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  • How to invoke static method in C#4.0 with dynamic type?

    - by Morgan Cheng
    In C#4.0, we have dynamic type, but how to invoke static method of dynamic type object? Below code will generate exception at run time. class Foo { public static int Sum(int x, int y) { return x + y; } } class Program { static void Main(string[] args) { dynamic d = new Foo(); Console.WriteLine(d.Sum(1, 3)); } } IMHO, dynamic is invented to bridge C# and other programming language. There is some other language (e.g. Java) allows to invoke static method through object instead of type. BTW, The introduction of C#4.0 is not so impressive compared to C#3.0.

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  • Specializing a template on a lambda in C++0x

    - by Tony A.
    I've written a traits class that lets me extract information about the arguments and type of a function or function object in C++0x (tested with gcc 4.5.0). The general case handles function objects: template <typename F> struct function_traits { template <typename R, typename... A> struct _internal { }; template <typename R, typename... A> struct _internal<R (F::*)(A...)> { // ... }; typedef typename _internal<decltype(&F::operator())>::<<nested types go here>>; }; Then I have a specialization for plain functions at global scope: template <typename R, typename... A> struct function_traits<R (*)(A...)> { // ... }; This works fine, I can pass a function into the template or a function object and it works properly: template <typename F> void foo(F f) { typename function_traits<F>::whatever ...; } int f(int x) { ... } foo(f); What if, instead of passing a function or function object into foo, I want to pass a lambda expression? foo([](int x) { ... }); The problem here is that neither specialization of function_traits<> applies. The C++0x draft says that the type of the expression is a "unique, unnamed, non-union class type". Demangling the result of calling typeid(...).name() on the expression gives me what appears to be gcc's internal naming convention for the lambda, main::{lambda(int)#1}, not something that syntactically represents a C++ typename. In short, is there anything I can put into the template here: template <typename R, typename... A> struct function_traits<????> { ... } that will allow this traits class to accept a lambda expression?

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  • Always require a plugin to be loaded

    - by axon
    I am writing an application with RequireJS and Knockout JS. The application includes an extension to knockout that adds ko.protectedObservable to the main knockout object. I would like this to always be available on the require'd knockout object, and not only when I specify it in the dependencies. I could concat the files together, but that seems that it should be unnecessary. Additionally, I can put knockout-protectedObservable as a dependency for knockout in the requirejs shim configuration, but that just leads to a circular dependency and it all fails to load. Edit: I've solved me issue, but seems hacky, is there a better way? -- Main.html <script type="text/javascript" src="require.js"></script> <script type="text/javascript"> require(['knockout'], function(ko) { require(['knockout-protectedObservable']); }); </script> -- knockout-protectedObservable.js define(['knockout'], function(ko) { ko.protectedObservable = { ... }; });

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  • Error while coping datacolumn with data from one table to another .

    - by Harikrishna
    I have one Datatable like DataTable addressAndPhones; And there are four columns name,address,phoneno,and other details and I only want two columns Name and address from that so I do for that is DataTable addressAndPhones2; addressAndPhones2.Columns.Add(new DataColumn(addressAndPhones.Columns["name"].ColumnName)); addressAndPhones2.Columns.Add(new DataColumn(addressAndPhones.Columns["address"].ColumnName)); But it gives me error so how can I copy fix no of columns data from one table to another table ? ERROR :Object reference not set to an instance of an object.

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  • c# how to set up and use session state from preinit

    - by Praesagus
    OK so to set and read variables from the current session String Myvar =(string) System.Web.HttpContext.Current.Session[“MyVariable”] To set System.Web.HttpContext.Current.Session[“MyVariable”] = “NewValue” I can do neither, I get a System.NullReferenceException: Object reference not set to an instance of an object. from System.Web.HttpContext.Current.Session. In my web.config I have <sessionState mode="StateServer" stateConnectionString="tcpip=127.0.0.1:42424" cookieless="false" timeout="20"> </sessionState> I have read a dozen articles on the the necessity of IHttpHandler and an IRequiresSessionState interface. I think the issue may be caused because I am requesting this information in Page_PreInit. I found a solution in a stack overflow article but I don't seem be using it properly to actually make this go. I am not sure what I am missing. Thanks in advance.

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  • Scala methods ending in _=

    - by Alexey Romanov
    I seem to remember Scala treating methods ending in _= specially, so something like this: object X { var x: Int = 0; def y_=(n : Int) { x = n }} X.y = 1 should call X.y_=(1). However, in 2.8.0 RC1, I get an error message: <console>:6: error: value y is not a member of object X X.y = 1 ^ Interestingly, just trying to call the method without parentheses fails as well: scala> X.y_= 1 <console>:1: error: ';' expected but integer literal found. X.y_= 1 ^ Am I misremembering something which does actually exist or did I just invent it out of whole cloth?

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  • Does isolation frameworks (Moq, RhinoMock, etc) lead to test overspecification?

    - by Marius
    In Osherove's great book "The Art of Unit Testing" one of the test anti-patterns is over-specification which is basically the same as testing the internal state of the object instead of some expected output. To my experience, using Isolation frameworks can cause the same unwanted side effects as testing internal behavior because one tends to only implement the behavior necessary to make your stub interact with the object under test. Now if your implementation changes later on (but the contract remains the same), your test will suddenly break because you are expecting some data from the stub which was not implemented. So what do you think is the best approach to counter this? 1) Implement your stubs/mocks fully, this has the negative side-effect of potentially making your test less readable and also specifying more than necessary to make your test pass. 2) Favor manual, fully implemented fakes. 3) Implement your stubs/fakes so that they make your test just pass, and then deal with the brittleness that this might introduce.

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  • Is there any method in Cocoa that helps iterating through all NSColor values(R,G,B only, alpha not t

    - by krasnyk
    You may ask why do I need it? I have to detect all white objects at the B/W image. I'm coloring each object and taking its rect. In order fill each object with different color I would be very happy to use a function that can for a given color gimme a next one or so. In Qt there is a nice one that is called nextColor or so, returns the integer representing the next color(which can be easily translated to RGB). Does Cocoa have sth like that?

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  • Coldfusion CFC creation taking a variable amout of time to execute.

    - by Bazza
    I've been doing some logging of object creation times in our open account process in production. Periodically, initializing an object would take way longer than expected. By initializing I mean calling it's init() and passing a couple of arguments that may be simple variables or objects. e.g. <cfset validateObj = createObject("component", "compExample").init( productionMode = VARIABLES.productionMode, ipWhiteListed = isWhiteListed, ipLocatorObj = VARIABLES.ipLocatorObj ) /> Thats all that happens in init() methods. Generally the execution time would be 0ms, but at random times I might get 3 or 3.5 seconds. This is not specific to one particular server or to our generally busy period. It appears to be quite random. One thought was that these templates were being evicted from our template cache as they are not especially frequently used, although I checked cfstat on a number of servers and the max CP/Sec is -1. Running CF 8,0,1 Has anybody else ever come across this?

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  • Use SQL query to populate property in nHibernate mapping file

    - by brainimus
    I have an object which contains a property that is the result of an SQL statement. How do I add the SQL statement to my nHibernate mapping file? Example Object: public class Library{ public int BookCount { get; set; } } Example Mapping File: <hibernate-mapping> <class name="Library" table="Libraries"> <property name="BookCount" type="int"> <- This is where I want the SQL query to populate the value. -> </class> </hibernate-mapping> Example SQL Query: SELECT COUNT(*) FROM BOOKS WHERE BOOKS.LIBRARY_ID = LIBRARIES.ID

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  • Why can't I read session variables

    - by Marty Goetz
    I have a c# .net web application. I create session variables but when I try to read them after I leave the page that they were created from I can't. Created on page 1 Session["UserName"] = "WhatEver"; Then I do Response.Redirect("~/whatever.aspx"); and try to read to read the session variable in the Page_Load method of the new page string userName = Session["UserName"].ToString(); I receive "Object reference not set to an instance of an object." Why am I receiving this error and what can I do to fix the problem? I would greatly appreciate any help anyone can give me.

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  • ADO.NET - DataRead Error

    - by user560706
    Hi, I am trying to display data from a column in my database onto my rich textbox, but I am getting mixed up between DataSet and DataReader - I know the majority of the code below is correct, I just get two lines containing errors, and I'm not sure why: // Create a connection string string ConnectionString = ("Provider=Microsoft.ACE.OLEDB.12.0;Data Source= C:\\Documents and Settings\\Harley\\Desktop\\Test.accdb"); string SQL = "SELECT * FROM Paragraph"; // create a connection object SqlConnection conn = new SqlConnection(ConnectionString); // Create a command object SqlCommand cmd = new SqlCommand(SQL, conn); conn.Open(); DataTable dt = new DataTable(); da.Fill(dt); //ERROR // Call ExecuteReader to return a DataReader SqlDataReader reader = cmd.ExecuteReader(); foreach(DataRow reader in dsRtn) //ERROR { richTextBox = richTextBox.Text + reader[0].ToString(); } //Release resources reader.Close(); conn.Close(); }

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  • Can I make PDOStatement->fetchObject not use non-member variables?

    - by threendib
    Lets say I have a class like this: Class User { var $id var $name; } And I run a query using PDO in php like so: $stm = $db->prepare('select * from users where id = :id'); $r = $stm->execute(array(':id' => $id)); $user = $r->fetchObject('User'); If I vardump my user object it has all kinds of other fields in it that I have not defined in the User class. Obviously I could make my query specific so that it only gives me back the fields I need/want. But if I don't want to do that is there any way to make this work the way I want it to? I like the idea of fetchObject, because it's one line of code to create this object and set member variables for me. I just don't want it to set variables I haven't defined in my class.

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  • Simple Scala syntax - trying to define "==" operator - what am I missing?

    - by Alex R
    While experimenting with some stuff on the REPL, I got to a point where I needed something like this: scala class A(x:Int) { println(x); def ==(a:A) : Boolean = { this.x == a.x; } } Just a simple class with an "==" operator. Why doesn't it work??? Here's the result: :10: error: type mismatch; found : A required: ?{val x: ?} Note that implicit conversions are not applicable because they are ambiguous: both method any2ArrowAssoc in object Predef of type [A](x: A)ArrowAssoc[A] and method any2Ensuring in object Predef of type [A](x: A)Ensuring[A] are possible conversion functions from A to ?{val x: ?} class A(x:Int) { println(x); def ==(a:A) : Boolean = { this.x == a.x; } } ^ This is scala 2.8 RC1. Thanks

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  • Writing secure java code with RMI

    - by jtnire
    Hi Everyone, This may seem like a very broad question, but any help is appreciated. I have a client/server solution written in java which uses the Cajo project (which uses RMI). I just want to try and make my solution as secure as possible, given the sensitive data that will be transferred between server and client. So far, my ideas are to make all my classes "final" as well as throw a "non-serializable" exception for all my classes in the server (except for the object bound in the RMI registry, and any objects that actually do need to be transferred of course). Can anyone think of any other ideas? I know that someone could write a malicious client - this isn't hard to do as you can find out the remote object's API using reflection. However is there anything I can do to protect a malicious client access classes/objects within the server that they are not supposed to access? Many Thanks

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  • How to display a tree of objects in a JTree?

    - by paul
    Imagine a collection of objects such as World, Country, Region and City. World contains a list of Country objects, Country contains a list of Region objects etc. I would like to represent this structure in a JTree and be able to add, remove and move objects around the tree. Can I easily create a TableModel from this structure? World would be the root object and I would need to perform some object-specific rendering. Any one know of an appropriate tutorial?

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  • Looking for design patterns to isolate framework layers from each other

    - by T Reddy
    Hi, I'm wondering if anyone has any experience in "isolating" framework objects from each other (Spring, Hibernate, Struts). I'm beginning to see design "problems" where an object from one framework gets used in another object from a different framework. My fear is we're creating tightly coupled objects. For instance, I have an application where we have a DynaActionForm with several attributes...one of which is a POJO generated by the Hibernate Tools. This POJO gets used everywhere...the JSP populates data to it, the Struts Action sends it down to a Service Layer, the DAO will persist it...ack! Now, imagine that someone decides to do a little refactoring on that POJO...so that means the JSP, Action, Service, DAO all needs to be updated...which is kind of painful...There has got to be a better way?! There's a book called Core J2EE Patterns: Best Practices and Design Strategies (2nd Edition)...is this worth a look? I don't believe it touches on any specific frameworks, but it looks like it might give some insight on how to properly layer the application... Thanks!

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  • How to make Event visible?

    - by eflles
    Inside a Silverlight library project I have a public event, which is not visible for other classes. How can I make the event visible? When I try the following code, I can not locate the event in the "ReceivingClass". .dll - file: Public Class MyClass Public Event MyEvent(ByVal sender As Object, ByVal e As EventArgs) Public Sub OnStart() RaiseEvent MyEvent(Me, new EventArgs) End Sub End Class Silverlight app: Imports MyClass Public Class ReceivingClass Public Sub New() Dim myClass As new MyClass AddHandler myClass.MyEvent, AddressOf Me.EventHandler End Sub Private Sub EventHandler(ByVal sender As Object, ByVal e As EventArgs) 'Handle Event End Sub End Class

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  • Connecting data to a GUI - OOP

    - by tau
    I have an application with several graphs and tables on it. I worked fast and just made classes like Graph and Table that each contained a request object (pseudo-code): class Graph { private request; public function setDateRange(dateRange) { request.setDateRange(dateRange); } public function refresh() { request.getData(function() { //refresh the display }); } } Upon a GUI event (say, someone changes the date range dropdown), I'd just call the setters on the Graph instance and then refresh it. Well, when I added other GUI elements like tables and whatnot, they all basically had similar methods (setDateRange and other things common to the request). What are some more elegant OOP ways of doing this? The application is very simple and I don't want to over-architect it, but I also don't want to have a bunch of classes with basically the same methods that are just routing to a request object. I also don't want to set up each GUI class as inheriting from the request class, but I'm open to any ideas really.

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  • override the operator overloading in C++ ?

    - by stdnoit
    helo guys i have class call Complex I did operator overloading like such Complex c = a + b; // where a and b are object of Complex class which basically is operator+(Complex& that); but I dont know how to say for example double c = a + 10; //where a is object of Complex class but 10 is integer / double I did define typecasting for a to be double get my IDE says that there are too many operands + and it somehow complains for not being able to "understand" the + it has to be in this format though double c = a + 10; thanks

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  • Calling this[int index] via reflection

    - by tkutter
    I try to implement a reflection-based late-bound library to Microsoft Office. The properties and methods of the Offce COM objects are called the following way: Type type = Type.GetTypeFromProgID("Word.Application"); object comObject = Activator.CreateInstance(type); type.InvokeMember(<METHOD NAME>, <BINDING FLAGS>, null, comObject, new object[] { <PARAMS>}); InvokeMember is the only possible way because Type.GetMethod / GetProperty works improperly with the COM objects. Methods and properties can be called using InvokeMember but now I have to solve the following problem: Method in the office-interop wrapper: Excel.Workbooks wb = excel.Workbooks; Excel.Workbook firstWb = wb[0]; respectively foreach(Excel.Workbook w in excel.Workbooks) // doSmth. How can I call the this[int index] operator of Excel.Workbooks via reflection?

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