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• Linq where clause with multiple conditions and null check

  - by SocialAddict

  I'm trying to check if a date is not null in linq and if it isn't check its a past date. QuestionnaireRepo.FindAll(q => !q.ExpiredDate.HasValue || q.ExpiredDate >DateTime.Now).OrderByDescending(order => order.CreatedDate); I need the second check to only apply if the first is true. I am using a single repository pattern and FindAll accepted a where clause ANy ideas? There are lots of similar questions on here but not that give the answer, I'm very new to Linq as you may of guessed :) Edit: I get the results I require now but it will be checking the conditional on null values in some cases. Is this not a bad thing?

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• Regex to leave desired string remaining and others removed

  - by m7d

  In Ruby, what regex will strip out all but a desired string if present in the containing string? I know about /[^abc]/ for characters, but what about strings? Say I have the string "group=4&type_ids[]=2&type_ids[]=7&saved=1" and want to retain the pattern group=\d, if it is present in the string using only a regex? Currently, I am splitting on & and then doing a select with matching condition =~ /group=\d/ on the resulting enumerable collection. It works fine, but I'd like to know the regex to do this more directly.

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• Inner synchronization on the same object as the outer synchronization

  - by Yaneeve

  Recently I attended a lecture concerning some design patterns: The following code had been displayed: public static Singleton getInstance() { if (instance == null) { synchronized(Singleton.class) { //1 Singleton inst = instance; //2 if (inst == null) { synchronized(Singleton.class) { //3 inst = new Singleton(); //4 } instance = inst; //5 } } } return instance; } taken from: Double-checked locking: Take two My question has nothing to do with the above mentioned pattern but with the synchronized block: Is there any benefit whatsoever to the double synchronization done in lines 1 & 3 with regards to the fact that the synchronize operation is done on the same Object?

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• Jetty 7 + MySQL Config [java.lang.ClassNotFoundException: org.mortbay.jetty.webapp.WebAppContext]

  - by Scott Chang

  I've been trying to get a c3p0 db connection pool configured for Jetty, but I keep getting a ClassNotFoundException: 2010-03-14 19:32:12.028:WARN::Failed startup of context WebAppContext@fccada@fccada/phpMyAdmin,file:/usr/local/jetty/webapps/phpMyAdmin/,file:/usr/local/jetty/webapps/phpMyAdmin/ java.lang.ClassNotFoundException: org.mortbay.jetty.webapp.WebAppContext at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at java.lang.ClassLoader.loadClass(ClassLoader.java:252) at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:313) at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:266) at org.eclipse.jetty.util.Loader.loadClass(Loader.java:90) at org.eclipse.jetty.xml.XmlConfiguration.nodeClass(XmlConfiguration.java:224) at org.eclipse.jetty.xml.XmlConfiguration.configure(XmlConfiguration.java:187) at org.eclipse.jetty.webapp.JettyWebXmlConfiguration.configure(JettyWebXmlConfiguration.java:77) at org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:975) at org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:586) at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:349) at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:55) at org.eclipse.jetty.server.handler.HandlerCollection.doStart(HandlerCollection.java:165) at org.eclipse.jetty.server.handler.ContextHandlerCollection.doStart(ContextHandlerCollection.java:162) at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:55) at org.eclipse.jetty.server.handler.HandlerCollection.doStart(HandlerCollection.java:165) at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:55) at org.eclipse.jetty.server.handler.HandlerWrapper.doStart(HandlerWrapper.java:92) at org.eclipse.jetty.server.Server.doStart(Server.java:228) at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:55) at org.eclipse.jetty.xml.XmlConfiguration$1.run(XmlConfiguration.java:990) at java.security.AccessController.doPrivileged(Native Method) at org.eclipse.jetty.xml.XmlConfiguration.main(XmlConfiguration.java:955) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.eclipse.jetty.start.Main.invokeMain(Main.java:394) at org.eclipse.jetty.start.Main.start(Main.java:546) at org.eclipse.jetty.start.Main.parseCommandLine(Main.java:208) at org.eclipse.jetty.start.Main.main(Main.java:75) I'm new to Jetty and I want to ultimately get phpMyAdmin and WordPress to run on it through Quercus and a JDBC connection. Here are my web.xml and jetty-web.xml files in my WEB-INF directory. jetty-web.xml: <?xml version="1.0"?> <!DOCTYPE Configure PUBLIC "-//Mort Bay Consulting//DTD Configure//EN" "http://jetty.mortbay.org/configure.dtd"> <Configure class="org.mortbay.jetty.webapp.WebAppContext"> <New id="mysql" class="org.mortbay.jetty.plus.naming.Resource"> <Arg>jdbc/mysql</Arg> <Arg> <New class="com.mchange.v2.c3p0.ComboPooledDataSource"> <Set name="Url">jdbc:mysql://localhost:3306/mysql</Set> <Set name="User">user</Set> <Set name="Password">pw</Set> </New> </Arg> </New> </Configure> web.xml: <?xml version="1.0"?> <!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN" "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd"> <web-app> <description>Caucho Technology's PHP Implementation</description> <resource-ref> <description>My DataSource Reference</description> <res-ref-name>jdbc/mysql</res-ref-name> <res-type>javax.sql.DataSource</res-type> <res-auth>Container</res-auth> </resource-ref> <servlet> <servlet-name>Quercus Servlet</servlet-name> <servlet-class>com.caucho.quercus.servlet.QuercusServlet</servlet-class> <!-- Specifies the encoding Quercus should use to read in PHP scripts. --> <init-param> <param-name>script-encoding</param-name> <param-value>UTF-8</param-value> </init-param> <!-- Tells Quercus to use the following JDBC database and to ignore the arguments of mysql_connect(). --> <init-param> <param-name>database</param-name> <param-value>jdbc/mysql</param-value> </init-param> <init-param> <param-name>ini-file</param-name> <param-value>WEB-INF/php.ini</param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>Quercus Servlet</servlet-name> <url-pattern>*.php</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.php</welcome-file> </welcome-file-list> </web-app> I'm guessing that I'm missing a few jars or something. Currently I have placed the following jars in my WEB-INF/lib directory: c3p0-0.9.1.2.jar commons-dbcp-1.4.jar commons-pool-1.5.4.jar mysql-connector-java-5.1.12-bin.jar I have also tried to put these jars in JETTY-HOME/lib/ext, but to no avail... Someone please tell me what is wrong with my configuration. I'm sick of digging through Jetty's crappy documentation.

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• Singleton by Jon Skeet clarification

  - by amutha

  public sealed class Singleton { Singleton() { } public static Singleton Instance { get { return Nested.instance; } } class Nested { // Explicit static constructor to tell C# compiler // not to mark type as beforefieldinit static Nested() { } internal static readonly Singleton instance = new Singleton(); } } I wish to implement Jon Skeet's Singleton pattern in my current application in C#. I have two doubts on the code 1) How is it possible to access the outer class inside nested class? I mean internal static readonly Singleton instance = new Singleton(); Is something called closure? 2) I did not get this comment // Explicit static constructor to tell C# compiler // not to mark type as beforefieldinit what does this comment suggest us?

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• [PHP] Singleton class and using inheritance

  - by Saif Bechan

  I have am working on a web application that makes use of helper classes. These classes hold functions to various operation such as form handling. Sometimes I need these classes at more than one spot in my application, The way I do it now is to make a new Object. I can't pass the variable, this will be too much work. I was wondering of using singleton classes for this. This way I am sure only one instance is running at a time. My question however is when I use this pattern, should I make a singleton class for all the objects, this would b a lot of code replication. Could I instead make a super class of superHelper, which is a singleton class, and then let every helper extend it. Would this sort of set up work, or is there another alternative? And if it works, does someone have any suggestions on how to code such a superHelper class. Thank you guys

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• why is there no interface file with silverlight enabled wcf services

  - by Ralph Shillington

  Using Visual Studio 2010 when creating a wcf service the template creates a class file, svc endpoint and an interface file. Why is it that when adding a silverlight-enabled wcf service they don't follow this pattern. As discussed here this seems like a bad idea. After adding the silverlight-enabled service, should one go back and incorporate the interface as discussed in the referenced article. If so, then would it not be as simple to start with a simple WCF service, bypassing the whole "silverlight-enabled" bits altogether.

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• Good examples of MVVM Template

  - by jwarzech

  I am currently working with the Microsoft MVVM template and find the lack of detailed examples frustrating. The included ContactBook example shows very little Command handling and the only other example I've found is from an MSDN Magazine article where the concepts are similar but uses a slightly different approach and still lack in any complexity. Are there any decent MVVM examples that at least show basic CRUD operations and dialog/content switching? Everyone's suggestions were really useful and I will start compiling a list of good resources Frameworks/Templates WPF Model-View-ViewModel Toolkit MVVM Light Toolkit Prism Caliburn Cinch Useful Articles Data Validation in .NET 3.5 Using a ViewModel to Provide Meaningful Validation Error Messages Action based ViewModel and Model validation Dialogs Command Bindings in MVVM More than just MVC for WPF MVVM + Mediator Example Application Additional Libraries WPF Disciples' improved Mediator Pattern implementation(I highly recommend this for applications that have more complex navigation)

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• org.apache.struts2.dispatcher.Dispatcher: Could not find action or result Error

  - by peterwkc

  i tried to code the following simple struts but encounter this error during run time. [org.apache.struts2.dispatcher.Dispatcher] Could not find action or result: No result defined for action com.peter.action.LoginAction and result success index.jsp <%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <%@ taglib prefix="s" uri="/struts-tags" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Struts Tutorial</title> </head> <body> <h2>Hello Struts</h2> <s:form action="login" > <s:textfield name="username" label="Username:" /> <s:password name="password" label="Password:"/> <s:submit /> </s:form> </body> </html> LoginAction.java /** * */ package com.peter.action; //import org.apache.struts2.convention.annotation.Namespace; import org.apache.struts2.convention.annotation.ResultPath; import org.apache.struts2.convention.annotation.Result; import org.apache.struts2.convention.annotation.Action; import com.opensymphony.xwork2.ActionSupport; /** * @author nicholas_tse * */ //@Namespace("/") To define URL namespace @ResultPath("/") // To instruct Struts where to search result page(jsp) public class LoginAction extends ActionSupport { private String username, password; /** * */ private static final long serialVersionUID = -8992836566328180883L; /** * */ public LoginAction() { // TODO Auto-generated constructor stub } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } @Override @Action(value = "login", results = {@Result(name="success", location="welcome.jsp")}) public String execute() { return SUCCESS; } } /* Remove * struts2-gxp-plugin * struts2-portlet-plugin * struts2-jsf-plugin * struts2-osgi-plugin and its related osgi-plugin * struts-rest-plugin * * Add * velocity-tools-view * * */ web.xml <?xml version="1.0" encoding="UTF-8"?> <web-app id="WebApp_ID" version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"> <display-name>Struts</display-name> <!-- org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter org.apache.struts2.dispatcher.FilterDispatcher --> <filter> <filter-name>Struts_Filter</filter-name> <filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class> <init-param> <param-name>actionPackages</param-name> <param-value>com.peter.action</param-value> </init-param> </filter> <filter-mapping> <filter-name>Struts_Filter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app> Besides the runtime error, there is deployment error which is ERROR [com.opensymphony.xwork2.util.finder.ClassFinder] (MSC service thread 1-2) Unable to read class [WEB-INF.classes.com.peter.action.LoginAction]: Could not load WEB-INF/classes/com/peter/action/LoginAction.class - [unknown location] at com.opensymphony.xwork2.util.finder.ClassFinder.readClassDef(ClassFinder.java:785) [xwork-core-2.3.1.2.jar:2.3.1.2] AFAIK, the scanning methodology of struts will scan the default packages named struts2 for any annotated class but i have instructed struts2 to scan in com.peter.action using init-param but still unable to find the class. It is pretty weird. Please help. Thanks.

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• WCF Data Services consuming data from EF based repository

  - by John Kattenhorn

  We have an existing repository which is based on EF4 / POCO and is working well. We want to add a service layer using WCF Data Services and looking for some best practice advice. So far we have developed a class which has a IQueryable property and the getter triggers the repository 'get all users' method. The problem so far have been two-fold: 1) It required us to decorate the ID field of the poco object to tell data service what field was the id. This now means that our POCO object is not 'pure'. 2) It cannot figure out the relationships between the objects (which is obvious i guess). I've now stopped this approach and i'm thinking that maybe we should expose the OBjectContext from the repository and use more 'automatic' functionality of EF. Has anybody got any advice or examples of using the repository pattern with WCF Data Services ?

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• Unix [Homework]: Get a list of /home/user/ directories in /etc/passwd

  - by KChaloux

  I'm very new to Unix, and currently taking a class learning the basics of the system and its commands. I'm looking for a single command line to list off all of the user home directories in alphabetical order from the /etc/passwd directory. This applies only to the home directories, and not the contents within them. There should be no duplicate entries. I've tried many permutations of commands such as the following: sort -d | find /etc/passwd /home/* -type -d | uniq | less I've tried using -path, -name, removing -type, using -prune, and changing the search pattern to things like /home/*/$, but haven't gotten good results once. At best I can get a list of my own directory (complete with every directory inside it, which is bad), and the directories of the other students on the server (without the contained directories, which is good). I just can't get it to display the /home/user directories and nothing else for my own account. Many thanks in advance.

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• MSSQL EXPRESS 2008 Stored Procedure execution time spikes periodically

  - by user156241

  I have a big stored procedure on a MSSQL 2008 Express SP2 database that gets run about every 200 ms. Normal execution time is about 50ms. What I am seeing is large inconsistencies in this run time. It will execute for while, say 50-100 times at 40-60ms which is expected, then seemingly at random the same stored procedure will take way longer, say 900ms or 1.5 seconds to run. Sometimes more than one call of the same procedure in a row will take longer too. It appears that something is causing sql server to slow down dramatically every minute or so, but I can't figure out what. There is no timing pattern between the occurences. I have the same setup on two different computers, one of which is a clean XP Pro load with no virus checking and nothing installed except SQL server. Also, The recovery options for all the databases are set to "Simple".

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• Problem with deploying simple Spring MVC Portlet to Liferay 5.2.3

  - by Johannes Hipp

  Hello, I try to deploy a simple spring portlet in ext (I can't use Plugins SDK...) on Liferay 5.2.3 My portlet: ext-impl/src: package: com.ext.portlet.springmvc HelloWorldController.java [code] package com.ext.portlet.springmvc; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.springframework.web.servlet.ModelAndView; import org.springframework.web.servlet.mvc.Controller; public class HelloWorldController implements Controller { public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String aMessage = "Hello World MVC!"; ModelAndView modelAndView = new ModelAndView("hello_world"); modelAndView.addObject("message", aMessage); return modelAndView; } } [/code] ext-lib: - jstr.jar - spring-webmvc.jar - spring-webmvc-portlet.jar - spring.jar - standard.jar ext-web/docroot/html/portlet/ext/springmvc/hello_world.jsp [code] <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <html> <body> <p>This is my message: ${message}</p> </body> </html> [/code] ext-web/docroot/html/portlet/ext/springmvc/index.jsp [code] <html> <body> <p>Hi</p> </body> </html> [/code] ext-web/docroot/WEB-INF/springmvc-servlet.xml [code] <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"> <bean name="/hello_world.html" class="com.ext.portlet.springmvc.HelloWorldController"/> <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/> <property name="prefix" value="/jsp/"/> <property name="suffix" value=".jsp"/> </bean> </beans> [/code] ext-web/docroot/WEB-INF/portlet-ext.xml [code] <portlet> <portlet-name>springmvc</portlet-name> <portlet-class>org.springframework.web.portlet.DispatcherPortlet</portlet-class> <supports> <mime-type>text/html</mime-type> <portlet-mode>view</portlet-mode> </supports> <portlet-info> <title>Simple JSP Portlet</title> </portlet-info> <security-role-ref> <role-name>power-user</role-name> </security-role-ref> <security-role-ref> <role-name>user</role-name> </security-role-ref> </portlet> [/code] ext-web/docroot/WEB-INF/web.xml [code] <?xml version="1.0"?> <web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4"> <servlet> <servlet-name>springmvc</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>springmvc</servlet-name> <url-pattern>*.html</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file> jsp/index.jsp </welcome-file> </welcome-file-list> </web-app> [/code] Are there some mistakes? I get this error, when I try to deploy: [code] Website OC4J 10g (10.1.3) Default Web Site definiert ist. Error creating bean w ith name 'com.liferay.portal.kernel.captcha.CaptchaUtil' defined in class path r esource [META-INF/util-spring.xml]: Cannot create inner bean 'com.liferay.portal .captcha.CaptchaImpl#1424b7b' of type [com.liferay.portal.captcha.CaptchaImpl] w hile setting bean property 'captcha'; nested exception is org.springframework.be ans.factory.BeanCreationException: Error creating bean with name 'com.liferay.po rtal.captcha.CaptchaImpl#1424b7b' defined in class path resource [META-INF/util- spring.xml]: Instantiation of bean failed; nested exception is org.springframewo rk.beans.BeanInstantiationException: Could not instantiate bean class [com.lifer ay.portal.captcha.CaptchaImpl]: Constructor threw exception; nested exception is java.lang.NullPointerException [/code] Hope anybody can help me... Thank you very much. Best regards, Johannes

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• How are views constructed in Josh Smith's MVVM sample?

  - by Wim Coenen

  Being new to both WPF and MVVM, I'm studying Josh Smith's article on the MVVM pattern and the accompanying sample code. I can see that the application is started in app.xaml.cs by constructing a MainWindow object, wiring it to a MainWindowViewModel object and then showing the main window. So far so good. However, I can't find any code which instantiates the AllCustomersView or CustomerView classes. Using "find all references" on the constructors of those views comes up with nothing. What am I missing here?

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• .NET Build Process

  - by Nix

  All I am looking for the best free set of tools to be used in a MS Based build process. Checkout, Build, Package, Test, Deploy, etc. I know this question has been asked before but it was over 2 years ago, and in our world that is an eternity. I am looking to develop a pattern that is easily adapted to similar projects. Almost like a template/cookie cutter system. I am currently looking into using CruiseControl, Powershell, MSBuild suite of tools. If we choose to move to 4.0 will we have issues? Are there better alternatives? Limitations ? Or will these pretty much meet my needs. One piece that i am never happy with is the process of packaging. We actually have opted in the past to just use Visual Studio Deployment Projects but those are very* ancient and my fear is WIX will be too complicated for the people implementing it.

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• Unexpected result in .NET 4 DirectoryInfo.EnumerateFiles(string)

  - by xkingpin

  It seems that the following code is not working as expected. I would assume that the following call to EnumarateFiles would only return files that match the filename pattern of c* ... however, filenames with H* are still getting returned. For example... the following file will get deleted in the following code (HNNN09060900932.xml). What's the issue? This is a major bug in my application. string searchPattern = "C*"; // get each file in this directory that is less than a given date var files = from file in SubDir.EnumerateFiles(searchPattern) where file.LastWriteTime < KeepDate select file; foreach (var file in files) { file.Delete(); }

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• PerThreadLifetimeManager in Unity

  - by DorianGrey

  Hi, In the Unity PerThreadLifetimeManager documentation, I read that: "This lifetime manager does not dispose the instances it holds". Ref.: http://msdn.microsoft.com/en-us/library/ff647854.aspx So, if I am using a ThreadPool, does it mean that objects resolved using Unity on a Thread of the ThreadPool will not get disposed at the end of the work done in that thread before being returned to the pool? Any pattern or ideas how I can ensure that the objects do get disposed & I get a clean thread from the thread pool? Thanks!

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• Neural Network Output Grouping 0.5?

  - by Mike

  I tried to write a Neural Network system, but even running through simple AND/OR/NOR type problems, the outputs seem to group around 0.5 (for a bias of -1) and 0.7 (for a bias of 1). It doesn't look exactly "wrong"... The 1,1 in the AND pattern does seem higher than the rest and the 0,0 in the OR looks lower, but they are still all grouped so it's debatable. I was wondering a) if there's some obvious mistake I've made or b) if there's any advice for debugging Neural Nets... seeing as you can't always track back exactly where an answer came from... Thanks! Mike

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• Fastest way to convert datatable to generic list

  - by Joel Coehoorn

  I have a data tier select method that returns a datatable. It's called from a business tier method that should then return a strongly typed generic List. What I want to do is very similar (but not the same as) this question: http://stackoverflow.com/questions/208532/how-do-you-convert-a-datatable-into-a-generic-list What's different is that I want the list to contain strongly-typed objects rather than datarows (also, I don't have linq avaiable here yet). I'm concerned about performance. The business tier method will in turn be called from the presentation tier, and the results will be iterated for display to the user. It seems very wasteful to add an extra iteration at the business tier, only do it again right away for the presentation, so I want this to be as quick as possible. This is a common task, so I'm really looking for a good pattern that can be repeated over and over.

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• robocode engine: how to design (write) the runtime engine -- the robot world

  - by Bob

  IBM has (had) a free learn-Java program called RoboCode, in which custom robots could be written that would then do battle in a 2D space. I would like to write the environment that supports such robots, but don't know what pattern or design to use. Each robot is a thread. Each thread is given a certain (indeterminate) amount of run-time by the JRE. A robot world engine would start by building a list of the players/robots, then enter a loop that allows each player in turn to do whatever it likes: move forward, turn left, fire toward the northwest corner, whatever. Each robot is also informed of events of interest: an enemy or several enemies are within range, it has been hit by a bullet, etc. The combination of handling threads that are also event listeners (are they also producers?) confuses me; it seems that there's more to the game engine. Even some general ideas would help. TIA.

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• MVP on Asp.Net WebForms

  - by Nicolas Irisarri

  I'm not clear about this.... When having a gridview on the View, is the controller who has to set up the Data source, columns, etc? or I just have to expose the DataBinding stuff, fire it from the controller and let the html/codebehind on the view handle all the rendering and wiring up? To be more precise: on the view should I have private GridView _gv public _IList<Poco> Source { get {_gv.DataSource;} set {_gv.DataSource = value; _gv.DataBind();} } Or should it be (from http://stackoverflow.com/questions/153222/mvp-pattern-passive-view-and-exposing-complex-types-through-iview-asp-net-web) private GridView _datasource; public DataSource { get { return _datasource; } set { _datasource = value; _datasource.DataBind(); } } Maybe I'm having it all wrong .... Where can I find an example that is not a "Hello world" example on MVP for ASP.Net???

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• Dictionary returning a default value if the key does not exist

  - by wasatz

  I find myself using the current pattern quite often in my code nowadays var dictionary = new Dictionary<type, IList<othertype>>(); // Add stuff to dictionary var somethingElse = dictionary.ContainsKey(key) ? dictionary[key] : new List<othertype>(); // Do work with the somethingelse variable Or sometimes var dictionary = new Dictionary<type, IList<othertype>>(); // Add stuff to dictionary IList<othertype> somethingElse; if(!dictionary.TryGetValue(key, out somethingElse) { somethingElse = new List<othertype>(); } Both of these ways feel quite roundabout. What I really would like is something like dictionary.GetValueOrDefault(key) Now, I could write an extension method for the dictionary class that does this for me, but I figured that I might be missing something that already exists. SO, is there a way to do this in a way that is more "easy on the eyes" without writing an extension method to dictionary?

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• Python dictionary: add or increment entry

  - by cursa

  Hi everyone, I'm currently re-engaging with Python after a long absence and loving it. However, I find myself coming across a pattern over and over. I keep thinking that there must be a better way to express what I want and that I'm probably doing it the wrong way. The code that I'm writing is in the following form: # foo is a dictionary if foo.has_key(bar): foo[bar] += 1 else: foo[bar] = 1 I'm writing this a lot in my programs. My first reaction is to push it out to a helper function, but so often the python libraries supply things like this already. Is there some simple little syntax trick that I'm missing? Or is this the way that it should be done?

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• Silverlight Navigation using Mvvm-light(oobe)+MEF?

  - by deliberative assembly

  What is the best approach for navigating between UserControls/Pages(out of browser experience)? I'm fairly new to Silverlight and even newer to the mvvm pattern. How well does the Navigation Framework Integrate with the MVVM Light Toolkit? A snippet for general application flow control with the two would be great. The plan was to use the Navigation Framework for general flow or using Jeremy Likeness's approach to region management(http://csharperimage.jeremylikness.com/search/label/regions) and swapping out regions as needed. I've seen a few places mention replacing the Visual Root, but that sounded like a hack to me. Any advice, snippets, or a nudge in the general direction would be greatly appreciated. Thank you.

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• What is JDBC's Connection.isClosed() good for, and why is Snaq DBPool misbehaving on close?

  - by Uri

  I have the following code in Java: if(!conn.isClosed()) { conn.close(); } Instead of working, I am awarded with: java.sql.SQLException: Connection already closed My connection object is a Snaq.db.CacheConnection I checked the JavaDocs for isClosed, and they state that: This method generally cannot be called to determine whether a connection to a database is valid or invalid. A typical client can determine that a connection is invalid by catching any exceptions that might be thrown when an operation is attempted. So my questions are: 1) What good is JDBC's isClosed() anyway? Since when do we use Exceptions in Java to check for validity? 2) What is the correct pattern to close a database? Should I just close and swallow exceptions? 3) Any idea why would SnaqDB be closing the connection? (My backend is a Postgres 8.3)

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