What is the best way to implement Singleton Design Pattern in C# with performance constraint?
- by markattwood
Hi,
Please let me know what the best way to implement Singleton Design Pattern in C# with performance constraint?
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Search found 8692 results on 348 pages for 'patterns practices'.
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why copy and paste codes is dangerous
- by Yigang Wu
sometimes, my boss will complain us why we need so long time to implement a feature, actually, the feature has been implemented in other AP before, you just need to copy and paste codes from there. The cost should be low. It's really a hard question, because copy and paste codes is not a easy thing from my point. Do you have any good reason to explain your boss who doesn't know technology?Read the article
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Best way to force Spring shutdown from a bean?
- by xcut
My application uses a Spring DefaultMessageListenerContainer to process incoming messages. The main method of the app already registers a shutdown hook. Question is this: what is the best way to force the application context to shut down? If I throw a RuntimeException in the message listener, it is handled by the container, and not passed on. Is calling System.exit acceptable? Do I pass along the ApplicationContext to every class that needs to shut down, so I can call close() on it?Read the article
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What is the reason not to use select * ?
- by Chris Lively
I've seen a number of people claim that you should specifically name each column you want in your select query. Assuming I'm going to use all of the columns anyway, why would I not use SELECT *? Even considering the question from 9/24, I don't think this is an exact duplicate as I'm approaching the issue from a slightly different perspective. One of our principles is to not optimize before it's time. With that in mind, it seems like using SELECT * should be the preferred method until it is proven to be a resource issue or the schema is pretty much set in stone. Which, as we know, won't occur until development is completely done. That said, is there an overriding issue to not use SELECT *?Read the article
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Is this multi line if statement too complex?
- by AndHeCodedIt
I am validating input on a form and attempting to prompt the user of improper input(s) based on the combination of controls used. For example, I have 2 combo boxes and 3 text boxes. The 2 combo boxes must always have a value other than the first (default) value, but one of three, or two of three, or all text boxes can be filled to make the form valid. In one such scenario I have a 6 line if statement to try to make the test easily readable: if ((!String.Equals(ComboBoxA.SelectedValue.ToString(), DEFAULT_COMBO_A_CHOICE.ToString()) && !String.IsNullOrEmpty(TextBoxA.Text) && !String.Equals(ComboBoxB.SelectedValue.ToString(), DEFAULT_COMBO_B_CHOICE.ToString())) || (!String.IsNullOrEmpty(TextBoxB.Text) || !String.IsNullOrEmpty(TextBoxC.Text))) { //Do Some Validation } I have 2 questions: Should this type of if statement be avoided at all cost? Would it be better to enclose this test in another method? (This would be a good choice as this validation will happen in more than one scenario) Thanks for your input(s)!Read the article
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Why is Visual Basic used?
- by Arrieta
I don't mean to start a holy war here, but I cannot fathom why would anybody use Visual Basic for a new project. Can you explain me why is it used? What new applications (which a lay person may be familiar with) have been developed in it? Why is it chosen over other languages? Thanks.Read the article
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Alternative to jQuery .data()?
- by thebossman
I'm a big fan of jQuery's .data() method, but I can't always use it. Often times I am rendering html templates that I pass via AJAX and I need to attach metadata to each of the elements in the template. For example: <ul> {% for item in itemlist %} <li metadata="{{ item.metadata }}">{{ item.name }}</li> {% endfor %} </ul> I know attaching attributes to store data is bad practice (and it might not even work in older versions of IE). What is the best practice? Is there a good alternative to this method?Read the article
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Best practice: How to persist simple data without a database in django?
- by Infinity
I'm building a website that doesn't require a database because a REST API "is the database". (Except you don't want to be putting site-specific things in there, since the API is used by mostly mobile clients) However there's a few things that normally would be put in a database, for example the "jobs" page. You have master list view, and the detail views for each job, and it should be easy to add new job entries. (not necessarily via a CMS, but that would be awesome) e.g. example.com/careers/ and example.com/careers/77/ I could just hardcode this stuff in templates, but that's no DRY- you have to update the master template and the detail template every time. What do you guys think? Maybe a YAML file? Or any better ideas? ThxRead the article
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Why is 'virtual' optional for overridden methods in derived classes?
- by squelart
When a method is declared as virtual in a class, its overrides in derived classes are automatically considered virtual as well, and the C++ language makes this keyword virtual optional in this case: class Base { virtual void f(); }; class Derived : public Base { void f(); // 'virtual' is optional but implied. }; My question is: What is the rationale for making virtual optional? I know that it is not absolutely necessary for the compiler to be told that, but I would think that developers would benefit if such a constraint was enforced by the compiler. E.g., sometimes when I read others' code I wonder if a method is virtual and I have to track down its superclasses to determine that. And some coding standards (Google) make it a 'must' to put the virtual keyword in all subclasses.Read the article
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Finding databases for use in applications
- by JonF
Does anyone have some recommendations on how I can find databases for random things that I might want to use in my application. For example, a database of zip code locations, area code cities, car engines, IP address locations, or whatever. I'm just asking generally when you decide you need a bunch of data where are some good places to start looking other than google?Read the article
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Is it a good practice to perform direct database access in the code-behind of an ASP.NET page?
- by patricks418
Hi, I am an experienced developer but I am new to web application development. Now I am in charge of developing a new web application and I could really use some input from experienced web developers out there. I'd like to understand exactly what experienced web developers do in the code-behind pages. At first I thought it was best to have a rule that all the database access and business logic should be performed in classes external to the code-behind pages. My thought was that only logic necessary for the web form would be performed in the code-behind. I still think that all the business logic should be performed in other classes but I'm beginning to think it would be alright if the code-behind had access to the database to query it directly rather than having to call other classes to receive a dataset or collection back. Any input would be appreciated.Read the article
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Does database affect classes?
- by satyanarayana
I had created one class User and UserDAOImpl class for querying DB using class User. As there is one table to be queried, these two classes are sufficient for me. What if there is a case where new fields are to be added to that one table is to be divided into 3 tables( user_info, user_profile and user_address) to store user? As new fields are added, I need to change classes User and UserDAOImpl, it seems these two are not sufficient. It seems database changes affect my classes. In this case, do I need to divide class User into 3 classes as tables are changes? Can any one suggest me how can I solve this without making too many changes?Read the article
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Building a life-critical System using Agile
- by Ben Breen
Looking at the general trend of comments in my question about Building an Aircraft using Agile, the biggest problem other than cost appears to be safety. Do people feel that it is not possible to build a safe system (or prove it is safe) using agile? Doesn’t all the iterative testing mitigate this? Is it likely that a piece of software developed using agile will never be as reliable as counterparts such as waterfall?Read the article
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Am I using too much jQuery? When am I crossing the line?
- by Andrea
Lately I found myself using jQuery and JavaScript a lot, often to do the same things that I did before using CSS. For example, I alternate table rows color or create buttons and links hover effects using JavaScript/jQuery. Is this acceptable? Or should I keep using CSS for these kinds of things? So the real question is: When I'm using too much jQuery? How can I understand when I'm crossing the line?Read the article
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Accessing the "super of this" in Java
- by gerdemb
This is what I'm doing now. Is there a better way to access the super class? public class SearchWidget { private void addWishlistButton() { final SearchWidget thisWidget = this; button.addClickHandler(new ClickHandler() { public void onClick(ClickEvent event) { // A better way to access the super class? // something like "this.super" ...? workWithWidget(thisWidget); } } } } I'm programming with Google Web Toolkit, but I think this is really a generic Java question.Read the article
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MapReduce programming system in java-actionscript
- by eco_bach
Just finished reading ch23 in the excellent 'Beautiful Code' http://oreilly.com/catalog/9780596510046 on Distributed Programming with MapReduce. I understand that MapReduce is a programming system designed for large-scale data processing problems, but I have a hard time getting my head around the basic examples given and how I might apply them in real world situations. Can someone give a simple example of MapReduce implemented using either java, javascript or actionscript?Read the article
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Is there a design pattern that expresses objects (an their operations) in various states?
- by darren
Hi I have a design question about the evolution of an object (and its state) after some sequence of methods complete. I'm having trouble articulating what I mean so I may need to clean up the question based on feedback. Consider an object called Classifier. It has the following methods: void initialise() void populateTrainingSet(TrainingSet t) void pupulateTestingSet(TestingSet t) void train() void test() Result predict(Instance i) My problem is that these methods need to be called in a certain order. Futher, some methods are invalid until a previous method is called, and some methods are invalid after a method has been called. For example, it would be invalid to call predict() before test() was called, and it would be invalid to call train() after test() was called. My approach so far has been to maintain a private enum that represents the current stateof the object: private static enum STATE{ NEW, TRAINED, TESTED, READY}; But this seems a bit cloogy. Is there a design pattern for such a problem type? Maybe something related to the template method.Read the article
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Bad Design? Constructor of composition uses `this`
- by tanascius
Example: class MyClass { Composition m_Composition; void MyClass() { m_Composition = new Composition( this ); } } I am interested in using depenency-injection here. So I will have to refactor the constructor to something like: void MyClass( Composition composition ) { m_Composition = composition; } However I get a problem now, since the Composition-object relies on the object of type MyClass which is just created. Can a dependency container resolve this? Is it supposed to do so? Or is it just bad design from the beginning on?Read the article
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Returning back to the results after editing
- by Parhs
Hello, I am developing an application which has several CRUD actions... I am using Java and i am forced to use Struts framework. My problem is: I have a search page which returns some results.The user can click at a result and then he goes to another edit-page... He may apply changes or not...What i need is a way to return at the result page again and at the same scroll position.Javascript must be enabled for this project however.. I am wondering which is the best practice to achieve this effect... A solution would be to save the last search URL but i know that this wouldnt work if the user has multiple results. I know how to do it but i am lloking for a good practice!Read the article
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Performing centralized authorization for multiple applications
- by Vaibhav
Here's a question that I have been wrestling with for a while. We have a situation wherein we have a number of applications that we have created. These have grown organically over a period of time. All of these applications have permissions code built into them that controls access to various parts of the application depending on whether the currently logged in user has the necessary permissions or not. Alongside these applications is a utility application which allows an administrator to map users to permissions for all applications - the way it works is that every application has code which reads this external database of the said utility application to check if the currently logged in user has the necessary permission or not. Now, the question is this. Should the user-permissions mapping information reside in and be owned by the applications themselves, or is it okay to have this information reside within an external entity/DB (as in this case the utility application's database). Part of me thinks that application permissions are very specific to the application context itself, so shouldn't be separated from the application itself. But I am not sure. Any comments?Read the article
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C# Design Reduce a Long List of Methods
- by guazz
I have a simple application that loads data from an XML file to a database. public class EmployeeLoader() { public void LoadEmpoyees() {...} public void LoadSalaries() {...} public void LoadRegistrationData() {...} public void LoadTaxData() {...} } Is it a good idea to have multiple "Load" methods as this looks like a code smell as I have about tweney Load methods? If so, how do I make my code more readable? Each Load method loads data to the corresponding table in the database via a repository?Read the article
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Should I *always* import my file references into the database in drupal?
- by sprugman
I have a cck type with an image field, and a unique_id text field. The file name of the image is based on the unique_id. All of the content, including the image itself is being generated automatically via another process, and I'm parsing what that generates into nodes. Rather than creating separate fields for the id and the image, and doing an official import of the image into the files table, I'm tempted to only create the id field and create the file reference in the theme layer. I can think of pros and cons: 1) Theme Layer Approach Pros: makes the import process much less complex don't have to worry about syncing the db with the file system as things change more flexible -- I can move my images around more easily if I want Cons: maybe not as much The Drupal Way™ not as pure -- I'll wind up with more logic on the theme side. 2) Import Approach Pros: import method is required if we ever wanted to make the files private (we won't.) safer? Maybe I'll know if there's a problem with the image at import time, rather than view time. Since I'll be bulk importing, that might make a difference. if I delete a node through the admin interface, drupal might be able to delete the file for me, as well. Con: more complex import and maintenance All else being equal, simpler is always better, so I'm leaning toward #1. Are there any other issues I'm missing? (Since this is an open ended question, I guess I'll make it a community wiki, whatever that means.)Read the article
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Tool that auto-generate a code for accesing a xml-file
- by alex
My application have a configuration xml-file. That file contains more than 50 program settings. At the present time I read and save each program setting separately. I guess It is not effi?iently for such tasks. I need something that can auto-generate a code for load and save my program settings using predefined xml-schema. I found a dataset in Add New Item dialog. Unfortunately, i cannot add new code to dataset1 such as events in set-accessors of properties because of this // Changes to this file may cause incorrect behavior and will be lost if // the code is regenerated. Maybe, there is a tool that allows a user to generate a wrapper for accesing a xml-file ? Such as DataSet1, but with availability to add events.Read the article
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Comparing objects and inheritance
- by ereOn
Hi, In my program I have the following class hierarchy: class Base // Base is an abstract class { }; class A : public Base { }; class B : public Base { }; I would like to do the following: foo(const Base& one, const Base& two) { if (one == two) { // Do something } else { // Do something else } } I have issues regarding the operator==() here. Of course comparing an instance A and an instance of B makes no sense but comparing two instances of Base should be possible. (You can't compare a Dog and a Cat however you can compare two Animals) I would like the following results: A == B = false A == A = true or false, depending on the effective value of the two instances B == B = true or false, depending on the effective value of the two instances My question is: is this a good design/idea ? Is this even possible ? What functions should I write/overload ? My apologies if the question is obviously stupid or easy, I have some serious fever right now and my thinking abilities are somewhat limited :/ Thank you.Read the article
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using ref to view error
- by Avram
Hello. I working now on firm that using ref in every function. The reason, is to catch errors. There example : //return true if the read is success //otherwise writing to the error ,the problem bool ReadFile(ref string error) Question: How do you catching errors? Using ref,exceptions or other way?Read the article
