data structure to build and lookup set of integer ranges

  - by actual

  I have a set of uint32 integers, there may be millions of items in the set. 50-70% of them are consecutive, but in input stream they appear in unpredictable order. I need to: Compress this set into ranges to achieve space efficient representation. Already implemented this using trivial algorithm, since ranges computed only once speed is not important here. After this transformation number of resulting ranges is typically within 5 000-10 000, many of them are single-item, of course. Test membership of some integer, information about specific range in the set is not required. This one must be very fast -- O(1). Was thinking about minimal perfect hash functions, but they do not play well with ranges. Bitsets are very space inefficient. Other structures, like binary trees, has complexity of O(log n), worst thing with them that implementation make many conditional jumps and processor can not predict them well giving poor performance. Is there any data structure or algorithm specialized in integer ranges to solve this task?

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• Advanced search engine or server for relational database [closed]

  - by Pawel

  In my current project we are storing big volume of data in relational database. One of the recent key requirements is to enrich application by adding some advanced search capabilities. In the Project, performance is one of the important factors due to very large tables (10+ milions of records) with parent-children relations (for example: multi-level parent-child relationship, where I am looking for all parents with specific children). The search engine should also be able to check these references for hits. I have found some potential engines on stack overflow, however it looks like that all of them are dedicated rather for text search than relational db and hosted on linux os: lucene Solr Sphinx As I understand some of them use documents as a source of searching, but is it possible or efficient to create programmaticaly documents based on my relational data? As I am not familiar with all of their features/capabilities can anyone please make some recommendations or propose some different solution? To summarize my requirements: framework/engine to search relational database including decendants. support for Microsoft SQL Server can be used in .NET applications preferably hosted on Windows systems Does any of mentioned above are able to solve my problem? do you know any better solution?

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• Java "Pool" of longs or Oracle sequence with reusable values

  - by Anthony Accioly

  Several months ago I implemented a solution to choose unique values from a range between 1 and 65535 (16 bits). This range is used to generate unique Route Targets suffixes, which for this customer massive network (it's a huge ISP) are a very disputed resource, so any free index needs to become immediately available to the end user. To tackle this requirement I used a BitSet. Allocate on the RT index with set and deallocate a suffix with clear. The method nextClearBit() can find the next available index. I handle synchronization / concurrency issues manually. This works pretty well for a small range... The entire index is small (around 10k), it is blazing fast and can be easy serialized into a Blob field. The problem is, some new devices can handle RTs of 32 bits (range 1 / 4294967296). Which can't be managed with a BitSet (it would, by itself, consume around 600Mb, plus be limited to int range). Even with this massive range available, the client still wants to free available Route Targets for the end user, mainly because the lowest ones (up to 65535) - which are compatible with old routers - are being heavily disputed. Before I tell the customer that this is impossible and he will have to conform with my reusable index for lower RTs (up to 65550) and use a database sequence for the other ones (which means that when the user frees a Route Target, it will not become available again). Would anyone shed some light? Maybe some kind soul already implemented a high performance number pool for Java (6 if it matters), or I am missing a killer feature of Oracle database (11R2 if it matters)... Wishful thinking. Thank you very much in advance.

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• Calculating collision for a moving circle, without overlapping the boundaries

  - by Robert Vella

  Let's say I have circle bouncing around inside a rectangular area. At some point this circle will collide with one of the surfaces of the rectangle and reflect back. The usual way I'd do this would be to let the circle overlap that boundary and then reflect the velocity vector. The fact that the circle actually overlaps the boundary isn't usually a problem, nor really noticeable at low velocity. At high velocity it becomes quite clear that the circle is doing something it shouldn't. What I'd like to do is to programmatically take reflection into account and place the circle at it's proper position before displaying it on the screen. This means that I have to calculate the point where it hits the boundary between it's current position and it's future position -- rather than calculating it's new position and then checking if it has hit the boundary. This is a little bit more complicated than the usual circle/rectangle collision problem. I have a vague idea of how I should do it -- basically create a bounding rectangle between the current position and the new position, which brings up a slew of problems of it's own (Since the rectangle is rotated according to the direction of the circle's velocity). However, I'm thinking that this is a common problem, and that a common solution already exists. Is there a common solution to this kind of problem? Perhaps some basic theories which I should look into?

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• How to access a web service behind a NAT?

  - by jr

  We have a product we are deploying to some small businesses. It is basically a RESTful API over SSL using Tomcat. This is installed on the server in the small business and is accessed via an iPhone or other device portable device. So, the devices connecting to the server could come from any number of IP addresses. The problem comes with the installation. When we install this service, it seems to always become a problem when doing port forwarding so the outside world can gain access to tomcat. It seems most time the owner doesn't know router password, etc, etc. I am trying to research other ways we can accomplish this. I've come up with the following and would like to hear other thoughts on the topic. Setup a SSH tunnel from each client office to a central server. Basically the remote devices would connect to that central server on a port and that traffic would be tunneled back to Tomcat in the office. Seems kind of redundant to have SSH and then SSL, but really no other way to accomplish it since end-to-end I need SSL (from device to office). Not sure of performance implications here, but I know it would work. Would need to monitor the tunnel and bring it back up if it goes done, would need to handle SSH key exchanges, etc. Setup uPNP to try and configure the hole for me. Would likely work most of the time, but uPNP isn't guaranteed to be turned on. May be a good next step. Come up with some type of NAT transversal scheme. I'm just not familiar with these and uncertain of how they exactly work. We have access to a centralized server which is required for the authentication if that makes it any easier. What else should I be looking at to get this accomplished?

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• IIS7 dynamic content compression and webservices

  - by vandalo

  I am moving and old asmx webservice to a new server with IIS7. This webservice basically sends a big dataset (10mb+) to a winform application. The old solution was implemented using a custom soap extension which compressed the content before sending the stream to the client. The client, of course, implemented the same custom soap extension, to decompressed the stream in a dataset. Everything has worked pretty well for years. My customer doesn't want to change the code upgrading to WCF. They just want to put the old App on the new server and use the new dynamic content compression features. We're testing things on a test server (win serv 2008) and it seems that it's working pretty well, even if it seems slow: we can't see any difference in performance (speed) between the uncompressed and compressed stream. Here's the question. Where should I put the settings? Most people say I can't put it in my web.config; others say it can be put there. I am a bit confused. Are there any tricks or things I should know? What about mimeTypes? Should I set some parameters, somewhere? ... considering my stream is XML (dataset) ?? Thanks to everyone who would like to help Alberto

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• how to minimize application downtime when updating database and application ORM

  - by yamspog

  We currently run an ecommerce solution for a leisure and travel company. Everytime we have a release, we must bring the ecommerce site down as we update database schema and the data access code. We are using a custom built ORM where each data entity is responsible for their own CRUD operations. This is accomplished by dynamically generating the SQL based on attributes in the data entity. For example, the data entity for an address would be... [tableName="address"] public class address : dataEntity { [column="address1"] public string address1; [column="city"] public string city; } So, if we add a new column to the database, we must update the schema of the database and also update the data entity. As you can expect, the business people are not too happy about this outage as it puts a crimp in their cash-flow. The operations people are not happy as they have to deal with a high-pressure time when database and applications are upgraded. The programmers are upset as they are constantly getting in trouble for the legacy system that they inherited. Do any of you smart people out there have some suggestions?

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• Android opengl releasing textures

  - by user1642418

  I have a bit of a problem. I am developing a game for android + engine and I got stuck. I am getting OpenGL out of memory error and either app crashes or phone hangs after loading a scene multiple times. For example: app launches, shows main menu, 1st level/scene is loaded. Then I go back to main menu, and repeat. It doesnt matter which scene I load, after 4-6 times the error occurs. Some background: Each time when scene is loaded all the resources are released and upon first frame render - needed stuff gets loaded. The performance is more or less ok. Note that I am calling glDeleteTexture method, but I think its not doing its job and releasing memory. Thing is that -when I minimize and open it again - problem doesn't occur, but almost the same things are executed. Problem doesn't occur. This way android releases memory. How do I release/get rid of unused textures properly? This happens on HTC Desire HD ( ice cream sandwich 4.0.4) . Other games works fine, so I bet this is not the problem in ROM.

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• return Queryable<T> or List<T> in a Repository<T>

  - by Danny Chen

  Currently I'm building an windows application using sqlite. In the data base there is a table say User, and in my code there is a Repository<User> and a UserManager. I think it's a very common design. In the repository there is a List method: //Repository<User> class public List<User> List(where, orderby, topN parameters and etc) { //query and return } This brings a problem, if I want to do something complex in UserManager.cs: //UserManager.cs public List<User> ListUsersWithBankAccounts() { var userRep = new UserRepository(); var bankRep = new BankAccountRepository(); var result = //do something complex, say "I want the users live in NY //and have at least two bank accounts in the system } You can see, returning List<User> brings performance issue, becuase the query is executed earlier than expected. Now I need to change it to something like a IQueryable<T>: //Repository<User> class public TableQuery<User> List(where, orderby, topN parameters and etc) { //query and return } TableQuery<T> is part of the sqlite driver, which is almost equals to IQueryable<T> in EF, which provides a query and won't execute it immediately. But now the problem is: in UserManager.cs, it doesn't know what is a TableQuery<T>, I need to add new reference and import namespaces like using SQLite.Query in the business layer project. It really brings bad code feeling. Why should my business layer know the details of the database? why should the business layer know what's SQLite? What's the correct design then?

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• Approaches for animating a C# property over time?

  - by Mario Fritsch

  I'm currently trying to animate a bunch of public properties on certain objects. Usually they are of type float or vectors of floats (the type is known at compile-time). I want to be able to: assign a static value to them (MyObject.Duration = 10f;) or assign a random value to them by specifying a minimum and maximum value and optionally also a weight (MyObject.Duration = new RandomFloat(5f, 20f, 2f);) or "bind" this property to the property of another object (think of a child object binding some of its properties to its parent object, like its color or size or sth.) or assign sort of a keyframe animation to them, specifying a variable number of keyframes with timecode and the property's value at that specific point in time as well as information about how to interpolate between these frames The keyframes should be able to accept random values for each frame, both for the time and the property's value. What would be a practical approach for this kind of system? Currently I'm thinking about polymorphism: implement a base class or interface with a public Value-property and/or GetValue(float time)-method and then creating different sub classes like StaticValue, RandomValue, BindingValue and AnimatedValue implementing this base class or interface. Doesn't seem very elegant, though, and the initialization of even simple objects becomes a bit tedious. Another idea would be to implement these properties just as regular floats or vectors and create special "Modifier"-types binding to these properties. To retrieve the "real" value of the property, I'd first call any Modifier bound to the property, which would in turn update the actual object's property for me to retrieve later on. That would most likely mean using reflection at some point, which could be quite bad for performance as I'll probably have thousands of properties to update dozens of times per second. Any suggestions on this? Being a novice I'm (hopefully) missing some far more elegant and/or practical solution than I'm already playing around with :( Edit: Probably should have mentioned this earlier, but WPF isn't an option - it's not available on all targetted platforms, so I can't rely on it. I'm aware of its powerful databinding and animation capabilities, but I need to roll my own (or find some other lightweight alternative meeting my needs).

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• MySQL 5.5.8 Gets Periodic Lag

  - by CYREX

  Am using MySQL 5.5.8 on an Ubuntu system and every X amount of time it creates a huge lag that lasts a couple of seconds. Then all goes back to normal until the next lag. The time period varies but it looks like it happen periodically. Am using InnoDB. It is like hiccups in the MySQL. What could be creating this sort of periodic problem. Do not have any cron jobs or process running every time the X period happens. The X period could be between 30 minutes to 2 hours. So for example it could happen every 30 minutes for the next 12 hours or it could happen every 2 hours for the next 8 hours. key_buffer_size = 256M max_allowed_packet = 1M table_cache = 1024 table_open_cache = 1024 sort_buffer_size = 2M read_buffer_size = 2M read_rnd_buffer_size = 4M myisam_sort_buffer_size = 32M thread_cache_size = 128 query_cache_size= 128M log-slow-queries = slow.log long_query_time = 5 log-queries-not-using-indexes # Try number of CPU's*2 for thread_concurrency thread_concurrency = 4 max_connections=512 #innodb_data_file_path = ibdata1:10M:autoextend #innodb_log_group_home_dir = /usr/local/mysql/data # You can set .._buffer_pool_size up to 50 - 80 % # of RAM but beware of setting memory usage too high innodb_buffer_pool_size = 1G #innodb_additional_mem_pool_size = 20M # Set .._log_file_size to 25 % of buffer pool size #innodb_log_file_size = 64M #innodb_log_buffer_size = 8M #innodb_flush_log_at_trx_commit = 0 #innodb_lock_wait_timeout = 50 [mysqldump] quick max_allowed_packet = 16M [myisamchk] key_buffer_size = 64M sort_buffer_size = 64M read_buffer = 2M write_buffer = 2M There are about 200+ tables divided in 3 databases. The most written too is in InnoDB. The other ones are more read. Several of the tables in the InnoDB have more than 2 million records. The other databases top at about 400 thousand records and do not change so often. The PC is a Core 2 Duo 8400 with 4GB RAM, 32Bit Ubuntu.

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• WPF Binding to variable / DependencyProperty

  - by Peter

  I'm playing around with WPF Binding and variables. Apparently one can only bind DependencyProperties. I have come up with the following, which works perfectly fine: The code-behind file: public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); } public string Test { get { return (string)this.GetValue(TestProperty); } set { this.SetValue(TestProperty, value); } //set { this.SetValue(TestProperty, "BBB"); } } public static readonly DependencyProperty TestProperty = DependencyProperty.Register( "Test", typeof(string), typeof(MainWindow), new PropertyMetadata("CCC")); private void button1_Click(object sender, RoutedEventArgs e) { MessageBox.Show(Test); Test = "AAA"; MessageBox.Show(Test); } } XAML: <Window x:Class="WpfApplication3.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:diag="clr-namespace:System.Diagnostics;assembly=WindowsBase" Title="MainWindow" Height="350" Width="525" DataContext="{Binding RelativeSource={RelativeSource Self}}"> <Grid> <TextBox Height="31" HorizontalAlignment="Left" Margin="84,86,0,0" Name="textBox1" VerticalAlignment="Top" Width="152" Text="{Binding Test, Mode=TwoWay, diag:PresentationTraceSources.TraceLevel=High}"/> <Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="320,85,0,0" Name="button1" VerticalAlignment="Top" Width="75" Click="button1_Click" /> <TextBox Height="31" HorizontalAlignment="Left" Margin="84,138,0,0" Name="textBox2" Text="{Binding Test, Mode=TwoWay}" VerticalAlignment="Top" Width="152" /> </Grid> The two TextBoxes update one an other. And the Button sets them to "AAA". But now I replaced the Setter function with the one that is commented out (simulating some manipulation of the given value). I would expect that whenever the property value is changed it will be reset to "BBB". It does so when you press the button, that is when you set the property in code. But it does for some reason not affect the WPF Bindings, that is you can change the TextBox contents and thus the property, but apparently the Setter is never called. I wonder why that is so, and how one would go about to achive the expected behaviour.

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• Which isolation level should I use for the following insert-if-not-present transaction?

  - by Steve Guidi

  I've written a linq-to-sql program that essentially performs an ETL task, and I've noticed many places where parallelization will improve its performance. However, I'm concerned about preventing uniquness constraint violations when two threads perform the following task (psuedo code). Record CreateRecord(string recordText) { using (MyDataContext database = GetDatabase()) { Record existingRecord = database.MyTable.FirstOrDefault(record.KeyPredicate()); if(existingRecord == null) { existingRecord = CreateRecord(recordText); database.MyTable.InsertOnSubmit(existingRecord); } database.SubmitChanges(); return existingRecord; } } In general, this code executes a SELECT statement to test for record existance, followed by an INSERT statement if the record doesn't exist. It is encapsulated by an implicit transaction. When two threads run this code for the same instance of recordText, I want to prevent them from simultaneously determining that the record doesn't exist, thereby both attempting to create the same record. An isolation level and explicit transaction will work well, except I'm not certain which isolation level I should use -- Serializable should work, but seems too strict. Is there a better choice?

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