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• What happens when you create an instance of an object containing no state in C#?

  - by liquorice

  I am I think ok at algorithmic programming, if that is the right term? I used to play with turbo pascal and 8086 assembly language back in the 1980s as a hobby. But only very small projects and I haven't really done any programming in the 20ish years since then. So I am struggling for understanding like a drowning swimmer. So maybe this is a very niave question or I'm just making no sense at all, but say I have an object kind of like this: class Something : IDoer { void Do(ISomethingElse x) { x.DoWhatEverYouWant(42); } } And then I do var Thing1 = new Something(); var Thing2 = new Something(); Thing1.Do(blah); Thing2.Do(blah); does Thing1 = Thing2? does "new Something()" create anything? Or is it not much different different from having a static class, except I can pass it around and swap it out etc. Is the "Do" procedure in the same location in memory for both the Thing1(blah) and Thing2(blah) objects? I mean when executing it, does it mean there are two Something.Do procedures or just one?

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• How do I obtain an HtmlHelper<TModel> instance for a model in ASP.NET MVC?

  - by DanM

  Let's say I have an Index view. The model I pass in is actually a collection of models, so the Html property is of type HtmlHelper<List<MyModel>>. If I want to call extension methods (e.g., Display() or DisplayFor() on the individual items in the list, however, I think I need to obtain an HtmlHelper<MyModel>. But how? I tried using the HtmlHelper<TModel> constructor, which looks like this: HtmlHelper<TModel>(ViewContext, IViewDataContainer) But I'm not having any luck with that. I don't know how to obtain the IViewDataContainer for the item, and the documentation on these things is very sparse. A lot of magic apparently happens when I do... return View(List<MyModel>); ...in my controller. How do I recreate that magic on individual items in a list/collection?

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• mysql and php: setting config variables on start - impact on server?

  - by andufo

  date_default_timezone_set('America/Guayaquil'); $cnn->execute('SET NAMES utf8'); $cnn->execute('SET GLOBAL time_zone = "-5:00"'); Hi, the code above is run everytime someone enters the website im developing. Does someone know what the impact (in performance) of those commands is?

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• What is the best way to pass server side variables to JavaScript on the client side?

  - by steve_c

  Our application uses a lot of configuration options. Those options need to be reflected on the client side in the form of User preferences, site wide preferences, etc. Currently, we pass server side settings down to the client side in the form of JSON that is stored in custom attributes in the markup for a specific element (and no, our application currently doesn't worry about W3C validation). We then retrieve the data from the custom attribute, and parse it into a JSON object for use in script using jQuery. One drawback to this is referencing attributes on elements from within event handlers. I know this is frowned upon, as it can create circular references, and subsequently memory leaks. I would much prefer to use jQuery's data function, but you can't invoke this from the server side at page render time. What does everyone else do in this type of scenario?

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• How to use a C array as instance variable?

  - by mystify

  For example I want to store this in an ivar: CGFloat color[4] = {red, green, blue, 1.0f}; so would I put this in my header? CGFloat color[]; How would I assign values to that guy later? I mean I can't change it, right?

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• How to use php variables (arrays) in mysql select statements?

  - by davidconn

  Hi everybody, How do you use a php variable (array) inside a mysql select statement? I am designing an auction site and currently working on a page that lets people view a list of all the current bids for an item. I want to display 3 columns: amountbid - the amount each bidder has bid for the item (held in tblbid) bidderid - the id of each bidder who has bid (found in tbluser) total_positivity_feedback - how many users have left positive feedback for the bidder (calculated from tblfeedback) To find the 'amount' and the 'bidderid' columns i pass the essayid URL parameter from the previous page. This works fine. Despite this, i can't display the total_positivity_feedback column for the various users who have made each bid. My mysql query looks like this: select tblbid.bidderid, tblbid.amount, (select count(tblfeedback.feedbackid) from tblfeedback WHERE tblfeedback.writerid = "ARRAY VARIABLE GOES HERE") AS total_positivity_feedback FROM tblbid WHERE tblbid.essayid = $essayid_bids I assume that the only way to accomplish this is to make the variable contain the bidderid's of those people who bid for that particular essay? I can't seem to work out how to do this tho?!? Many thanks for your help

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• Should we have separate database instance for each developer?

  - by Amitabh

  What is the best way for developing a database based application? We can have two approaches. One common database for all the developers. List item Separate database for all the developers. What are the pros and cons of each? And which one is better way?

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• Can I Use EF Across Multiple DBs in One SQLServer Instance?

  - by thomashubschman

  Hello, I have been searching the blogs and articles but I have not found much support for this scenario. I have been poking around EF and realized that I could create views that contained data from multiple databases and then build the EF object model off of those views. Although it works I am not sure about the usual issues of performance, scalability, maintainability. The way I am achieving the connection between databases is by creating associations in the EF model. Does anyone have any information about this type of implementation? Either another solution or commentary on this proposed solution? Thanks, Tom

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• Staticly linked libraries not running code inside to setup static variables.

  - by MJD

  In a c++ project I am working on, I have a simple c++ file that needs to run some code at the beginning of the progam execution. This file is linked into a static library, which is then linked into the main program. I have similar code in other files running fine, that looks something like: bool ____nonexistant_value = executeAction(); However, it does not work inside this file unless I make use of a function implemented in this file. It does work if the library is compilied as a shared library. I'd prefer to link this statically as the library is only a convience as the file is in a different directory.

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• Call a non member funcion on an instance before is constructed.

  - by Tom

  Hi everyone. I'm writing a class, and this doubt came up. Is this undef. behaviour? On the other hand, I'm not sure its recommended, or if its a good practice. Is it one if I ensure no exceptions to be thrown in the init function? //c.h class C{ float vx,vy; friend void init(C& c); public: C(); ~C(); }; //c.cpp C::C() { init(*this); } void init(C& c) //throws() to ensure no exceptions ? { c.vx = 0; c.vy = 0; } Thanks in advance

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• How to reduce the Number of threads running at instance in jetty server ?

  - by Thirst for Excellence

  i would like to reduce the live threads on server to reduce the bandwidth consumption for data(data pull while application launching time) transfer from my application to clients in my application. i did setting like is this setting enough to reduce the bandwidth consumption on jetty server ? Please help me any one 1) in Jetty.xml: <Set name="ThreadPool"> <New class="org.eclipse.jetty.util.thread.QueuedThreadPool"> <name="minThreads"> 1 > <Set name="maxThreads" value=50> 2: services-config.xml channel-definition id="my-longpolling-amf" class="mx.messaging.channels.AMFChannel" endpoint url="http://MyIp:8400/blazeds/messagebroker/amflongpolling" class="flex.messaging.endpoints.AMFEndpoint" properties <polling-enabled>true</polling-enabled> <polling-interval-seconds>1</polling-interval-seconds> <wait-interval-millis>60000</wait-interval-millis> <client-wait-interval-millis>1</client-wait-interval-millis> <max-waiting-poll-requests>50</max-waiting-poll-requests> </properties> </channel-definition>

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• Call a non member function on an instance before is constructed.

  - by Tom

  Hi everyone. I'm writing a class, and this doubt came up. Is this undef. behaviour? On the other hand, I'm not sure its recommended, or if its a good practice. Is it one if I ensure no exceptions to be thrown in the init function? //c.h class C{ float vx,vy; friend void init(C& c); public: C(); }; //c.cpp C::C() { init(*this); } void init(C& c) //throws() to ensure no exceptions ? { c.vx = 0; c.vy = 0; } Thanks in advance

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• How to enforce jsf to create new instance of bean instead of throwing NullPointerException?

  - by Roman

  I'm almost sure that I do something wrong and thus the question's title is a bit incorrect. I have a form with several fields for creating a new User-objects (fields like login, password, birthday etc). And I have 2 buttons - Cancel and Create. I didn't finish Create yet :) , but when I press Cancel I see NullPointerException. Here is simplified code: <f:view> <h:form> <h:panelGroup layout="block"> <h:inputText id="add_login" value="#{userSupport.user.login}"/> <h:inputSecret id="add_password" value="#{userSupport.user.password}"/> <h:inputText id="add_name" value="#{userSupport.user.name}"/> <h:inputText id="add_surname" value="#{userSupport.user.surname}"/> <h:commandButton value="Cancel" action="cancel"/> </h:panelGroup> </h:form> </f:view> UserSupport class has field user with getter and setter and some other methods. It's a Spring bean with Session scope. When I press cancel, I see NPE because jsf tries to save values from inputs in user-object, but user-object is null. What is the correct way of doing this?

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• Shuffle array variables in a pre-specified order, without using extra memory of "size of input array"

  - by Eternal Learner

  Input : A[4] = {0,4,-1,1000} - Actual Array P[4] = {1,0,3,2} - Order to be reshuffled Output: A[4] = {4,0,1000,-1} Condition : Don't use an additional array as memory. Can use an extra variable or two. Problem : I have the below program in C++, but this fails for certain inputs of array P. #include<iostream> using namespace std; void swap(int *a_r,int *r) { int temp = *r; *r = *a_r; *a_r = temp; } int main() { int A[4] = {0,4,-1,1000}; int P[4] = {3,0,1,2}; int value = A[0] , dest = P[0]; for(int i=0; i<4;i++) { swap(&A[dest],&value); dest = P[dest]; } for(int i=0;i<4;i++) cout<<A[i]<<" "; }

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• How to address thread-safety of service data used for maintaining static local variables in C++?

  - by sharptooth

  Consider the following scenario. We have a C++ function with a static local variable: void function() { static int variable = obtain(); //blahblablah } the function needs to be called from multiple threads concurrently, so we add a critical section to avoid concurrent access to the static local: void functionThreadSafe() { CriticalSectionLockClass lock( criticalSection ); static int variable = obtain(); //blahblablah } but will this be enough? I mean there's some magic that makes the variable being initialized no more than once. So there's some service data maintained by the runtime that indicates whether each static local has already been initialized. Will the critical section in the above code protect that service data as well? Is any extra protection required for this scenario?

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• Declare variables that depend on unknown type in template functions.

  - by rem

  Suppose I'm writing a template function foo that has type parameter T. It gets an object of type T that must have method bar(). And inside foo I want to create a vector of objects of type returned by bar. In GNU C++ I can write something like that: template<typename T> void foo(T x) { std::vector<__typeof(x.bar())> v; v.push_back(x.bar()); v.push_back(x.bar()); v.push_back(x.bar()); std::cout << v.size() << std::endl; } How to do the same thing in Microsoft Visual C++? Is there some way to write this code that works in both GNU C++ and Visual C++?

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• Statically linked libraries not running code inside to setup static variables.

  - by MJD

  In a c++ project I am working on, I have a simple c++ file that needs to run some code at the beginning of the program execution. This file is linked into a static library, which is then linked into the main program. I have similar code in other files running fine, that looks something like: bool ____nonexistent_value = executeAction(); However, it does not work inside this file unless I make use of a function implemented in this file. It does work if the library is compiled as a shared library. I'd prefer to link this statically as the library is only a convenience as the file is in a different directory.

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• How to convert a child instance to parent class and the reverse in PHP?

  - by symfony

  $child_instance = (childClass)$parent_instance; $parent_instance = (parentClass)$child_instance; Or is it possible?

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• A reader method that returns the value of an instance variable and then resets it to nil

  - by snl

  Is there a shorter (and cleaner) way to write the following reader method: class Foo attr_writer :bar def bar return_value = @bar self.bar = nil return_value end end Here's some output on the console to show what it does: >> foo = Foo.new => #<Foo:0x1010e9cf8> >> foo.bar => nil >> foo.bar = "ok" => "ok" >> foo.bar => "ok" >> foo.bar => nil

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• C# Add class instance with internal timer to a static List, is it safe?

  - by CodeMongo

  My program has a static list of type classA. ClassA implements a threading timer that executes a task. The list may contain as many instances of classA as desired. Is this technique causing threading issues where the class instances can block each other? It that is the case how can I solve the that problem. ex: static List<MyClassType> list=null; void static Main() { list = new List<MyClassType>(); var a = new MyClassType(); var b = new MyClassType(); list.Add(a); list.Add(b); Console.ReadKey(); } a and b will execute theire internal task based on the timer.Is it s bsd technique? Why?

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• how would i run amazon instance from a shared hosting?

  - by IraqHussain

  linux os.can that be done with php?

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• Why is my prototype function not returning the property of the instance?

  - by Pydroid

  Hi, I have a simple object in Javascript. function myClass(x,y) { this.x = x; this.y = y; } and a prototype function myClass.prototype.myfunction = function() { console.log(this.x); } and in my main script, var x = 2; var y = 4; myinstance = new myClass(x,y); myinstance.myfunction(); Instead of receiving x, I get undefined instead. Why is that?

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• How do you keep the value of global variables (namely a struct variable) between postbacks?

  - by user3702304

  I'm new to this and have already searched for this with not much luck :( Lets say I have defined a struct array globally and filled the array with data on an Ajax ModalPopupExtender. I then have a ddl_SelectedIndexChanged event that does a postback and seems to recycle my array. Is there a way to fire the ddl_SelectedIndexChanged event to perform some code without doing a postback? Or is there an easy way to make the array of type struct retain it's values? (I am creating a website btw) Thanks in advance...

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• What is the point declaring variables at the end of class?

  - by serhio

  I saw multiple examples in MSDN that uses to declare the internal fields at the end of the class. What is the point? I find this a little embarrassing, because each time Visual Studio adds a method it adds it to the end of the class, so there is need every time to move it... class A { public A(){} // Methods, Properties, etc ... private string name; } class A { private string name; public A(){} // Methods, Properties, etc ... }

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• Variables Expired before Asp.net Membership provider automatically logout .

  - by Bendar

  I have a microsoft membership provider. in my application I'm using the variable which saving in cookie (tried session). The problem what I have: my variable expired before a authentication automatically logout. How can I set the time of membership provider automatic logout and expiring variable after 30 mins for example. Or how can I create a new server variable? Or maybe you suggest me better approach? Thank you

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