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• Cannot implicitly convert type System.Collection.Generic.IEnumberable

  - by Cen

  I'm receiving this error in my Linq statement --- Cannot implicitly convert type 'System.Collections.Generic.IEnumerable' to 'hcgames.ObjectClasses.ShoppingCart.ShoppingCartCartAddon'. An explicit conversion exists (are you missing a cast?) From this query ShoppingCartItems items = Cart.GetAllItems(); ShoppingCartCartAddons addons = Cart.GetAllAddons(); var stuff = from x in items select new ShoppingCartItem() { ProductID = x.ProductID, Quantity = x.Quantity, Name = x.Name, Price = x.Price, Weight = x.Weight, Addons = (from y in addons where y.ShoppingCartItemID == x.ID select y) }; I can not figure out how to cast this properly. Any suggestions? Thanks for your help!

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• One executable with cmd-line params or just many satellite executables?

  - by Nikos Baxevanis

  I design an application back-end. For now, it is a .NET process (a Console Application) which hosts various communication frameworks such as Agatha and NServiceBus. I need to periodically update my datastore with values (coming from the application while it's running). I found three possible ways: Accept command line arguments, so I can call my console app with -update. On start up a background thread will periodically invoke the update method. Create an updater.exe app which will do the updates, but I will have code duplication since in some way it will need to query the data from the source in order to save it to the datastore. Which one is better?

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• javascript: execute a bunch of asynchronous method with one callback

  - by Samuel Michelot

  I need to execute a bunch of asynchronous methods (client SQLite database), and call only one final callback. Of course, the ugly way is: execAll : function(callBack) { asynch1(function() { asynch2(function() { ... asynchN(function() { callBack(); }) }) }); } But I know there are better ways to do it. Intuitively I would detect when all call back has been called with a counter to call the final callback. I think this is a common design-pattern, so if someone could point me in the right direction... Thanks in advance !

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• System::IDisposable woes

  - by shadeMe

  public ref class ScriptEditor : public Form { public: typedef map<UInt32, ScriptEditor^> AlMap; static AlMap AllocationMap; Form^ EditorForm; RichTextBox^ EditorBox; StatusBar^ EditorStatusBar; StatusBarPanel^ StatusBarLineNo; void Destroy() { EditorForm->Close(); } ScriptEditor(unsigned int PosX, unsigned int PosY); }; The above code throws an Error C2039: '{dtor}' : is not a member of 'System::IDisposable'. I'm quite lost after having looked into articles that explain how the CLR manages memory. Any advice on getting rid of it would be appreciated. My first dabble in C+++/CLI isn't going too well.

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• Surrogate key for date dimension?

  - by Navin

  There are 2 school of thoughts : Use surrogate key preferbly in the format of YYYYMMDD as this will always be sequential. Eliminate Date dimension surrogate key and use actual date instead. My Questions to experts on dimension modeling are : 1> Which design would you prefer and why ? 2> How should we handle unknown values in each of the cases, Can we simply place NULL in Fact table for unknown dates as Foreign Key can be NULL (if no why)? 3> If we need to partition fact table on date column ,how would we achieve that in case 1. I am inclined towards using actual date and using NULL to represent UNKNOWN dates in fact table , as date related validation on fact can be done without need to look in to dimension table.

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• Sign Up/Login system for multi-domain/multi-server

  - by David

  I'm thinking about a good solution for implementing a sign up/login system that works across different domains and servers. A working example is Olx (you can register in one domain, and your login will work in the rest of domains). The scenario is that every domain (one per country) has its own database. And there will be 2 servers (for example), each one will have the 50% of the domains (and so the 50% of databases). What would you suggest to start with? Database: MySQL 5.1 Server-side language: PHP 5.3 (I will be using Symfony 1.4, so if someone has some suggestion for this framework, it will be interesting too, although it is optional)

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• MongoDB RSS Feed Entries, Embed the Entries in the Feed Object?

  - by Patrick Klingemann

  I am saving a reference to an RSS Feed in MongoDB, each Feed has an ever growing list of Entries. As I'm designing my schema, I'm concerned about this statement from the MongoDB Schema Design - Embed vs. Reference Documentation: If the amount of data to embed is huge (many megabytes), you may read the limit on size of a single object. This will surely happen if I understand the statement correctly. So the question is, I am correct to assume that I should not embed the Feed Entries within a Feed because I'll eventually reach the limit on size of a single object?

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• How to create skype like message window?

  - by Miraaj

  Hi all, I am just trying to design skype like message window , for this I have taken the NSDrawer element. It contains : a table view on left, menu items on top, text field on right bottom and text view at central portion on right side. Using text view I can play with string being displayed but I cannot draw the line between messages or round rectangle surrounding user name and time stamp. Can anyone suggest me how can I achieve same look and feel for central message view as in skype?? or is there any better control then NSTextView to be used for it?? Thanks, for any suggestion... Miraaj

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• Is there a standard practice for storing default application data?

  - by Rox Wen

  Our application includes a default set of data. The default data includes coefficients and other factors that are unlikely to ever change but still need to be update-able by the user. Currently, the original default data is stored as a populated class within the application. Data updates are stored to an external XML file. This design allows us to include a "reset" feature to restore the original default data. Our rationale for not storing defaults externally [e.g. XML file] was to minimize the risk of being altered. The overall volume of data doesn't warrant a database. Is there a standard practice for storing "default" application data?

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• How to create new account using servlets

  - by Alvin

  I want to know how can I create new account using servlets in post method? I'm currently following MVC design pattern, and I want to know if I pass the required data to register new account from JSP page, then how can I get that data in post method? As request.getParameter() method returning me null. How can I know that post method is calling to create new account? How can I pass all the relevant user information from servlets to model class for registering data to the database table?

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• Web-Cam Video frames to System.Drawing.Bitmap

  - by Hooch

  Hello. I'm using AForge.NET framework to process some data from webcam. My Image processor is working. class WebProc { public void Process(System.Drawing.Bitmap image) { .... } } I know how to send image from HDD. I was thinking about something like that: private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e) { while(!backgroundWorker1.CancellationPending) { Bitmap Frame GetVidoFrameSomeWay(); WebProc.Process(Frame); } } Can you help me with those questions? How to get frame from webcam? How to list all available webcam for user to chose from? How to open Webcam setting window? Is there a way to set frame size to 640x480 o user size?

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• Lackadaisical One-to-One between Char and Byte Streams

  - by Vaibhav Bajpai

  I expected to have a one-to-one correspondence between the character streams and byte streams in terms of how the classes are organized in their hierarchy. FilterReader and FilterWriter (character streams) correspond back to FilterInputStream and FilterOutputStream (byte stream) classes. However I noticed few changes as - BufferedInputStream extends FilterInputStream, but BufferedReader does NOT extend FilterReader. BufferedOutputStream and PrintStream both extend FilterOutputStream, but BufferedWriter and PrintWriter does NOT extend FilterWriter. FilterInputStream and FilterOutputStream are not abstract classes, but FilterReader and FilterWriter are. I am not sure if I am being too paranoid to point out such differences, but was just curious to know if there was design reasoning behind such decision.

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• FileInputStream for a generic file System

  - by Akhil

  I have a file that contains java serialized objects like "Vector". I have stored this file over Hadoop Distributed File System(HDFS). Now I intend to read this file (using method readObject) in one of the map task. I suppose FileInputStream in = new FileInputStream("hdfs/path/to/file"); wont' work as the file is stored over HDFS. So I thought of using org.apache.hadoop.fs.FileSystem class. But Unfortunately it does not have any method that returns FileInputStream. All it has is a method that returns FSDataInputStream but I want a inputstream that can read serialized java objects like vector from a file rather than just primitive data types that FSDataInputStream would do. Please help!

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• creational pattern for instances depending on multiple subclass instances

  - by markusw

  I have a problem, for that I was not able to identify a suitable design pattern. I want to create instances depending on a given type that has been passed to a factory method. What I am doing until now is the following: T create(SuperType x) { if (x instanceof SubType1) { // do some stuff and return a new SubType extends T } else if (x instanceof SubType2) { // do some stuff and return a new SubType extends T } else if ... } else { throw new UnSupportedOperationException("nothing defined for " + x); } } It seems not to be best pratice for me. Has anybody an idea how to solve this in a better way?

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• What is the safest way to subtract two System.Runtime.InteropServices.ComTypes.FILETIME objects

  - by Anindya Chatterjee

  I wonder what is the safest way to subtract two System.Runtime.InteropServices.ComTypes.FILETIME objects? I used the following code but sometimes it gives me ArithmaticOverflow exception due to the negative number in Low 32-bit values. I am not sure enclosing the body with unchecked will serve the purpose or not. Please give me some suggestion on how to do it safely without getting any runtime exception or CS0675 warning message. private static UInt64 SubtractTimes(FILETIME a, FILETIME b) { UInt64 aInt = ((UInt64)(a.dwHighDateTime << 32)) | (UInt32)a.dwLowDateTime; UInt64 bInt = ((UInt64)(b.dwHighDateTime << 32)) | (UInt32)b.dwLowDateTime; return aInt - bInt; }

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• Wait for tasks to get completed in threadpool.

  - by Alien01

  Hello I have created a thread pool in C++ which stores all tasks in a queue. Thread pool start n number of threads which takes tasks from queue , process each task and then delete tasks from queue. Now , I want to wait till all tasks get completed. Checking for empty queue for completion of tasks may not work as , task can be given to each thread and queue can be emptied but still the tasks can in processing mode. I am not getting idea how to wait for all the tasks completion.This is a design problem. Any suggestions?

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• LINQ - Select Statement - The null value cannot be assigned to a member with type System.Int32 which

  - by thiag0

  I am trying to achieve the following... _4S.NJB_Request request = (from r in db.NJB_Requests where r.RequestId == referenceId select r).Take(1).SingleOrDefault(); Getting the following exception... Message: The null value cannot be assigned to a member with type System.Int32 which is a non-nullable value type. StackTrace: at System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult) at System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries) at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) at System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute[S](Expression expression) at System.Linq.Queryable.SingleOrDefault[TSource](IQueryable`1 source) at DAL.SqlDataProvider.MarkNJBPCRequestAsComplete(Int32 referenceId, Int32 processState) I have verified that 'referenceId' does have a value. Anyone know why this would happen in a select statement? Thanks!

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• In java getting different value for TimeZone.getDefault().getID() on different system

  - by Deepak Chaudhry

  I am getting different value for TimeZone.getDefault().getID() on different systems. For example, in case of Indian standard time, On one of the system we are getting "GMT+5:30": while on another we are getting "Asia/Calcutta". We are expected to get "Asia/calcutta" strings on all machines. Why is there an inconsistency for such behavior? Is there any way to get consistent behavior across different systems windows/MAC? What is the best way to get client time zone programmatically using Java?

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• System.Web.HttpException in asp.net mvc 2 on images and javascript files

  - by Rippo

  Hi I am getting the following errors reported by ELMAH on my asp.net mvc 2 site for javascript files, images etc. System.Web.HttpException: The remote host closed the connection I have done some research and it appears that the user/bot is clicking a link on the site before the page has fully loaded. Now this error never occurs on a controller action but always on a file that is on disk. e.g. /Content/CmsImages/logo.png /Content/CmsImages/MemberImages/Photo-001605.jpg /Content/jquery.tickertype.js So this means that all static files are being routed through the mvc pipeline. What options do I have?

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• Is there such a thing as too many tables?

  - by Stacey

  I've been searching stackoverflow for about an hour now and couldn't find any topics related, so I apologize if this is a duplicate question. My inquery is this. Is there a point at which there are too many tables in a database? Even if the structure is well organized, thought out, and perfectly facilitates the design intent? I have a database that is quickly approaching 40 tables - about 10 main ones, and over 30 ancillary tables (junction tables, 'enumeration' tables, etc). Am I just a bad developer - or should I be trying something different? It seems like so many to me, I'm really afraid at how it will impact the performance of the project. I have done a lot of condensing where possible, grouped similar things where possible, etc. The database is built in MS-SQL 2008.

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• Any ideas for developing a Risc Processor friendly string allocator?

  - by Richard Fabian

  I'm working on some tools to enable high throughput data-oriented development, and one thing that I've not got an immediate answer for is how you go about allocating strings quickly. On risc processors you've got another problem of implementation that the CPU doesn't like branching, which is what I'm trying to minimise or avoid. Also, cache coherence is important on most CPUs, so that's gotta be influential in the design too. So, how would you go about reducing the overhead for a generic string allocator? Sometimes it's easier to solve a more explicit problem, so any ideas for string sizes of 5-30?

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• Extracting an interface from .NEt System classes

  - by Thomas

  When using Visual Studio it is easy to extract an interface from a class that I have written myself. I right click on the class and select 'Refactor' then select 'Extract Interface'. Let's assume for a second that I wanted to create a ConfigurationManager wrapper and write some tests around it. A quick way to do that would be to extract an interface from ConfigurationManager by right clicking it, then 'Go To Definition' and then from inside the class select 'Refactor' then select 'Extract Interface'. Then I would simply create my wrapper class, inherit from my newly created interface, and then implement it and I have a great starting point for my wrapper class. However, extracting an interface from any .NET system classes is not possible, probably because it's just meta data about the classes and not the classes themselves (or I am doing it wrong). Is there an easy way to do what I am trying to accomplish? I want to ensure I am not wasting time typing what I don't need to be typing. Thanks

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• View artifacts leaking into the model of MVC

  - by Jono

  In an ASP.NET MVC application (which has very little chance of having its view technology ported to something non-HTML, but whose functional requirements evolve weekly,) how much HTML should ideally be allowed to be directly represented in the Model? I might come across as a design bigot for this, but I regard it as bad practice to allow any view constructs to "leak" into the model in an MVC application (and vice versa). For example, a Model that represents an item you're about to purchase should know nothing about the HTML check box that says "add giftwrap/message", nor should it know about any HTML drop down lists for payment card types. Conversely the View shouldn't be doing work like figuring out button text by translating keys into values (by looking in resource files.)

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• What's going on with my server? High load, lots of idle CPU time, low disk utilization

  - by Jonathan

  I run a web site and send a legitimate opt-in, daily email newsletter to subscribers. Both the web hosting and email sending are done by the same machine. I have about 100,000 subscribers who have opted in to my daily email newsletter. My PHP script did a pretty good job sending mail to all of them until fairly recently, but as the list has grown I can't keep up. When I run top, I have very high load--usually at least 6 or 7, sometimes as high as 15--even though I only have two CPUs. However, when I run sar, my CPU is idle an average of about 30% of the time. So, it seems I'm not CPU bound. When I run iostat, it seems as though I'm not disk bound because my %util for each device is very low (no more than 5%). Given that I don't seem to be CPU bound or disk bound, why is top reporting such high load? Additionally, since I don't seem to be CPU bound or disk bound, why is my email sending script not able to keep up? Here's what I see when running top: top - 11:33:28 up 74 days, 18:49, 2 users, load average: 7.65, 8.79, 8.28 Tasks: 168 total, 5 running, 162 sleeping, 0 stopped, 1 zombie Cpu(s): 38.9%us, 58.6%sy, 0.8%ni, 0.0%id, 0.7%wa, 0.2%hi, 0.8%si, 0.0%st Mem: 3083012k total, 2144436k used, 938576k free, 281136k buffers Swap: 2048248k total, 39164k used, 2009084k free, 1470412k cached Here's what I see when running iostat -mx: avg-cpu: %user %nice %system %iowait %steal %idle 34.80 1.20 55.24 0.37 0.00 8.38 Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await svctm %util sda 0.19 71.70 1.59 29.45 0.02 0.07 5.90 0.55 17.82 1.16 3.59 sda1 0.00 0.00 0.00 0.00 0.00 0.00 7.10 0.00 13.80 13.72 0.00 sda2 0.05 50.45 1.13 24.57 0.01 0.29 24.25 0.35 13.43 1.15 2.97 sda3 0.05 10.17 0.20 2.33 0.01 0.05 43.75 0.05 20.96 2.45 0.62 sda4 0.00 0.00 0.00 0.00 0.00 0.00 2.00 0.00 70.50 70.50 0.00 sda5 0.07 0.22 0.03 0.07 0.00 0.00 32.84 0.08 856.19 8.03 0.08 sda6 0.02 5.45 0.03 0.72 0.00 0.02 67.55 0.02 26.72 5.26 0.39 sda7 0.00 1.56 0.00 0.42 0.00 0.01 38.04 0.00 8.88 5.84 0.24 sda8 0.01 3.84 0.20 1.35 0.00 0.02 28.55 0.05 31.90 4.08 0.63 Here's what I see when running sar: 09:40:02 AM CPU %user %nice %system %iowait %steal %idle 09:50:01 AM all 30.59 1.01 49.80 0.23 0.00 18.37 10:00:08 AM all 31.73 0.92 51.66 0.13 0.00 15.55 10:10:06 AM all 30.43 0.99 48.94 0.26 0.00 19.38 10:20:01 AM all 29.58 1.00 47.76 0.25 0.00 21.42 10:30:01 AM all 29.37 1.02 47.30 0.18 0.00 22.13 10:40:06 AM all 32.50 1.01 52.94 0.16 0.00 13.39 10:50:01 AM all 30.49 1.00 49.59 0.15 0.00 18.77 11:00:01 AM all 29.43 0.99 47.71 0.17 0.00 21.71 11:10:07 AM all 30.26 0.93 49.48 0.83 0.00 18.50 11:20:02 AM all 29.83 0.81 48.51 1.32 0.00 19.52 11:30:06 AM all 31.18 0.88 51.33 1.15 0.00 15.47 Average: all 26.21 1.15 42.62 0.48 0.00 29.54 Here are the top handful of processes listed at the particular time I happened to run top -c: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 8180 mysql 16 0 57448 19m 2948 S 26.6 0.7 4702:26 /usr/sbin/mysqld --basedir=/ --datadir=/var/lib/mysql --user=mysql --pid-file=/var/lib/mysql/bristno.pid --skip-external-locking 26956 brristno 17 0 0 0 0 Z 8.0 0.0 0:00.24 [php] <defunct> 26958 brristno 17 0 94408 43m 37m R 5.0 1.4 0:00.15 /usr/bin/php /home/brristno/public_html/dbv.php 22852 nobody 16 0 9628 2900 1524 S 0.7 0.1 0:00.17 /usr/local/apache/bin/httpd -k start -DSSL 8591 brristno 34 19 96896 13m 6652 S 0.3 0.4 0:29.82 /usr/local/bin/php /home/brristno/bin/mailer.php 1qwqyb6 i0gbor 24469 nobody 16 0 9628 2880 1508 S 0.3 0.1 0:00.08 /usr/local/apache/bin/httpd -k start -DSSL 25495 nobody 15 0 9628 2876 1500 S 0.3 0.1 0:00.06 /usr/local/apache/bin/httpd -k start -DSSL 26149 nobody 15 0 9628 2864 1504 S 0.3 0.1 0:00.04 /usr/local/apache/bin/httpd -k start -DSSL

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• Determine cluster size of file system in Python

  - by Philip Fourie

  I would like to calculate the "size on disk" of a file in Python. Therefore I would like to determine the cluster size of the file system where the file is stored. How do I determine the cluster size in Python? Or another built-in method that calculates the "size on disk" will also work. I looked at os.path.getsize but it returns the file size in bytes, not taking the FS's block size into consideration. I am hoping that this can be done in an OS independent way...

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