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• 'e-Commerce' scalable database model

  - by Ruben Trancoso

  I would like to understand database scalability so I've just heard a talk about Habits of Highly Scalable Web Applications http://techportal.ibuildings.com/2010/03/02/habits-of-highly-scalable-web-applications/ On it, the presenter mainly talk about relational database scalability. I also have read something about MapReduce and Column oriented tables, big tables, hypertable etc... trying to understand which are the most up to date methods to scale web application data. But the second group, to me, is being hard to understand where it fits. It serves as transactional, reliable data store? or not, its just for large access and processing and to handle fine graned operations we will ever need to rely on RDBMSs? Could someone give a comprehensive landscape for those new technologies and how to use it?

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• VS2010's "Public Property <PropertyName> As <DataType> vs. Public var

  - by Velika2

  In VS2008, I used to type Public Property <PropName> As <dataType> and hit the Enter key and the IDE editor would automatically expand it out to a full blown property block. Now, from what I understand, a new feature of 2010 is that the compiler automatically "expands" the short syntax above into the same IL code that you would get with the full property GET AND SET sub methods that were are accustomed to seeing before in the editor. But functionality, how the heck is this any different than just having a Public class level variable? If the only diff is what it compiles to and if otehrwise there is no functional difference, isn't the new way less efficient than the old since it involves more code than just having a class level memory variable? Public as I thought that if you weren't going to have code behind your properties that they were essentially the same. I guess the diffrenece is that they just added the keyword "Property" but functionality, their is no diff, eh?

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• Iterative / Additive MD5

  - by Andrew Robinson

  I need to generate a checksum over a dictionary. Keys and Values. Is there any simple way to accomplish this in an iterative way. foreach(var item in dic.Keys) checksum += checksum(dic[item]) + checksum(item); In this case, keys and values could be converted to strings, concatinated and then a single checksum applied over these but is there a better way? Ideally MD5 but other options could work. Using this to validate data that is passed over a couple of storage methods. The checksum is then encrypted along with some other information (using AES) so I am not horribly worried about an ideal, unbreakable checksum.

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• Is it possible to create thread-safe collections without locks?

  - by Andrey

  This is pure just for interest question, any sort of questions are welcome. So is it possible to create thread-safe collections without any locks? By locks I mean any thread synchronization mechanisms, including Mutex, Semaphore, and even Interlocked, all of them. Is it possible at user level, without calling system functions? Ok, may be implementation is not effective, i am interested in theoretical possibility. If not what is the minimum means to do it? EDIT: Why immutable collections don't work. This of class Stack with methods Add that returns another Stack. Now here is program: Stack stack = new ...; ThreadedMethod() { loop { //Do the loop stack = stack.Add(element); } } this expression stack = stack.Add(element) is not atomic, and you can overwrite new stack from other thread. Thanks, Andrey

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• show definition (browse) in *.pdb of *.dll file

  - by ala

  I have built a Library project (DLL) in .NET. And sometimes I use the DLL along with its PDB file as a reference in some other projects. Now in the new project, I cant browse through the code of the DLL to debug. I can only see the definitions of class/methods/variables. That's by using "show definition" by browsing through the "class view" However, only in case of an exception I the contents of the DLL opens and I could see the entire code of the DLL from the new project. How could I see the contents (code) of the DLL before an exception occur?

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• What is the difference between File and FileInfo in C# ?

  - by Lilitu88

  I've been reading that the static methods of the File Class are better used to perform small and few tasks on a file like checking to see if it exists and that we should use an instance of the FileInfo Class if we are going to perform many operations on a specific file. I understand this and can simply use it that way blindly but I would like to know why is there a difference ? What is it about the way they work that make them suitable for different situations ? What is the point of having this 2 different classes that seem do the same in different ways ? It would be helpful if someone could answer at least one of this questions.

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• Problem with lazy loading implementation

  - by Mehran

  Hi, I have implemented lazy loading in my program. it's done through a proxy class like: class Order { public virtual IList<Item> Items {get; set;} } class OrderProxy { public override IList<Item> Items { get { if (base.Items == null) Items = GetItems(base.OrderID); return base.Items; } set { base.Items = value; } } } the problem is that whenever i instantiate proxy class,without even touching the Items property, it tries to load Items! as you may know,i want to instantiate proxy class and return the instance to BLL instead of domain object itself. what's the problem? Does .NET CLR access(read) properties in a class, when it's instatiating the class? any other methods? Thanks

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• how to compare between Doctrine & Propel in symfony

  - by Patrick

  I am in the early stages of rearchitecting my company's application. The app is currently running on symfony 1.2, and I used the default ORM at the time, Propel. Symfony has since updated to 1.4 and switched default ORM to Doctrine. From my understanding, each ORM excels at particular types of database structures. Is this true or is one far and away better than the other? Are there any good methods to test which ORM would be best in my situation in a test environment using my schema (i.e.- set up dual, identical sites and run tests)?

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• How is method group overload resolution different to method call overload resolution?

  - by thecoop

  The following code doesn't compile (error CS0123: No overload for 'System.Convert.ToString(object)' matches delegate 'System.Converter<T,string>'): class A<T> { void Method(T obj) { Converter<T, string> toString = Convert.ToString; } } however, this does: class A<T> { void Method(T obj) { Converter<T, string> toString = o => Convert.ToString(o); } } intellisense gives o as a T, and the Convert.ToString call as using Convert.ToString(object). In c# 3.5, delegates can be created from co/contra-variant methods, so the ToString(object) method can be used as a Converter<T, string>, as T is always guarenteed to be an object. So, the first example (method group overload resolution) should be finding the only applicable method string Convert.ToString(object o), the same as the method call overload resolution. Why is the method group & method call overload resolution producing different results?

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• Update User Info with restful_authentication plugin in Rails?

  - by benoror

  Hi people, I want to give the users the ability to change their account info with restful_authentication plugin in rails. I added this two methods to my users controller: def edit @user = User.find(params[:id]) end def update @user = User.find(params[:id]) # Only update password when necessary params[:user].delete(:password) if pàrams[:user][:password].blank? respond_to do |format| if @user.update_attributes(params[:user]) flash[:notice] = 'User was successfully updated.' format.html { redirect_to(@user) } format.xml { head :ok } else format.html { render :action => "edit" } format.xml { render :xml => @user.errors, :status => :unprocessable_entity } end end end Also, I copied new.html.erb to edit.html.erb. Considering that resources are already defined in routes.rb I was expecting it to work easily, bute somehow when I click the save button it calls the create method, instead of update, using a POST http request. Inmediatly after that it autocatically log out form the session. Any ideas?

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• Document ranking strategy for P2P file sharing system.

  - by ablmf

  Recently, I got a task of building a P2P file sharing system. There is one requirement : the system should have a document ranking algorithm so that it could be used help users find more valuable files. Several strategy might be useful : force user to give a score to a file before it was downloaded The documents containing certain key words would get higher rank Manager could modify file ranking manually the more a file was downloaded, it would get a higher rank. Do you know any other strategy or methods that also appropriate? Or is there any real world example?

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• Watin File Download Problem

  - by EmrahIlker

  When I clicked button with mouse, File Download Dialog opens directly. But when Watin Button Click methods click the vert same button on same ie window this message appears and wait my confirm To help protect your security, Internet Explorer blocked this site from downloading files to your computer. Click here for options. I turned off the Information bar for file downloads,(Internet Options-Security-Custom Level-Downloads-Automatic prompting for file downloads--Enable),allow active x content, lower security level for internet etc.. but didn't work. I'm using Win 7, IE8.

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• Subsonic 3.0 - .Net - Error : Can not ceate an instance of an interface

  - by George

  Hi, I am new to Subsonic, I have configured Subsonic3.0 T4 Template and created classes for my project. I have taken GridView and Object Datasource. Object datasource will connect to the one of the classes which is created from subsonic. I have set object datasource for g\fetch, Insert, Update and delete methods. Then i set the datasource of grid witht he object datasource. Grid view successfully showing me all the records. But at the time of Update, Insert or delete it throws an exception that "Can not ceate an instance of an interface". And also i am not able to dwbug in the code of the subsonic. May be because of partial classes. Can anyone please let me know what is happening at the backgrund? Or may be one can give me sample example which contains subsonic 3.0 and grid add, edit and delete so it will be really helpful for me.... Please... :) Thanks, George

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• Why .NET Boolean has TrueLiteral and TrueString?

  - by user309937

  Why in Boolean type there are two fields with the same value? internal const int True = 1; internal const int False = 0; internal const string TrueLiteral = "True"; internal const string FalseLiteral = "False"; and public static readonly string TrueString; public static readonly string FalseString; static Boolean() { TrueString = "True"; FalseString = "False"; } in reflector generated code, methods don't use those strings but: public string ToString(IFormatProvider provider) { if (!this) { return "False"; } return "True"; } would't it be better to use those const values?

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• Objects in interface

  - by Peter Kowalchuk

  I created my own object, PKSurvey. In the interface of the View Controller I can define a pointer to it, then in a method I can alloc it and have an instance. How do I keep the instance beyond the method where it was allocated? I assign values in one method and want to be able to use those values in other methods. Should I allocate it in the viewDidLoad method or should I do it somewhere else? @interface DIrectionalDrillerViewController : UIViewController { PKSurvey *Survey=[PKSurvey new]; ---------------- - (void)viewDidLoad { [Survey new];

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• Rails - building an absolute url in a model's virtual attribute without url helper

  - by Nick

  I have a model that has paperclip attachments. The model might be used in multiple rails apps I need to return a full (non-relative) url to the attachment as part of a JSON API being consumed elsewhere. I'd like to abstract the paperclip aspect and have a simple virtual attribute like this: def thumbnail_url self.photo.url(:thumb) end This however only gives me the relative path. Since it's in the model I can't use the URL helper methods, right? What would be a good approach to prepending the application root url since I don't have helper support? I would like to avoid hardcoding something or adding code to the controller method that assembles my JSON. Thank you

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• VB.net: Is my Thread Safe List Solution actually safe?

  - by Shiftbit

  I've added teh following Extensions to my Project in order to create a thread safe list: Extensions If I want to conduct a simple operation on my list <Extension()> _ Public Sub Action(Of T)(ByVal list As List(Of T), ByVal action As Action(Of List(Of T))) SyncLock (list) action(list) End SyncLock End Sub If I want to pass it more than one parameter I could simply extend it with more items... <Extension()> _ Public Sub Action(Of T)(ByVal list As List(Of T), ByVal action As Action(Of List(Of T), T), ByVal item As T) SyncLock (list) Action(list, item) End SyncLock End Sub Actions I have created the following Action Examples: Private Sub Read(Of T)(ByVal list As List(Of T)) Console.WriteLine("Read") For Each item As T In list Console.WriteLine(item.ToString) Thread.Sleep(10) Next End Sub and also one that takes a parameter: Private Sub Write(Of T)(ByVal list As List(Of T), ByVal item As T) Thread.Sleep(100) list.Add(item) Console.WriteLine("Write") End Sub Initiating Then in my various threads I will call my Actions with: list.Action(AddressOf Read) or list.Action(AddressOf Write2, 10) Are these Extenxion methods thread safe or do you have other recommendations?

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• Testing file existence using NSURL

  - by Peter Hosey

  Snow Leopard introduced many new methods to use NSURL objects to refer to files, not pathnames or Core Services' FSRefs. However, there's one task I can't find a URL-based method for: Testing whether a file exists. I'm looking for a URL-based version of -[NSFileManager fileExistsAtPath:]. Like that method, it should return YES if the URL describes anything, whether it's a regular file, a directory, or anything else. I could attempt to look up various resource values, but none of them are explicitly guaranteed to not exist if the file doesn't, and some of them (e.g., NSURLEffectiveIconKey) could be costly if it does. I could just use NSFileManager's fileExistsAtPath:, but if there's a more modern method, I'd prefer to use that. Is there a simple method or function in Cocoa, CF, or Core Services that's guaranteed/documented to tell me whether a given file (or file-reference) URL refers to a file-system object that exists?

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• Can Fluent nhibernate's automapper be configured to handle private readonly backing fields?

  - by Mark Rogers

  I like private readonly backing fields because some objects are mostly read-only after creation, and for collections, which rarely need to be set wholesale (instead using collection methods to modify the collection). For example: public class BuildingType : DomainEntity { /* rest of class */ public IEnumerable<ActionType> ActionsGranted { get { return _actionsGranted; } } private readonly IList<ActionType> _actionsGranted = new List<ActionType>(); private readonly Image _buildingTile; public virtual Image BuildingTile { get { return _buildingTile; } } } But as far as I remember fluent-nhibernate's automapper never had a solution for private readonly backing fields, I'm wondering if that's changed in the last few months. So here's my question: How do I configure automapper or create an automapping convention to map private readonly backing fields?

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• Drupal 7: cancel user registration if a wrong field value has been submitted.

  - by Alexander Farber

  Hello, I have a Drupal 7 with 1 field added to registration form - a List with possible values Robot / Male / Female: # select * from field_data_field_gender; entity_type | bundle | deleted | entity_id | revision_id | language | delta | field_gender_value -------------+--------+---------+-----------+-------------+----------+-------+-------------------- user | user | 0 | 6 | 6 | und | 0 | Male user | user | 0 | 5 | 5 | und | 0 | Male user | user | 0 | 7 | 7 | und | 0 | Female user | user | 0 | 1 | 1 | und | 0 | Male The first value Robot is a default value - to prevent SPAM robots from registering at my site. Is there a way to cancel user registration, when a new user submits the registration web form with the default Robot value? (i.e. only Male and Female values are allowed). I've looked at the core Trigger module, but don't see anything suitable there. I've looked at the hook_user_presave and hook_user_insert API docs, but don't see a way there to cancel an ongoing user registration. (I was expecting to do that by returning a special value from those methods...) Thank you! Alex

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• can't see the result after i update a row in a table in a gridview

  - by aleo

  Peace! i created a gridview and ive bended the data using a ObjectDataSource, for some reasons i created the CRUD methods to do the work instead of using the CRUD method generated by the LINQDataSource; everything is just working fine but the update method, when i update a row in my gridview everything become as if there isnt any update! but when i check the database i can see that the rows is been updated! i can't find a solution (yet) to this issue. i'am using the updatepanel to have the autopostback without refreshing the page. thank you

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• Weird use of generics

  - by Karl Trumstedt

  After a bit of programming one of my classes used generics in a way I never seen before. I would like some opinions of this, if it's bad coding or not. abstract class Base<T> : where T : Base<T> { // omitted methods and properties. virtual void CopyTo(T instance) { /*code*/ } } class Derived : Base<Derived> { override void CopyTo(Derived instance) { base.CopyTo(instance); // copy remaining stuff here } } is this an OK use of generics or not? I'm mostly thinking about the constraint to "itself". I sometimes feel like generics can "explode" to other classes where I use the Base class.

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• Difference between two commands of fetching Shopping Cart Items in Magento

  - by Knowledge Craving

  In Magento, if you need to get / fetch the Shopping Cart's Item details, you can do it in any of the two possible ways, which will provide you with all the shopped Items in an array:- $cartItems1 = $cart->getQuote()->getAllItems(); $cartItems2 = $cart->getItems()->getData(); But before using any one of the above two methods, you need to initialize the shopping cart object as:- $cart = new Mage_Checkout_Model_Cart(); $cart->init(); Can anyone please describe in details as to what the two options provide & their differences between each other, along with their possible usage. In any more such option is available in Magento, can anyone please highlight it?

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• C++ and Scripting.Dictionary from scrrun.dll

  - by MaxFX

  Hello. I have some trouble with Scripting.Dictionary in C++. I'm trying to use interface IDictionary via smart pointer but methods of creating object don't work and I can't understand why. CoInitialize(NULL); IDictionaryPtr dict; dict.CreateInstance(__uuidof(Dictionary)); _variant_t num1 = 1; _variant_t num2 = 2; dict->Add(&num1, &num2); long i; dict->get_Count(&i); cout << i << "\n"; But method Add does not work and cout of elements in dictionary is always 0. How correct to use Scripting.Dictionary in that case. PS.: I'm getting Scripting interfaces by #import "scrrun.dll"

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• How does the method overload resolution system decide which method to call when a null value is passed?

  - by Joan Venge

  So for instance you have a type like: public class EffectOptions { public EffectOptions ( params object [ ] options ) {} public EffectOptions ( IEnumerable<object> options ) {} public EffectOptions ( string name ) {} public EffectOptions ( object owner ) {} public EffectOptions ( int count ) {} public EffectOptions ( Point point ) {} } Here I just give the example using constructors but the result will be the same if they were non-constructor methods on the type itself, right? So when you do: EffectOptions options = new EffectOptions (null); which constructor would be called, and why? I could test this myself but I want to understand how the overload resolution system works (not sure if that's what it's called).

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