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• Java DAO caching

  - by santiagobasulto

  I'm developing a medium Java app, and i'm facing a small problem due to my lack of experience. I've a custom DAO, which gets "Article" objects from the Database. I've the Article class, and the DAO has a method called getArticle(int id), this method returns an Article. The Article has a Category object, and I'm using lazy loading. So, when I request for an article's category (Article a = new Article(); a.getCategory();) the Article class gets the Category from the DAO and then returns it. I'm now thinking to cache it, so when I request multiple times to an article's category, the database is only queried one time. My question is: where should I put that cache? I can put it on the Article class (in the DTO), or I can put it on the DAO class. What do you say?

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• django admin site - filtering available objects for user

  - by JPG

  I have models that belong to some 'group' (Company class). I want to add users, who will also belong to a one group and should be able to edit/manage/add objects with membership in associated group. something like: class Company() class Something() company = ForeignKey(Company) user Microsoft_admin company = ForeignKey(Company) and this user should only see and edit objects belonging to associated Company in the Admin Interface. How to acomplish that?

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• Ruby core documentation quality

  - by karatedog

  I'm relatively new to Ruby and have limited time therefore I try out simple things. Recently I needed to create a file and because I'm lazy as hell, I run to Google. The result: File.open(local_filename, 'w') {|f| f.write(doc) } Shame on me, it is very straightforward, should have done it myself. Then I wanted to check what ruby magic the File class' methods offer or if there's any 'simplification' when invoking those methods, so I headed for the documentation here, and checked for the File class. 1.8.6 documentation presents me with "ftools.rb: Extra tools for the File class" under 'File' class, which is not what I'm looking for. 1.8.7 documentation seems OK for 'File' class, there are a plethora of methods. Except 'open'. 1.9 documentation finally shows me the 'open' method. And I had an almost same tour with Net::HTTP. Do I exaggerate when I think good old Turbo Pascal's 7.0 documentation was better organized than Ruby documentation is right now? Is there any other source for the uninitiated to collect knowledge? Or is it possible that I just tumbled into a documentation hole and the rest are super-brilliant-five-star organized? Thanks

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• Using group_by with fields_for and accepts_nested_attributes_for

  - by Derek

  I have a the following rails models: class Release < ActiveRecord::Base has_many :release_questionnaires, :dependent => :destroy accepts_nested_attributes_for :release_questionnaires ... end class class ReleaseQuestionnaire < ActiveRecord::Base belongs_to :release belongs_to :milestone ... end class In my view code, I have the following form. <% form_for @release, ... do |f| %> ... <table class="questionnaires"> <% f.fields_for :release_questionnaires, @release.release_questionnaires.sort_by{|ra| ra.questionnaire.name} do |builder| %> ... <% end %> </table> <% end %> This works and allows me to view and edit the questionnaires as desired. However, I have an additional requirement to break the questionnaires out into their own tables grouped by the milestone they are associated to, rather than in a single table. It appears as though the group_by method is design to accomplish this, but I cannot get it to work as desired inside the tag. It may be that I'm missing something obvious, as I am a beginner... Any help is appreciated.

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• overloading new/delete problem

  - by hidayat

  This is my scenario, Im trying to overload new and delete globally. I have written my allocator class in a file called allocator.h. And what I am trying to achieve is that if a file is including this header file, my version of new and delete should be used. So in a header file "allocator.h" i have declared the two functions extern void* operator new(std::size_t size); extern void operator delete(void *p, std::size_t size); I the same header file I have a class that does all the allocator stuff, class SmallObjAllocator { ... }; I want to call this class from the new and delete functions and I would like the class to be static, so I have done this: template<unsigned dummy> struct My_SmallObjectAllocatorImpl { static SmallObjAllocator myAlloc; }; template<unsigned dummy> SmallObjAllocator My_SmallObjectAllocatorImpl<dummy>::myAlloc(DEFAULT_CHUNK_SIZE, MAX_OBJ_SIZE); typedef My_SmallObjectAllocatorImpl<0> My_SmallObjectAllocator; and in the cpp file it looks like this: allocator.cc void* operator new(std::size_t size) { std::cout << "using my new" << std::endl; if(size > MAX_OBJ_SIZE) return malloc(size); else return My_SmallObjectAllocator::myAlloc.allocate(size); } void operator delete(void *p, std::size_t size) { if(size > MAX_OBJ_SIZE) free(p); else My_SmallObjectAllocator::myAlloc.deallocate(p, size); } The problem is when I try to call the constructor for the class SmallObjAllocator which is a static object. For some reason the compiler are calling my overloaded function new when initializing it. So it then tries to use My_SmallObjectAllocator::myAlloc.deallocate(p, size); which is not defined so the program crashes. So why are the compiler calling new when I define a static object? and how can I solve it?

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• Overwrite queryset which builds filter sidebar

  - by cw

  Hi, I'm writing a hockey database/manager. So I have the following models: class Team(models.Model): name = models.CharField(max_length=60) class Game(models.Model): home_team = models.ForeignKey(Team,related_name='home_team') away_team = models.ForeignKey(Team,related_name='away_team') class SeasonStats(models.Model): team = models.ForeignKey(Team) Ok, so my problem is the following. There are a lot of teams, but Stats are just managed for my Club. So if I use "list_display" in the admin backend, I'd like to modify/overwrite the queryset which builds the sidebar for filtering, to just display our home teams as a filter option. Is this somehow possible in Django? I already made a custom form like this class SeasonPlayerStatsAdminForm(forms.ModelForm): team = forms.ModelChoiceField(Team.objects.filter(club__home=True)) So now just the filtering is missing. Any ideas?

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• mysql eliminate responses under certain condition with join

  - by Dustin

  Forgive me if this is an easy question. I teach classes and want to be able to select those students who have taken one class, but not another class. I have two tables: lessons_slots which is the table for every class such as: -------------------- -ID name slots- -1 basics 10 - -2 advanced 10 - -3 basics 10 - --------------------- The other table is class_roll, which holds enrollment info, such as: -------------------- -sID classid firstname lastname- -1 1 Jo Schmo -2 1 Person Two ... -13 2 Jo Schmo --------------------- What I want to do, I select everyone who has not had the advanced class (for example). I've tried doing SELECT * FROM lessons_slots LEFT JOIN class_roll ON lessons_slots.ID = class_roll.classid WHERE lessons_slots.name != 'advanced' But that doesn't work. Any ideas?

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• Problem accessing base member in derived constructor

  - by LeopardSkinPillBoxHat

  Given the following classes: class Foo { struct BarBC { protected: BarBC(uint32_t aKey) : mKey(aKey) mOtherKey(0) public: const uint32_t mKey; const uint32_t mOtherKey; }; struct Bar : public BarBC { Bar(uint32_t aKey, uint32_t aOtherKey) : BarBC(aKey), mOtherKey(aOtherKey) // Compile error here }; }; I am getting a compilation error at the point indicated: error: class `Foo::Bar' does not have any field named `mOtherKey'. Can anyone explain this? I suspect it's a syntactical problem due to my Bar class being defined within the Foo class, but can't seem to find a way around it. This is simple public inheritance, so mOtherKey should be accessible from the Bar constructor. Right? Or is it something to do with the fact that mOtherKey is const and I have already initialised it to 0 in the BarBC constructor?

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• passing data from an activity to an listactivity or listview

  - by wicked14

  need help on passing data from an activity to an listactivity or listview for an android app. im having problems on passing data to a listview. what the app do is from addact class the user can input things to do and in the viewact class this will display the activies add by the user in listview public class addact extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.newact); Button btn1 = (Button)findViewById(R.id.btnsave); final EditText et1 = (EditText)findViewById(R.id.etactivity); btn1.setOnClickListener(new OnClickListener() { @Override public void onClick(View arg0) { Intent it = new Intent(addact.this, viewact.class); it.putExtra("thekey", et1.getText().toString()); startActivity(it); } }); } } public class viewact extends ListActivity { String addToDo =getIntent().getExtras().getString("thekey"); String[] toDoAct = new String[] {addToDo }; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.viewact); setListAdapter(new ArrayAdapter<String>(this, R.layout.viewact,toDoAct)); ListView listView = getListView(); listView.setTextFilterEnabled(true); listView.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> parent, View view, int position, long id) { for (int i=0; i < 2; i++) { Toast.makeText(getApplicationContext(), ((TextView) view).getText(), Toast.LENGTH_LONG).show(); } } }); } }

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• Questions about use lib for perl

  - by Tyug

  I use use lib "./DIR" to grab a library from a folder elsewhere. However, it doesn't seem to work on my server, but it works fine on my local desktop. Any particular reasons? And one more question, does use lib get propagated within several modules? Two situations: Say I make a base class that requires a few libraries, but I know that it needs to be extended and the extended class will need to use another library. Can I put the use lib command in the base class? or will I need to put it in every extending class? Finally, can I just have a use package where package contains a bunch of use lib, will it propagate the use lib statements over to my current module? <-- I don't think so, but asking anyways Thanks in advance! Tyug

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• "Inherited" types in C++

  - by Ken Moynihan

  The following code does not compile. I get an error message: error C2039: 'Asub' : is not a member of 'C' Can someone help me to understand this? Tried VS2008 & 2010 compiler. template <class T> class B { typedef int Asub; public: void DoSomething(typename T::Asub it) { } }; class C : public B<C> { public: typedef int Asub; }; class A { public: typedef int Asub; }; int _tmain(int argc, _TCHAR* argv[]) { C theThing; theThing.DoSomething(C::Asub()); return 0; }

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• Extending existing data structure in Scala.

  - by Lukasz Lew

  I have a normal tree defined in Scala. sealed abstract class Tree case class Node (...) extends Tree case class Leaf (...) extends Tree Now I want to add a member variable to all nodes and leaves in the tree. Is it possible with extend keyword or do I have to modify the tree classes by adding [T]?

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• Wierdness debugging Visual Studio C++ 2008

  - by Jeff Dege

  I have a legacy C++ app, that in its most incarnation we've been building with makefiles and VS2003's command-line tool. I'm trying to get it to build using VS2008 and MsBuild. The build is working OK, but I'm getting errors where I'd never seen errors, before, and stepping through in VS2008's debugger only confuses me. The app links a number of static libraries, which fall into two categories: those that are part of the same application suite, and those that are shared between a number of application suites. Originally, I had a .csproj file for each static library, and two .sln files, one for the application suite (including the suite-specific libraries) and one for the non-suite-specific shared libraries. The shared libraries were included in the link, their projects were not included in the application suite .sln. The application instantiates an object from a class that is defined in one of the shared libraries. The class has a member object of a class that wraps a linked list. The constructor of the linked list class sets its "head" pointer to null. When I run the app, and try to add an element to the linked list, I get an error - the head pointer contains the value 0xCCCCCCCC. So I step through with the debugger. And see weirdness. When the current line in the debugger is in a source file belonging to the static library, the head pointer contains 0x00000000. When I step into the constructor, I can see the pointer being set to that value, and when I'm stepped into any other method of the class, I can see that the head pointer still contains 0x00000000. But when I step out into methods that are defined in the application suite .sln, it contains 0xCCCCCCCC. It's not like it's being overwritten. It changes back and forth depending upon which source file I am currently debugging. So I included the shared library's project in the application suite .sln, and now I see the head pointer containing 0xCCCCCCCC all the time. It looks like the constructor of the linked list class is not being called. So now, I'm entirely confused. Anyone have any ideas?

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• How to use interfaces in exception handling

  - by vikp

  Hi, I'm working on the exception handling layer for my application. I have read few articles on interfaces and generics. I have used inheritance before quite a lot and I'm comfortable with in that area. I have a very brief design that I'm going to implement: public interface IMyExceptionLogger { public void LogException(); // Helper methods for writing into files,db, xml } I'm slightly confused what I should be doing next. public class FooClass: IMyExceptionLogger { // Fields // Constructors } Should I implement LogException() method within FooClass? If yes, than I'm struggling to see how I'm better of using an interface instead of the concrete class... I have a variety of classes that will make a use of that interface, but I don't want to write an implementation of that interface within each class. In the same time If I implement an interface in one class, and then use that class in different layers of the application I will be still using concrete classes instead of interfaces, which is a bad OO design... I hope this makes sense. Any feedback and suggestions are welcome. Please notice that I'm not interested in using net4log or its competitors because I'm doing this to learn. Thank you Edit: Wrote some more code. So I will implement variety of loggers with this interface, i.e. DBExceptionLogger, CSVExceptionLogger, XMLExceptionLogger etc. Than I will still end up with concrete classes that I will have to use in different layers of my application.

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• Why is C# statically typed?

  - by terrani

  I am a PHP web programmer who is trying to learn C#. I would like to know why C# requires me to specify the data type when creating a variable. Class classInstance = new Class(); Why do we need to know the data type before a class instance?

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• How to configure Spring-DM OSGi service for new instance per call?

  - by Bhav

  I'm starting to delve into using Spring DM and OSGi services in an RCP application. I've created a service which is used by another bundle in the RCP application. It does a lookup of the service via calls to getBundleContext().getServiceReference() using the explicit bundle names and service class names. I'm not using DI anywhere yet. The issue I'm running into is that the service that is returned in the requesting bundle is a singleton. At times I notice a threading issue since it is a "stateful" service. How do I configure the application to get back a new service instance with each call? Here is my spring xml file contents which registers the service: <bean id="myServBean" class="com.xyz.ClassImpl"/> <osgi:service ref="myServBean" class="com.xyz.Class"/>

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• C++ initializing constants and inheritance

  - by pingvinus

  I want to initialize constant in child-class, instead of base class. And use it to get rid of dynamic memory allocation (I know array sizes already, and there will be a few child-classes with different constants). So I try: class A { public: const int x; A() : x(0) {} A(int x) : x(x) {} void f() { double y[this->x]; } }; class B : A { B() : A(2) {} }; Pretty simple, but compiler says: error C2057: expected constant expression How can I say to compiler, that it is really a constant?

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• What's the "proper" way to retrieve a reference to a ribbon object?

  - by Nick

  For a VSTO workbook project, is there a best practice for retrieving a reference to the Ribbon object from the ThisWorkbook class? Here's what I'm doing: In my Ribbon class, I created a public method called InvalidateControl(string controlID). I need to call that method from the ThisWorkbook class based on when a certain workbook level event fires. But the only way I can see to "get" a reference to that Ribbon object is to do this... // This is all in the ThisWorkbook class Ribbon ribbon; protected override IRibbonExtensibility CreateRibbonExtensibilityObject() { this.ribbon = new Ribbon(); return this.ribbon; } ...which seems a little smelly. I mean, I have to override CreateRibbonExtensibilityObject() regardless; all I'm doing beyond that is maintaining a local reference to the ribbon so I can call methods against it. But it doesn't feel right. Is there another, better way to get that reference in the ThisWorkbook class? Or is this pretty acceptable? Thanks!

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• Inheriting database connection in PHP OOP

  - by vrode

  My abstract class Database is made for database interaction and any child of this class (UserDatabase, ActionDatabase, EventDatabase) inherits its database connection which is defined as static. `abstract class Database { static $connection = mysql_connect( ); } class UserDatabase extends Database { ... public function __construct( ) { $connection ? "connected" : "not connected"; $this-table = "users"; mysql_query( "FROM " . $this-table . " SELECT *" ); } } ` Does that mean, that my database connection is only set up and stored in memory once and passed on to subclasses as reference without being replicated for each instance? Is this how you would implement you OOP-correct database interface?

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• What is an efficient way to find a non-colliding rectangle nearest to a location

  - by hyn

  For a 2D game I am working on, I am using y axis sorting in a simple rectangle-based collision detection. This is working fine, and now I want to find the nearest empty rectangle at a given location with a given size, efficiently. How can I do this? Is there an algorithm? I could think of a simple brute force grid test (with each grid the size of the empty space we're looking for) but obviously this is slow and not even a complete test.

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• Does this code describe an Existential Type in C#?

  - by noblethrasher

  Currently watching Bart De Smet's explanation of IQueryable and he mentioned Existential Types (which I've been curious about for some time). After reading the answers to this question I'm just wondering if this is a way to construct it in C#: public abstract class ExistentialType { private ExistentialType() { } public abstract int Foo(); public ExistentialType Create() { return new ConcreateType1(); } private class ConcreateType1 : ExistentialType { public override int Foo() { throw new NotImplementedException(); } } private class ConcreateType2 : ExistentialType { public override int Foo() { throw new NotImplementedException(); } } private class ConcreateType3 : ExistentialType { public override int Foo() { throw new NotImplementedException(); } } }

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• Is a many-to-many relationship with extra fields the right tool for my job?

  - by whichhand

  Previously had a go at asking a more specific version of this question, but had trouble articulating what my question was. On reflection that made me doubt if my chosen solution was correct for the problem, so this time I will explain the problem and ask if a) I am on the right track and b) if there is a way around my current brick wall. I am currently building a web interface to enable an existing database to be interrogated by (a small number of) users. Sticking with the analogy from the docs, I have models that look something like this: class Musician(models.Model): first_name = models.CharField(max_length=50) last_name = models.CharField(max_length=50) dob = models.DateField() class Album(models.Model): artist = models.ForeignKey(Musician) name = models.CharField(max_length=100) class Instrument(models.Model): artist = models.ForeignKey(Musician) name = models.CharField(max_length=100) Where I have one central table (Musician) and several tables of associated data that are related by either ForeignKey or OneToOneFields. Users interact with the database by creating filtering criteria to select a subset of Musicians based on data the data on the main or related tables. Likewise, the users can then select what piece of data is used to rank results that are presented to them. The results are then viewed initially as a 2 dimensional table with a single row per Musician with selected data fields (or aggregates) in each column. To give you some idea of scale, the database has ~5,000 Musicians with around 20 fields of related data. Up to here is fine and I have a working implementation. However, it is important that I have the ability for a given user to upload there own annotation data sets (more than one) and then filter and order on these in the same way they can with the existing data. The way I had tried to do this was to add the models: class UserDataSets(models.Model): user = models.ForeignKey(User) name = models.CharField(max_length=100) description = models.CharField(max_length=64) results = models.ManyToManyField(Musician, through='UserData') class UserData(models.Model): artist = models.ForeignKey(Musician) dataset = models.ForeignKey(UserDataSets) score = models.IntegerField() class Meta: unique_together = (("artist", "dataset"),) I have a simple upload mechanism enabling users to upload a data set file that consists of 1 to 1 relationship between a Musician and their "score". Within a given user dataset each artist will be unique, but different datasets are independent from each other and will often contain entries for the same musician. This worked fine for displaying the data, starting from a given artist I can do something like this: artist = Musician.objects.get(pk=1) dataset = UserDataSets.objects.get(pk=5) print artist.userdata_set.get(dataset=dataset.pk) However, this approach fell over when I came to implement the filtering and ordering of query set of musicians based on the data contained in a single user data set. For example, I could easily order the query set based on all of the data in the UserData table like this: artists = Musician.objects.all().order_by(userdata__score) But that does not help me order by the results of a given single user dataset. Likewise I need to be able to filter the query set based on the "scores" from different user data sets (eg find all musicians with a score 5 in dataset1 and < 2 in dataset2). Is there a way of doing this, or am I going about the whole thing wrong?

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• Get Confirm value in vb.net

  - by user1805641

  I have a hidden asp Button in a Repeater. In the VB.NET code behind I use the Rerpeater_ItemCommand to get the click event within the Repeater. There's a check if user is already recording a project. If yes and he wants to start a new one, a confirm box should appear asking "Are you sure?" How can I access the click value from confirm? <asp:Repeater ID="Repeater1" runat="server" OnItemCommand="Repeater1_ItemCommand"> <ItemTemplate> <div class="tile user_view user_<%# Eval("employeeName") %>"> <div class="tilesheight"></div> <div class="element"> <asp:Button ID="Button1" CssClass="hiddenbutton" runat="server" /> Index: <asp:Label ID="Label1" runat="server" Text='<%# Eval("index") %>' /><br /> <hr class="hr" /> customer: <asp:Label ID="CustomerLabel" runat="server" Text='<%# Eval("customer") %>' /><br /> <hr class ="hr" /> order: <asp:Label ID="OrderNoLabel" runat="server" Text='<%# Eval("orderNo") %>' /><br /> <asp:Label ID="DescriptionLabel" runat="server" Text='<%# Eval("description") %>' /><br /> <hr class="hr" /> </div> </div> </ItemTemplate> </asp:Repeater> code behind: If empRecs.Contains(projects.Item(index.Text).employeeID) Then 'Catch index of recording order i = empRecs.IndexOf(projects.Item(index.Text).employeeID) Page.ClientScript.RegisterStartupScript(Me.GetType, "confirm", "confirm('Order " & empRecs(i + 2) & " already recording. Would you like to start a new one?')",True) 'If users clicks ok insertData() End If Other solutions are using the Click Event and a hidden field. But the problem is, I don't want the confirmbox to appear every time the button is clicked. Only when empRecs conatins an employee. Thanks for helping

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• How do I get 2-way data binding to work for nested asp.net Repeater controls

  - by jimblanchard

  I have the following (trimmed) markup: <asp:Repeater ID="CostCategoryRepeater" runat="server"> <ItemTemplate> <div class="costCategory"> <asp:Repeater ID="CostRepeater" runat="server" DataSource='<%# Eval("Costs")%>'> <ItemTemplate> <tr class="oddCostRows"> <td class="costItemTextRight"><span><%# Eval("Variance", "{0:c0}")%></span></td> <td class="costItemTextRight"><input id="SupplementAmount" class="costEntryRight" type="text" value='<%# Bind("SupplementAmount")%>' runat="server" /></td> </tr> </ItemTemplate> </asp:Repeater> </div> </ItemTemplate> </asp:Repeater> The outer repeater's DataSource is set in the code-beside. I've snipped them, but there are Eval statements that wire up to the properties in the outer Repeater. Anyway, one of the fields in the inner Repeater needs to be a Bind instead of an Eval, as I want to get the values that the user types in. The SupplementAmount input element correctly receives it's value when the page loads, but on the other side, when I inspect the contents of the Costs List when the form posts back, the changes the user made aren't present. Thanks.

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• Why are we getting a WCF "Framing error" on some machines but not others

  - by Ian Ringrose

  We have just found we are getting “framing errors” (as reported by the WCF logs) when running our system on some customer test machine. It all works ok on our development machines. We have an abstract base class, with KnownType attributes for all its sub classes. One of it’s subclass is missing it’s DataContract attribute. However it all worked on our test machine! On the customers test machine, we got “framing error” showing up the WCF logs, this is not the error message I have seen in the past when missing a DataContract attribute, or a KnownType attribute. I wish to get to the bottom of this, as we can no longer have confidence in our ability to test the system before giving it to the customer until we can make our machines behave the some as the customer’s machines. Code that try to show what I am talking about, (not the real code) [DataContract()] [KnownType(typeof(SubClass1))] [KnownType(typeof(SubClass2))] // other subclasses with data members public abstract class Base { [DataMember] public int LotsMoreItemsThenThisInRealLife; } /// <summary> /// This works on some machines (not not others) when passed to Contract::DoIt, /// note the missing [DataContract()] /// </summary> public class SubClass1 : Base { // has no data members } /// <summary> /// This works in all cases when passed to Contract::DoIt /// </summary> [DataContract()] public class SubClass2 : Base { // has no data members } public interface IContract { void DoIt(Base[] items); } public static class MyProgram { public static IContract ConntectToServerOverWCF() { // lots of code ... return null; } public static void Startup() { IContract server = ConntectToServerOverWCF(); // this works all of the time server.DoIt(new Base[]{new SubClass2(){LotsMoreItemsThenThisInRealLife=2}}); // this works "in develperment" e.g. on our machines, but not on the customer's test machines! server.DoIt(new Base[] { new SubClass1() { LotsMoreItemsThenThisInRealLife = 2 } }); } }

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