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  • Best practices for using memcached in Rails?

    - by Matt
    Hello everybody, as database transcations in our app are getting more and more time consuming, we have started to use memcached to reduce the amount of queries passed to MySQL. All in all, it works fine and really saves a lot of time. But as caching was "silently appearing" as a workaround to give the app more juice, a lot of our models now contain code like this: def self.all_cached Rails.cache.fetch('object_name') { find( :all, :include => [associations]) } end This is getting more and more a pain as filling and flushing the cache happens in several classes accross the application. Now, I was wondering if there was a better way to abstract memcached logic to make it more powerful and easy to use across all needed models? I was thinking about having some kind of memcached-module which is included in all needed modules. But before playing around, I thought: Let's ask experts first :-) Thanks Matt

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  • How do I implement a custom Brush in WPF?

    - by MojoFilter
    Where can I find out enough info about how Brushes work to implement my own System.Windows.Media.Brush? I can handle all of the freezable baggage, but it's not really obvious what I need to override to get it to work. Yeah, so I didn't mean that I want to use a predefined brush. I want to extend System.Windows.Media.Brush, which is an abstract class. This is all purely for my own edification. I'm not even sure what kind of brush I could make. I was just trying to learn how brushes work. As in: public AwesomeBrush : Brush { protected override Freezable CreateInstanceCore() { return new AwesomeBrush(); } ... // concrete brush stuff }

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  • Specifying distinct sequence per table in Hibernate on subclasses

    - by gutch
    Is there a way to specify distinct sequences for each table in Hibernate, if the ID is defined on a mapped superclass? All entities in our application extend a superclass called DataObject like this: @MappedSuperclass public abstract class DataObject implements Serializable { @Id @GeneratedValue(strategy = GenerationType.SEQUENCE) @Column(name = "id") private int id; } @Entity @Table(name = "entity_a") public class EntityA extends DataObject { ... } @Entity @Table(name = "entity_b") public class EntityB extends DataObject { ... } This causes all entities to use a shared sequence, the default hibernate_sequence. What I would like to do is use a separate sequence for each entity, for example entity_a_sequence and entity_b_sequence in the example above. If the ID were specified on the subclasses then I could use the @SequenceGenerator annotation to specify a sequence for each entity, but in this case the ID is on the superclass. Given that ID is in the superclass, is there a way I can use a separate sequence for each entity — and if so, how? (We are using PostgreSQL 8.3, in case that's relevant)

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  • ActionScript: Type coercion problem with BlazeDS/AMF and class interfaces

    - by mike
    Hi, I've got a problem with type coercion in a Java/Hibernate/BlazeDS/Flex-Setup. First of all, my classes look like this: --- JAVA --- Interface I (Abstract) Class A implements I Class B extends A --- ActionScript --- Interface I Class A implements I Class B extends A I got RemoteClass-Meta-Tags in all ActionScript-Classes/Interfaces I, A and B. Package structure and Class/Interface names are exactly the same. Now here's the problem: My Java Service successfully retrieves objects of class B from my database via Hibernate. I got another class C which has a member property of interface type I, so it should be possible to assign an object of type B. But for some reason i get the following error message: TypeError: Error #1034: cannot convert Object@28b44a89 to package.name.I I checked the Java object type in the service and it is of type B and seems to be totally fine. Why can't the object of type B be assigned to a member variable of type I? This is driving me nuts. Thanks in advance.

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  • ASP.NET MVC IoC usability

    - by Andrew Florko
    Hello everybody, How often do you use IoC for controllers/DAL in real projects? IoC allows to abstract application from concrete implementation with additional layer of interfaces that should be implemented. But how often concrete implementation changes? Should we really have to do job twice adding method to interface then the implementation if implementation hardly will ever be changed? I took part in about 10 asp.net projects and DAL (ORM-like and not) was never rewritten completely. Watching lots of videos I clearly understand that IoC "is cool" and the really nice way to program, but does it really needed?

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  • Is it possible to overwrite a static method in parent class?

    - by MartinDenny2069
    I have a static method defined in a base class, I want to overwrite this method in its child class, is it possible? I tried this but it did not work as I expected. When I created an instance of class B and invoke its callMe() method, the static foo() method in class A is invoked. public abstract class A { public static void foo() { System.out.println("I am base class"); } public void callMe() { foo(); } } Public class B { public static void foo() { System.out.println("I am child class"); } }

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  • Specification, modeling and programming are principially the same, right?

    - by Gabriel Šcerbák
    In formal specifications based on abstract algebraic types and equational theory you use formulas of equational theory to specify theory. System which will satisfy those constraints is called in formal logic a model. Modeling is process of creating a model, which abstracts of some aspects, which are unnecessary details for a specific case. So concrete system has to adhere to created model in observed aspects. Programming is a process of creating a program which will have specific behaviour - will perform specific algorithms - and programming languages through different paradigms enable us to think in a certain specific way, which abstracts of some details, usually machine specific ones. So could we be doing all those things at the same time, because they are principially the same? Is declarative programming the nearest attempt to do that? Could we use some sort f programming languages which will be good for programming as well as for modeling and specification?

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  • Good articles to read on SSL and HTTPS?

    - by Igor Romanov
    I had a problem with accepting invalid SSL certificate in my iPhone program. That problem is solved now, however I came to understanding that I have very abstract idea on how exactly the whole thing is working: how web browser is verifying that received certificate is really for host it communicates to and not faked by same party in the middle? if browser talks to some 3rd party (CA?) to do certificate check? and many other questions... Would someone please recommend good source of information with in-depth enough description of how all parts click together?

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  • identifying the type

    - by Gokul
    Hi, In my application, there is a inheritance hierarchy in which only the classes that are at the end of the inheritance chain are non-abstract classes. Also there is some usage of boost::variant. I want to write a function which takes a pointer and a Type and says whether the object belongs to that type. For example template< typename Type, bool TypeisAbstract, typename ptrType > bool checkType( ptrType* t) { return ( typeid(*t) == typeid(Type) ); } template< typename Type, typename ptrType > bool checkType<Type, true, ptrType>( ptrType* t) { return ( dynamic_cast<Type*>(t) != NULL ); } Now if there is a boost variant, i want to find out whether the boost variant stores that particular type. Can someone help me with that? Thanks, Gokul.

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  • Scala - Enumeration vs. Case-Classes

    - by tzofia
    I've created akka actor called LogActor. The LogActors's receive method handling messages from other actors and logging them to the specified log level. I can distinguish between the different levels in 2 ways. The first one: import LogLevel._ object LogLevel extends Enumeration { type LogLevel = Value val Error, Warning, Info, Debug = Value } case class LogMessage(level : LogLevel, msg : String) The second: (EDIT) abstract class LogMessage(msg : String) case class LogMessageError(msg : String) extends LogMessage(msg) case class LogMessageWarning(msg : String) extends LogMessage(msg) case class LogMessageInfo(msg : String) extends LogMessage(msg) case class LogMessageDebug(msg : String) extends LogMessage(msg) Which way is more efficient? does it take less time to match case class or to match enum value? (I read this question but there isn't any answer referring to the runtime issue)

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  • Django loaddata throws ValidationError: [u'Enter a valid date in YYYY-MM-DD format.'] on null=true f

    - by datakid
    When I run: django-admin.py loaddata ../data/library_authors.json the error is: ... ValidationError: [u'Enter a valid date in YYYY-MM-DD format.'] The model: class Writer(models.Model): first = models.CharField(u'First Name', max_length=30) other = models.CharField(u'Other Names', max_length=30, blank=True) last = models.CharField(u'Last Name', max_length=30) dob = models.DateField(u'Date of Birth', blank=True, null=True) class Meta: abstract = True ordering = ['last'] unique_together = ("first", "last") class Author(Writer): language = models.CharField(max_length=20, choices=LANGUAGES, blank=True) class Meta: verbose_name = 'Author' verbose_name_plural = 'Authors' Note that the dob DateField has blank=True, null=True The json file has structure: [ { "pk": 1, "model": "books.author", "fields": { "dob": "", "other": "", "last": "Carey", "language": "", "first": "Peter" } }, { "pk": 3, "model": "books.author", "fields": { "dob": "", "other": "", "last": "Brown", "language": "", "first": "Carter" } } ] The backing mysql database has the relevent date field in the relevant table set to NULL as default and Null? = YES. Any ideas on what I'm doing wrong or how I can get loaddata to accept null date values?

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  • Fastest method for SQL Server inserts, updates, selects from C# ASP.Net 2.0+

    - by Ian
    Hi All, long time listener, first time caller. I use SPs and this isn't an SP vs code-behind "Build your SQL command" question. I'm looking for a high-throughput method for a backend app that handles many small transactions. I use SQLDataReader for most of the returns since forward only works in most cases for me. I've seen it done many ways, and used most of them myself. Methods that define and accept the stored procedure parameters as parameters themselves and build using cmd.Parameters.Add (with or without specifying the DB value type and/or length) Assembling your SP params and their values into an array or hashtable, then passing to a more abstract method that parses the collection and then runs cmd.Parameters.Add Classes that represent tables, initializing the class upon need, setting the public properties that represent the table fields, and calling methods like Save, Load, etc I'm sure there are others I've seen but can't think of at the moment as well. I'm open to all suggestions.

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  • NHibernate with or without Repository

    - by Groo
    There are several similar questions on this matter, by I still haven't found enough reasons to decide which way to go. The real question is, is it reasonable to abstract the NHibernate using a Repository pattern, or not? It seems that the only reason behind abstracting it is to leave yourself an option to replace NHibernate with a different ORM if needed. But creating repositories and abstracting queries seems like adding yet another layer, and doing much of the plumbing by hand. One option is to use expose IQueryable<T> to the business layer and use LINQ, but from my experience LINQ support is still not fully implemented in NHibernate (queries simply don't always work as expected, and I hate spending time on debugging a framework). Although referencing NHibernate in my business layer hurts my eyes, it is supposed to be an abstraction of data access by itself, right? What are you opinions on this?

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  • jquery tabs with form help

    - by sico87
    Hello, I am implementing jQuery tabs on mysite, one of the tabs holds a form and this is my problem, the form is loaded in via ajax as it is used multiple time throughout the site. My issue is that when the form is submitted the page leaves the tabbed area, whereas I need to stay within the tabbed system. Below is the code I am using TABS HTML <div id="tabs"> <ul> <li><a href="#tabs-1">Active Categories</a></li> <li><a href="#tabs-2">De-activated Categories</a></li> <li><a href="<?=base_url();?>admin/addCategory">Add A New Category</a></li> </ul> FORM MARKUP <div id="contact_form"> <?php // open the form echo form_open(base_url().'admin/addCategory'); // categoryTitle echo form_label('Category Name', 'categoryTitle'); echo form_error('categoryTitle'); $data = array( 'name' => 'categoryTitle', 'id' => 'categoryTitle', 'value' => $categoryTitle, ); echo form_input($data); // categoryAbstract $data = array( 'name' => 'categoryAbstract', 'id' => 'categoryAbstract wysiwyg', 'value' => $categoryAbstract, ); echo form_label('Category Abstract', 'categoryAbstract'); echo form_error('categoryAbstract'); echo form_textarea($data); // categorySlug $data = array( 'name' => 'categorySlug', 'id' => 'categorySlug', 'value' => $categorySlug, ); echo form_label('Category Slug', 'categorySlug'); echo form_error('categorySlug'); echo form_input($data); // categoryIsSpecial /*$data = array( 'name' => 'categoryIsSpecial', 'id' => 'categoryIsSpecial', 'value' => '1', 'checked' => $checkedSpecial, ); echo form_label('Is Category Special?', 'categoryIsSpecial'); echo form_error('categoryIsSpecial'); echo form_checkbox($data);*/ // categoryOnline $data = array( 'name' => 'categoryOnline', 'id' => 'categoryOnline', 'value' => '1', 'checked' => $checkedOnline, ); echo form_label('Online?', 'categoryOnline'); echo form_checkbox($data); echo form_error('categoryOnline'); //hidden field check if we are adding or editing echo form_hidden('edit', $edit); echo form_hidden('categoryId', $categoryId); // categorySubmit $data = array('class' => 'submit', 'id' => 'submit', 'value'=>'Submit', 'name' => 'categorySubmit'); echo form_submit($data); echo form_close(); ?> </div> FORM PROCESS function saveCategory() { $data = array(); // we need to set the what element the form errors get displayed in $this->form_validation->set_error_delimiters('<div class="formError">', '</div>'); // we need to estabilsh some rules so the form can be submitted without error, // or if there is error then the form needs show errors. $config = array( array( 'field' => 'categoryTitle', 'label' => 'Category title', 'rules' => 'required|trim|max_length[25]|xss_clean' ), array( 'field' => 'categoryAbstract', 'label' => 'Category abstract', 'rules' => 'required|trim|max_length[150]|xss_clean' ), array( 'field' => 'categorySlug', 'label' => 'Category slug', 'rules' => 'required|trim|alpha|max_length[25]|xss_clean' ), /*array( 'field' => 'categoryIsSpecial', 'label' => 'Special category', 'rules' => 'trim|xss_clean' ),*/ array( 'field' => 'categoryOnline', 'label' => 'Category online', 'rules' => 'trim|xss_clean' ) ); $this->form_validation->set_rules($config); // with the validation rules set we can no run the validation rules over the form // if any the validation returns false then the error messages will be returned to the view // in the delimiters that we set further up the page. if($this->form_validation->run() == FALSE) { // we should reload the form $this->load->view('admin/add_category'); } }

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  • VB to C# conversion incongruency with lambdas

    - by Jason
    I have a bit of code that I have been tasked with converting to C# from VB. A snippet of mine seems like it cannot be converted from one to the other, and if so, I just don't know how to do it and am getting a little frustrated. Here's some background: OrderForm is an abstract class, inherited by Invoice (and also PurchaseOrder). The following VB snippet works correctly: Dim Invs As List(Of OrderForm) = GetForms(theOrder.OrderID) .... Dim inv As Invoice = Invs.Find( Function(someInv As Invoice) thePO.SubPONumber = someInv.SubInvoiceNumber) In C#, the best I came to converting this is: List<OrderForm> Invs = GetForms(theOrder.OrderID); .... Invoice inv = Invs.Find( (Invoice someInv) => thePO.SubPONumber == someInv.SubInvoiceNumber); However, I get the following error when I do this: Cannot convert lambda expression to delegate type 'System.Predicate' because the parameter types do not match the delegate parameter types Is there any way to fix this without restructuring my whole codebase?

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  • Is testability alone justification for dependency injection?

    - by fearofawhackplanet
    The advantages of DI, as far as I am aware, are: Reduced Dependencies More Reusable Code More Testable Code More Readable Code Say I have a repository, OrderRepository, which acts as a repository for an Order object generated through a Linq to Sql dbml. I can't make my orders repository generic as it performs mapping between the Linq Order entity and my own Order POCO domain class. Since the OrderRepository by necessity is dependent on a specific Linq to Sql DataContext, parameter passing of the DataContext can't really be said to make the code reuseable or reduce dependencies in any meaningful way. It also makes the code harder to read, as to instantiate the repository I now need to write new OrdersRepository(new MyLinqDataContext()) which additionally is contrary to the main purpose of the repository, that being to abstract/hide the existence of the DataContext from consuming code. So in general I think this would be a pretty horrible design, but it would give the benefit of facilitating unit testing. Is this enough justification? Or is there a third way? I'd be very interested in hearing opinions.

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  • extend web server to serve static files

    - by Turtle
    Hello, I want to extend a web server which is only able to handle RPC handling now. The web server is written in C#. It provides a abstract handler function like following: public string owsHandler(string request, string path, string param, OSHttpRequest httpRequest, OSHttpResponse httpResponse) And I wrote following code to handle image files: Bitmap queryImg = new Bitmap(path); System.IO.MemoryStream stream = new System.IO.MemoryStream(); queryImg.Save(stream, System.Drawing.Imaging.ImageFormat.Bmp); queryImg.Dispose(); byte[] byteImage = stream.ToArray(); stream.Dispose(); return Convert.ToBase64String(byteImage); And I test it in the browser, the image is returned but the image dimension info is missed. Shall I add something more to the code? Or is any general way to server static files? I do not want to serve it in a ASP.net server. Thanks

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  • Programmatically access document properties

    - by ngm
    Is there a way in which I can programmatically access the document properties of a Word 2007 document? I am open to using any language for this, but ideally it might be via a PowerShell script. My overall aim is to traverse the documents somewhere on a filesystem, parse some document properties from these documents, and then collate all of these properties back together into a new Word document. (I essentially want to automatically create a document which is a list of all documents beneath a certain folder of the filesystem; and this list would contain such things as the Title, Abstract and Author document properties; the CreateDate field; etc. for each document)

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  • Self-type mismatch in Scala

    - by Alexey Romanov
    Given this: abstract class ViewPresenterPair { type V <: View type P <: Presenter trait View {self: V => val presenter: P } trait Presenter {self: P => var view: V } } I am trying to define an implementation in this way: case class SensorViewPresenter[T] extends ViewPresenterPair { type V = SensorView[T] type P = SensorPresenter[T] trait SensorView[T] extends View { } class SensorViewImpl[T](val presenter: P) extends SensorView[T] { presenter.view = this } class SensorPresenter[T] extends Presenter { var view: V } } Which gives me the following errors: error: illegal inheritance; self-type SensorViewPresenter.this.SensorView[T] does not conform to SensorViewPresenter.this.View's selftype SensorViewPresenter.this.V trait SensorView[T] extends View { ^ <console>:13: error: type mismatch; found : SensorViewPresenter.this.SensorViewImpl[T] required: SensorViewPresenter.this.V presenter.view = this ^ <console>:16: error: illegal inheritance; self-type SensorViewPresenter.this.SensorPresenter[T] does not conform to SensorViewPresenter.this.Presenter's selftype SensorViewPresenter.this.P class SensorPresenter[T] extends Presenter { ^ I don't understand why. After all, V is just an alias for SensorView[T], and the paths are the same, so how can it not conform?

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  • Why is the base() constructor not necessary?

    - by Earlz
    Hello, I have a class structure like abstract class Animal { public Animal(){ //init stuff.. } } class Cat : Animal { public Cat(bool is_keyboard) : base() //NOTE here { //other init stuff } } Now then, look at the noted line. If you remove : base() then it will compile without an error. Why is this? Is there a way to disable this behavior? I have had multiple bugs now from forgetting the base() which I would have thought to be required on such a special thing as a constructor.

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  • Capturing USB Plug/Unplug events in Firemonkey

    - by radsdau
    [RAD Studio XE3 / C++] I have a FMX project running in Windows only at this stage, but I need to detect events when USB devices are connected and disconnected. I have a similar VCL app that can do this fine, but the Application-HookMainWindow is not exposed in FMX (only VCL). Is there an elegant way to handle this? Or do I have to hack some VCL stuff into my FMX app to make that work? I'd imagine I have to abstract it so I can support other platforms down the track. For the meantime though I need to get the Windows solution working. If the 'VCL hack' thing is required, how would I reference the vcl::Forms::Application from within my Fmx app? Cheers.

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  • how can I implement Comparable more than once?

    - by codeman73
    I'm upgrading some code to Java 5 and am clearly not understanding something with Generics. I have other classes which implement Comparable once, which I've been able to implement. But now I've got a class which, due to inheritance, ends up trying to implement Comparable for 2 types. Here's my situation: I've got the following classes/interfaces: interface Foo extends Comparable<Foo> interface Bar extends Comparable<Bar> abstract class BarDescription implements Bar class FooBar extends BarDescription implements Foo With this, I get the error 'interface Comparable cannot be implemented more than once with different arguments...' Why can't I have a compareTo(Foo foo) implemented in FooBar, and also a compareTo(Bar) implemented in BarDescription? Isn't this simply method overloading?

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  • Is there any graphics library in a higher level than OpenGL

    - by Turtle
    Hello, I am looking for a graphics library for 3D reconstruction research to develop my specific viewer based on some library. OpenGL seems in a low level and I have to remake the wheel everywhere. And I also tried VTK(visualization toolkit). However, it seems too abstract that I need to master many conceptions before I start. Is there any other graphics library? I prefer to program in python. So I would like the library has a python wrapper. I think something like O3D would be better. But O3D is for javascript and it seems that Google already stops the development.

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  • How do we, as a community, help encourage programming in public schools? (Or state Schools for the U

    - by NoMoreZealots
    PRIMARY MOTIVATION My office gets involved with the "First Robotics" competitions and one thing that lingers year to year is the students typically have no preparation for doing even simple programming as part of the public schools system. While the science classes provide some basic grasp of mechanical and electrical concepts, by in large computer programming gets no coverage from the curriculum. (This my be different in other areas of the country/world.) What makes it worse is there is only a short period of time you have to prepare the student's and help them design the robot. Talking to some professors from local colleges, it's a problem because you can't assume even the most basic understanding for freshman CS majors. Languages like Python, Lua and BASIC are simple enough for at least high school level students, if not younger. SCOPE So how do you get public schools to support a programming, at least to the level of "Try it in BASIC" examples that used to be at the end of a chapter in my Algebra book? At least enough to prepare them for event's such as the FIRST Robotic competitions. Which the primary objectives are to teach problem solving and team work, and to possible foster an interest in Math, Science and Engineering in general. (Not force feed to them, as some people her seem to be implying.) Edit: Why teach kids: (Since 2000 CS enrollment in US colleges has decreased by 70% while college enrollment has increased, this is a PROBLEM.) Saying there is no value in teaching someone programming in Jr./High school because they might think "they know programming." Is like saying there's no value in teaching High school science and physics, because they might decide they "know physics." Leading to abuse like: "I passed a high school physics class, I'm going to develop a Unified Quantum Gravitational Theory." Better Prepared students are better students. Instead it would allows college programs to raise the bar on the entry level courses, allowing students to be weeded out based on their understanding of more advanced material. Plus people who did poorly in that in topic in High school aren't as likely to say "I think there's money in computer's so I'll computer science." Plus if people take it in high school and decide THEN that it's not for them, it's better than them wasting their money to PAY a college to figure that out. The result is that people who take the degree are more likely to succeed and be there for the RIGHT reasons. (i.e. It's what they REALLY want to do. And that's REALLY the key to being good at anything.) Programming is like anything else, the more practice and genuine interest you have the better you get. If you start them later, they get less practice. The earlier give them the opportunity to start, the more practice they will get. All other things equal, the more practice the better the programmer.

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  • C# BinarySearch breaks when inheriting from something that implements IComparable<T>?

    - by Ender
    In .NET the BinarySearch algorithm (in Lists, Arrays, etc.) appears to fail if the items you are trying to search inherit from an IComparable instead of implementing it directly: List<B> foo = new List<B>(); // B inherits from A, which implements IComparable<A> foo.Add(new B()); foo.BinarySearch(new B()); // InvalidOperationException, "Failed to compare two elements in the array." Where: public abstract class A : IComparable<A> { public int x; public int CompareTo(A other) { return x.CompareTo(other.x); } } public class B : A {} Is there a way around this? Implementing CompareTo(B other) in class B doesn't seem to work.

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