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• Can Bonjour browse a service with a particular name?

  - by Roman

  Bonjour provides "DNSSD.browse(serviceType,callBackObject)" method which browses for services of a particular type. If a service of the given type is found, Bonjour call "callBackObject.serviceFound". If the service is lost, Bonjour calls "callBackObject.serviceLost". I alway considered "DNSSD.browse" as a method for monitoring a particular service. Bonjour monitors a particular service and calls necessary method if the service is found (available) or lost (not available). But than I realized that "DNSSD.browse" receives (as argument) a type of service (for example "http.tcp") and there can be several services of this type. So, its probably calls "serviceFound" and "serviceLost" if any service of the specified type is found or lost, respectively. But in my application I would like to browse just for one particular service. What is the best way to do it? I have two potential solutions: When I register a service, I give it a unique type. For example: "server1.http.tcp". I register services with unique names (not types) and ask Bonjour to browse for services with particular names. But I am not sure that Bonjour provide such possibility. Can it browse for services with specific names?

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• switching C compiler causes: Error Initializer cannot be specified for a flexible array member

  - by user1054210

  I am trying to convert our code from one IDE to be used in a different one. The current one uses gcc which allows for this structure to be initialized from a variable array. The new tool does not use gcc gives me an error "Initializer cannot be specified for a flexible array member". So can someone help me understand how to set this up? Should I set up a blank array of variable size and then somewhere assign the #define array as seen below? Here would be an example of the code…(this is current implementation current IDE) In one header file that is Build switchable so we can build this on different hardware platforms we have the following #define #define GPIOS \ /* BANK, PIN, SPD, MODE,… */ GPIOINIT( A, 0, 2, AIN, …) \ GPIOINIT( A, 1, 2, AIN, …) \ GPIOINTINIT(A, 2, 2, AIN, …) \ . . . Then in a different header file that is used in all builds we have PLATFORM_CONFIG_T g_platformConfig = { .name = {PLATFORM_NAME}, (bunch of other stuff), .allGpios = { GPIOS /* here I get the error */ }, }; So I am thinking I can make the error line a variable array and assign to it later in some other way? The problem is the actual array "GPIO" is of different types and pin orders on different designs are different.

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• Best practice - logging events (general) and changes (database)

  - by b0x0rz

  need help with logging all activities on a site as well as database changes. requirements: * should be in database * should be easily searchable by initiator (user name / session id), event (activity type) and event parameters i can think of a database design but either it involves a lot of tables (one per event) so i can log each of the parameters of an event in a separate field OR it involves one table with generic fields (7 int numeric and 7 text types) and log everything in one table with event type field determining what parameter got written where (and hoping that i don't need more than 7 fields of a certain type, or 8 or 9 or whatever number i choose)... example of entries (the usual things): [username] login failed @datetime [username] login successful @datetime [username] changed password @datetime, estimated security of password [low/ok/high/perfect] @datetime [username] clicked result [result number] [result id] after searching for [search string] and got [number of results] @datetime [username] clicked result [result number] [result id] after searching for [search string] and got [number of results] @datetime [username] changed profile name from [old name] to [new name] @datetime [username] verified name with [credit card type] credit card @datetime datbase table [table name] purged of old entries @datetime via automated process etc... so anyone dealt with this before? any best practices / links you can share? i've seen it done with the generic solution mentioned above, but somehow that goes against what i learned from database design, but as you can see the sheer number of events that need to be trackable (each user will be able to see this info) is giving me headaches, BUT i do LOVE the one event per table solution more than the generic one. any thoughts? edit: also, is there maybe an authoritative list of such (likely) events somewhere? thnx stack overflow says: the question you're asking appears subjective and is likely to be closed. my answer: probably is subjective, but it is directly related to my issue i have with designing a database / writing my code, so i'd welcome any help. also i tried narrowing down the ideas to 2 so hopefully one of these will prevail, unless there already is an established solution for these kinds of things.

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• Reordering methods in ComImport interfaces throws COMException (0x80041001)

  - by Ohad Schneider

  Consider the following code for COM interop with internet shortcuts: [ComImport] [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)] [Guid("CABB0DA0-DA57-11CF-9974-0020AFD79762")] public interface IUniformResourceLocatorW { void SetUrl([MarshalAs(UnmanagedType.LPWStr)] string pcszUrl, int dwInFlags); void GetUrl([MarshalAs(UnmanagedType.LPWStr)] out StringBuilder ppszUrl); void InvokeCommand(IntPtr purlici); } [ComImport] [Guid("FBF23B40-E3F0-101B-8488-00AA003E56F8")] public class InternetShortcut { } The following works as expected: var ishort = new InternetShortcut(); ((IPersistFile)ishort).Load("MyLink.url", 0); ((IUniformResourceLocatorW)ishort).GetUrl(out url); However: If I comment out IUniformResourceLocatorW.SetUrl (which I am not using), IUniformResourceLocatorW.GetUrl throws a COMException (HResult 0x80041001). If I switch between IUniformResourceLocatorW.SetUrl and IUniformResourceLocatorW.GetUrl (that is place the former below the latter) the same exception is thrown If I comment out IUniformResourceLocatorW.InvokeCommand the code runs fine. It's as if the order has to be preserved "up to" the invoked method. Is this behavior by design? documented somewhere? I'm asking because some COM interfaces are composed of many methods with possibly many supporting types and I'd rather avoid defining what I don't need if possible.

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• Java inheritance and super() isn't working as expected

  - by dwwilson66

  For a homework assignment, I'm working with the following. It's an assigned class structure, I know it's not the best design by a long shot. Class | Extends | Variables -------------------------------------------------------- Person | None | firstName, lastName, streetAddress, zipCode, phone CollegeEmployee | Person | ssn, salary,deptName Faculty | CollegeEmployee | tenure(boolean) Student | person | GPA,major So in the Faculty class... public class Faculty extends CollegeEmployee { protected String booleanFlag; protected boolean tenured; public Faculty(String firstName, String lastName, String streetAddress, String zipCode, String phoneNumber,String ssn, String department,double salary) { super(firstName,lastName,streetAddress,zipCode,phoneNumber, ssn,department,salary); String booleanFlag = JOptionPane.showInputDialog (null, "Tenured (Y/N)?"); if(booleanFlag.equals("Y")) tenured = true; else tenured = false; } } It was my understanding that super() in Faculty would allow access to the variables in CollegeEmployee as well as Person. With the code above, it compiles fine when I ONLY include the Person variables. As soon as I try to use ssn, department, or salary I get the following compile errors. Faculty.java:15: error: constructor CollegeEmployee in class CollegeEmployee can not be applied to the given types: super(firstName,lastName,streetAddress,zipCode,phoneNumber,ssn,department,salary); ^ Required: String,String,String,String,String Found: String,String,String,String,String,String,String,String reason: actual and formal argument lists differ in length I'm completely confused by this error...which is the actual and formal? Person has five arguments, CollegeEmployee has 3, so my guess is that something's funky with how the parameters are being passed...but I'm not quite sure where to begin fixing it. What am I missing?

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• Return type from DAL class (Sql ce, Linq to Sql)

  - by bretddog

  Hi, Using VS2008 and Sql CE 3.5, and preferably Linq to Sql. I'm learning database, and unsure about DAL methods return types and how/where to map the data over to my business objects: I don't want direct UI binding. A business object class UserData, and a class UserDataList (Inherits List(Of UserData)), is represented in the database by the table "Users". I use SQL Compact and run SqlMetal which creates dbml/designer.vb file. This gives me a class with a TableAttribute: <Table()> _ Partial Public Class Users I'm unsure how to use this class. Should my business object know about this class, such that the DAL can return the type Users, or List(Of Users) ? So for example the "UserDataService Class" is a part of the DAL, and would have for example the functions GetAll and GetById. Will this be correct : ? Public Class UserDataService Public Function GetAll() As List(Of Users) Dim ctx As New MyDB(connection) Dim q As List(Of Users) = From n In ctx.Users Select n Return q End Function Public Function GetById(ByVal id As Integer) As Users Dim ctx As New MyDB(connection) Dim q As Users = (From n In ctx.Users Where n.UserID = id Select n).Single Return q End Function And then, would I perhaps have a method, say in the UserDataList class, like: Public Class UserDataList Inherits List(Of UserData) Public Sub LoadFromDatabase() Me.clear() Dim database as New UserDataService dim users as List(Of Users) users = database.GetAll() For each u in users dim newUser as new UserData newUser.Id = u.Id newUser.Name = u.Name Me.Add(newUser) Next End Sub End Class Is this a sensible approach? Would appreciate any suggestions/alternatives, as this is my first attempt on a database DAL. cheers!

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• Dynamically compose ASP MVC view based on context

  - by robertFall

  I have several views that are composed of several partial views based on context. For example, we have a Project view that shows all the details of a project, which includes the scalar values, name etc, and also all the assigned employees, tasks and/or clients. The problem I have is that certain types of project have all of the above sections while others have only two or even on section, ie. details only. What is the best way to compose the Projects master view? I don't want to have logic to check the project in the view. Is there a way to compose a view in code by programatically rendering the relevant partials and ignoring the rest? Otherwise are there any other ideas how to do this in a maintainable way? I could of course just render the partials using if statements to check if they apply, but that way the view contains VERY important logic. In another situation we want to use this method to display content based on the type of subscription a user has. Thanks!

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• Setting up Inversion of Control (IoC) in ASP.NET MVC with Castle Windsor

  - by Lirik

  I'm going over Sanderson's Pro ASP.NET MVC Framework and in Chapter 4 he discusses Creating a Custom Controller Factory and it seems that the original method, AddComponentLifeStyle or AddComponentWithLifeStyle, used to register controllers is deprecated now: public class WindsorControllerFactory : DefaultControllerFactory { IWindsorContainer container; public WindsorControllerFactory() { container = new WindsorContainer(new XmlInterpreter(new ConfigResource("castle"))); // register all the controller types as transient var controllerTypes = from t in Assembly.GetExecutingAssembly().GetTypes() where typeof(IController).IsAssignableFrom(t) select t; //[Obsolete("Use Register(Component.For<I>().ImplementedBy<T>().Named(key).Lifestyle.Is(lifestyle)) instead.")] //IWindsorContainer AddComponentLifeStyle<I, T>(string key, LifestyleType lifestyle) where T : class; foreach (Type t in controllerTypes) { container.Register(Component.For<IController>().ImplementedBy<???>().Named(t.FullName).LifeStyle.Is(LifestyleType.Transient)); } } // Constructs the controller instance needed to service each request protected override IController GetControllerInstance(Type controllerType) { return (IController)container.Resolve(controllerType); } } The new suggestion is to use Register(Component.For<I>().ImplementedBy<T>().Named(key).Lifestyle.Is(lifestyle)), but I can't figure out how to present the implementing controller type in the ImplementedBy<???>() method. I tried ImplementedBy<t>() and ImplementedBy<typeof(t)>(), but I can't find the appropriate way to pass int he implementing type. Any ideas?

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• Performance impact when using XML columns in a table with MS SQL 2008

  - by Sam Dahan

  I am using a simple table with 6 columns, 3 of which are of XML type, not schema-constrained. When the table reaches a size around 120,000 or 150,000 rows, I see a dramatic performance cost in doing any query in the table. For comparison, I have another table, which grows in size at about the same rate, but only contain scalar types (int, datetime, a few float columns). That table performs perfectly fine even after 200,000 rows. And by the way, I am not using XQuery on the xml columns, i am only using regular SQL query statements. Some specifics: both tables contain a DateTime field called SampleTime. a statement like (it's in a stored procedure but I show you the actual statement) SELECT MAX(sampleTime) SampleTime FROM dbo.MyRecords WHERE PlacementID=@somenumber takes 0 seconds on the table without xml columns, and anything from 13 to 20 seconds on the table with XML columns. That depends on which drive I set my database on. At the moment it sits on a different spindle (not C:) and it takes 13 seconds. Has anyone seen this behavior before, or have any hint at what I am doing wrong? I tried this with SQL 2008 EXPRESS and the full-blown SQL Server 2008, that made no difference. Oh, one last detail: I am doing this from a C# application, .NET 3.5, using SqlConnection, SqlReader, etc.. I'd appreciate some insight into that, thanks! Sam

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• Interpreting java.lang.NoSuchMethodError message

  - by Doog

  I get the following runtime error message (along with the first line of the stack trace, which points to line 94). I'm trying to figure out why it says no such method exists. java.lang.NoSuchMethodError: com.sun.tools.doclets.formats.html.SubWriterHolderWriter.printDocLinkForMenu( ILcom/sun/javadoc/ClassDoc;Lcom/sun/javadoc/MemberDoc; Ljava/lang/String;Z)Ljava/lang/String; at com.sun.tools.doclets.formats.html.AbstractExecutableMemberWriter.writeSummaryLink( AbstractExecutableMemberWriter.java:94) Line 94 of writeSummaryLink is shown below. QUESTIONS What does "ILcom" or "Z" mean? Why there are four types in parentheses (ILcom/sun/javadoc/ClassDoc;Lcom/sun/javadoc/MemberDoc;Ljava/lang/String;Z) and one after the parentheses Ljava/lang/String; when the method printDocLinkForMenu clearly has five parameters? CODE DETAIL The writeSummaryLink method is: protected void writeSummaryLink(int context, ClassDoc cd, ProgramElementDoc member) { ExecutableMemberDoc emd = (ExecutableMemberDoc)member; String name = emd.name(); writer.strong(); writer.printDocLinkForMenu(context, cd, (MemberDoc) emd, name, false); // 94 writer.strongEnd(); writer.displayLength = name.length(); writeParameters(emd, false); } Here's the method line 94 is calling: public void printDocLinkForMenu(int context, ClassDoc classDoc, MemberDoc doc, String label, boolean strong) { String docLink = getDocLink(context, classDoc, doc, label, strong); print(deleteParameterAnchors(docLink)); }

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• Static files in (Java) App Engine not accessible.

  - by fiXedd

  The example documentation says that you simply need to place your files in war/ (or a subdirectory) and they should be accessible from the host (as long as they aren't JSPs or in WEB-INF). For example, if you place foo.css in war/ then you should be able to access it at http://localhost:8080/foo.css. However, this isn't working for me at all. NONE of my static files are accessible. The docs on appengine-web.xml say that you can also specifically denote certain types as static. I've tried this as well and it makes no difference. Am I missing something obvious? UPDATE: Turns out one of the mappings in my web.xml was a little too aggressive. The following was the culprit: <servlet> <servlet-name>Main</servlet-name> <servlet-class>MainServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>Main</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> It seems that it was grabbing everything that wasn't grabbed be one of the other rules, which I don't understand because there was no * on the end of the url-pattern. It also seems to be directly contradictory to the documentation that says: Note: Static files, files that are served verbatim to users such as images, CSS or JavaScript, are handled separately from paths mentioned in the deployment descriptor. A request for a URL path that matches a path to a file in the WAR that's considered a static file will serve the file, regardless of servlet and filter mappings in the deployment descriptor. You can exclude files from those treated as static files using the appengine-web.xml file. So, how can I have a rule that matches the base of my domain (eg. http://www.example.com/) and still allows the static files to filter through?

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• How to define trees with more than one type in ML programing language

  - by user550413

  Well, I am asked to do the next thing: To define a binary tree which can contain 2 different types: ('a,'b) abtree and these are the requirements: Any inner vertex (not a leaf) must be of the type 'a or 'b and the leafs have no value. For every path in the tree all 'a values must appear before the 'b value: examples of paths: 'a->'a->'a-'b (legal) 'a->'b->'b (legal) 'a->'a->'a (legal) 'b->'b->'b (legal) 'a->'b->'a (ILLEGAL) and also I need to define another tree which is like the one described above but now I have got also 'c and in the second requirement it says that for every path I 'a values appear before the 'b values and all the 'b values appear before the 'c values. First, I am not sure how to define binary trees to have more than 1 type in them. I mean the simplest binary tree is: datatype 'a tree = leaf | br of 'a * 'a tree * 'a tree; And also how I can define a tree to have these requirements. Any help will be appreciated. Thanks.

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• What should I do if i have a factory method which requires different parameters for different implem

  - by Sam Holder

  I have an interface, IMessage and a class which have several methods for creating different types of message like so: class MessageService { IMessage TypeAMessage(param 1, param 2) IMessage TypeBMessage(param 1, param 2, param 3, param 4) IMessage TypeCMessage(param 1, param 2, param 3) IMessage TypeDMessage(param 1) } I don't want this class to do all the work for creating these messages so it simply delegates to a MessageCreatorFactory which produces an IMessageCreator depending on the type given (an enumeration based on the type of the message TypeA, TypeB, TypeC etc) interface IMessageCreator { IMessage Create(MessageParams params); } So I have 4 implementations of IMessageCreator: TypeAMessageCreator, TypeBMessageCreator, TypeCMessageCreator, TypeDMessageCreator I ok with this except for the fact that because each type requires different parameters I have had to create a MessageParams object which contains 4 properties for the 4 different params, but only some of them are used in each IMessageCreator. Is there an alternative to this? One other thought I had was to have a param array as the parameter in the Create emthod, but this seems even worse as you don't have any idea what the params are. Or to create several overloads of Create in the interface and have some of them throw an exception if they are not suitable for that particular implementation (ie you called a method which needs more params, so you should have called one of the other overloads.) Does this seem ok? Is there a better solution?

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• Getting error when compiling debug mode: C++/CLI - error LNK2022

  - by Yochai Timmer

  I've got a CLI code wrapping a C++ DLL. When i try to compile it in debug mode, i get the following error: Error 22 error LNK2022: metadata operation failed (8013118D) : Inconsistent layout information induplicated types .... MSVCMRTD.lib (locale0_implib.obj) The weird thing is that on Release mode it compiles OK and works OK. The only difference i can see that causes the problem is when i change: Configuration Properties - C/C++ - Code Generation - Runtime Library When it's set to: Multi-threaded Debug DLL (/MDd) it throws the error. When it's set to: Multi-threaded DLL (/MD) it compiles fine. The same settings work for all the other DLLs in the project (CLI and C++) and they inherit the same properties. I'm using VS2010. So, how can i solve this ? And can I get some explanation to WHY this is happening ? Update: I've basically tried changing every option in the project's properties with no luck. I've read somewhere that this might be caused from duplicate declarations of a type of the same name. But in the CLI file i'm calling std::string etc. explicitly from std. Any other ideas ?

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• Expand chaining hashtable. Errors on code.

  - by FILIaS

  Expanding a hashtable with linked lists there are some errors and warnings. I wanna make sure that the following code is right (expand method) and find out what happens that raise these warnings/errors typedef struct { int length; struct List *head; struct List *tail; } HashTable; //resolving collisions using linked lists - chaining typedef struct { char *number; char *name; int time; struct List *next; }List; //on the insert method i wanna check hashtable's size, //if it seems appropriate there is the following code: //Note: hashtable variable is: Hashtable * ...... hashtable = expand(hashtable,number,name,time); /**WARNING**:assignment makes pointer from integer without a cast*/ HashTable* expand( HashTable* h ,char number[10],char* name,int time) /**error**: conflicting types for ‘expand’ previous implicit declaration of ‘expand’ was here*/ { HashTable* new; int n; clientsList *node,*next; PrimesIndex++; int new_size= primes[PrimesIndex]; /* double the size,odd length */ if (!(new=malloc((sizeof( List*))*new_size))) return NULL; for(n=0; n< h->length; ++n) { for(node=h[n].head; node; node=next) { add (&new, node->number, node->name,node->time); next=node->next;//// free(node); } } free(h); return new; }

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• Accept templated parameter of stl_container_type<string>::iterator

  - by Rodion Ingles

  I have a function where I have a container which holds strings (eg vector<string>, set<string>, list<string>) and, given a start iterator and an end iterator, go through the iterator range processing the strings. Currently the function is declared like this: template< typename ContainerIter> void ProcessStrings(ContainerIter begin, ContainerIter end); Now this will accept any type which conforms to the implicit interface of implementing operator*, prefix operator++ and whatever other calls are in the function body. What I really want to do is have a definition like the one below which explicitly restricts the amount of input (pseudocode warning): template< typename Container<string>::iterator> void ProcessStrings(Container<string>::iterator begin, Container<string>::iterator end); so that I can use it as such: vector<string> str_vec; list<string> str_list; set<SomeOtherClass> so_set; ProcessStrings(str_vec.begin(), str_vec.end()); // OK ProcessStrings(str_list.begin(), str_list.end()); //OK ProcessStrings(so_set.begin(), so_set.end()); // Error Essentially, what I am trying to do is restrict the function specification to make it obvious to a user of the function what it accepts and if the code fails to compile they get a message that they are using the wrong parameter types rather than something in the function body that XXX function could not be found for XXX class.

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• problem in showing and hiding dialog boxes in MFC

  - by Rakesh

  Hello all, I am trying to create a wizard like structure using dialog boxes...So I replaced the code in CDialog1App as below CDialog1Dlg* dlg = new CDialog1Dlg; m_pMainWnd = dlg; dlg->Create(IDD_DIALOG1); dlg->ShowWindow(SW_SHOW); the above worked fine...its displying the dialog box.but I have added another dialog box... So in the first dialog box if the user clicks Next it has to hide the first dialog box and display the second dialog.. //CDialog1 class void CDialog1Dlg::OnBnClickedNext() { // TODO: Add your control notification handler code here CDialog2* dialog2 = new CDialog2(); dialog2->Create(IDD_DIALOG2); dialog2->ShowWindow(SW_SHOW); this->ShowWindow(SW_HIDE); } in the above code am creating an object for the Dialog2 class and trying to show that.... Now the problem is,when I click next its hiding both the windows..What can I do..I tried several types but its still its not workin..Please dont suggest me to do with PropertySheet..It will work with that, i know ...but I want this using Dialog Box for some reason

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• Visual Studio breaks, and steps, but sometimes steps out

  - by James Wilkins

  Something very odd is going on. It's been going on for some time, but I've just ignored it up to now. I have both a Silverlight and WCF service in my solution, which shares .CS file between them (one project has a link to the file, which exists in the other project). While debugging the Silverlight app, pressing the F10 key steps through code as normal, and when I get to a method call which exists in the shared file (between the projects), and Press F11, it simply skips the method instead of stepping into it (and yes, the "Just My Code" option is not checked). If I put a breakpoint in the method I'm trying to get into, it works fine (as in the debugger will break on the line), but as soon as I step (F10) it exits the method (and with F11 [step into] also). Ok, on first thought, you might think it's to do with the link, but no, it isn't. I tried removing the link and using a copy instead, but the same thing happens. And no, it's not the debug symbols, I looked into that already. The method I'm trying to step through is static, and is in a non-static partial class, in a file shared by both projects. My guess: The same types and static methods exist in the WCF and Silverlight ... would the debugger get confused?

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• Can't combine "LINQ Join" with other tables

  - by FullmetalBoy

  The main problem is that I recieve the following message: "base {System.SystemException} = {"Unable to create a constant value of type 'BokButik1.Models.Book-Author'. Only primitive types ('such as Int32, String, and Guid') are supported in this context."}" based on this LinQ code: IBookRepository myIBookRepository = new BookRepository(); var allBooks = myIBookRepository.HamtaAllaBocker(); IBok_ForfattareRepository myIBok_ForfattareRepository = new Bok_ForfattareRepository(); var Book-Authors = myIBok_ForfattareRepository.HamtaAllaBok_ForfattareNummer(); var q = from booknn in allBooks join Book-Authornn in Book-Authors on booknn.BookID equals Book-Authornn.BookID select new { booknn.title, Book-AuthorID }; How shall I solve this problem to get a class instance that contain with property title and Book-AuthorID? // Fullmetalboy I also have tried making some dummy by using "allbooks" relation with Code Samples from the address http://www.hookedonlinq.com/JoinOperator.ashx. Unfortunately, still same problem. I also have taken account to Int32 due to entity framework http://msdn.microsoft.com/en-us/library/bb896317.aspx. Unfortunatley, still same problem. Using database with 3 tables and one of them is a many to many relationship. This database is used in relation with entity framework Book-Author Book-Author (int) BookID (int) Forfattare (int) Book BookID (int) title (string) etc etc etc

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• std::conditional compile-time branch evaluation

  - by cmannett85

  Compiling this: template < class T, class Y, class ...Args > struct isSame { static constexpr bool value = std::conditional< sizeof...( Args ), typename std::conditional< std::is_same< T, Y >::value, isSame< Y, Args... >, // Error! std::false_type >::type, std::is_same< T, Y > >::type::value; }; int main() { qDebug() << isSame< double, int >::value; return EXIT_SUCCESS; } Gives me this compiler error: error: wrong number of template arguments (1, should be 2 or more) The issue is that isSame< double, int > has an empty Args parameter pack, so isSame< Y, Args... > effectively becomes isSame< Y > which does not match the signature. But my question is: Why is that branch being evaluated at all? sizeof...( Args ) is false, so the inner std:conditional should not be evaluated. This isn't a runtime piece of code, the compiler knows that sizeof..( Args ) will never be true with the given template types. If you're curious, it's supposed to be a variadic version of std::is_same, not that it works...

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• Application Design: Single vs. Multiple Hits to the DB

  - by shyneman

  I'm building a service that performs a set of configured activities based on the type of request that it receives. Each activity involves going to the database and retrieving/updating some kind of information. The logic for each activity can be generalized and re-used across different request types. The activities may need to participate in a transaction for the duration of the servicing the request. One option, I'm considering is having each activity maintain its own access to DAL/database. This fully encapsulates the activity into a stand-alone re-usable piece, but hitting the database multiple times for one request doesn't seem like a viable option. I don't really know how to easily implement the concept of a transaction across the multiple activities here either. The second option is to encapsulate ALL the activities into one big activity and hit the database once. But this does not allow re-use and configuration of these activities for different requests. Does anyone have any suggestions and input about what should be the best way to approach my problem? Thanks for any help.

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• Entity Framework: Auto-updating foreign key when setting a new object reference

  - by Adrian Grigore

  Hi, I am porting an existing application from Linq to SQL to Entity Framework 4 (default code generation). One difference I noticed between the two is that a foreign key property are not updated when resetting the object reference. Now I need to decide how to deal with this. For example supposing you have two entity types, Company and Employee. One Company has many Employees. In Linq To SQL, setting the company also sets the company id: var company=new Company(ID=1); var employee=new Employee(); Debug.Assert(employee.CompanyID==0); employee.Company=company; Debug.Assert(employee.CompanyID==1); //Works fine! In Entity Framework (and without using any code template customization) this does not work: var company=new Company(ID=1); var employee=new Employee(); Debug.Assert(employee.CompanyID==0); employee.Company=company; Debug.Assert(employee.CompanyID==1); //Throws, since CompanyID was not updated! How can I make EF behave the same way as LinqToSQL? I had a look at the default code generation T4 template, but I could not figure out how to make the necessary changes.

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• how to store/model users/faceboook users/linkedin users, etc, with ActiveRecord?

  - by crankharder

  My app has "normal" users: those which come through a typical signup page facebook(FB) users: those which come from Facebook connect "FB-normal" users: a user that can log with both email/password * FB connect Further, there's the a slew of other openID-ish login methods (I don't think openID itself will be acceptable since it doesn't link up the accounts and allow the 3rd party specific features (posting to twitter, adding a FB post, etc etc)) So, how do I model this? Right now we have User class with #facebook_user? defined -- but it gets messy with the "FB-normal" users - plus all the validations become very tricky and hard to interpret. Also, there are methods like #deliver_password_reset! which make no sense in the context for facebook-only users. (this is lame) I've thought out STI (User::Facebook, User::Normal, User::FBNormal, etc.) This makes validations super slick, but it doesn't scale to other connection types, and all the permutations between them... User::FacebookLinkedInNormal(wtf?) Doing this with a bunch of modules I think would suck a lot. Any other ideas?

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• F# numeric associations

  - by b1g3ar5

  I have a numeric association for a custom type as follows: let DiffNumerics = { new INumeric<Diff> with member op.Zero = C 0.0 member op.One = C 1.0 member op.Add(a,b) = a + b member op.Subtract(a,b) = a - b member op.Multiply(a,b) = a * b member ops.Negate(a) = Diff.negate a member ops.Abs(a) = Diff.abs a member ops.Equals(a, b) = ((=) a b) member ops.Compare(a, b) = Diff.compare a b member ops.Sign(a) = int (Diff.sign a).Val member ops.ToString(x,fmt,fmtprovider) = failwith "not implemented" member ops.Parse(s,numstyle,fmtprovider) = failwith "not implemented" } GlobalAssociations.RegisterNumericAssociation(DiffNumerics) It works fine in f# interactive, but crashes when I run, because .ElementOps is not filled correctly for a matrix of these types. Any ideas why this might be? EDIT: In fsi, the code let A = dmatrix [[Diff.C 1.;Diff.C 2.;Diff.C 3.];[Diff.C 4.;Diff.C 5.;Diff.C 6.]] let B = matrix [[1.;2.;3.];[4.;5.;6.]] gives: > A.ElementOps;; val it : INumeric<Diff> = FSI_0003.NewAD+DiffNumerics@258 > B.ElementOps;; val it : INumeric<float> = Microsoft.FSharp.Math.Instances+FloatNumerics@115 > in the debugger A.ElementOps shows: '(A).ElementOps' threw an exception of type 'System.NotSupportedException' and, for the B matrix: Microsoft.FSharp.Math.Instances+FloatNumerics@115 So somehow the DiffNumerics isn't making it to the compiled program.

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• What OOP pattern to use when only adding new methods, not data?

  - by Jonathon Reinhart

  Hello eveyone... In my app, I have deal with several different "parameters", which derive from IParameter interface, and also ParamBase abstract base class. I currently have two different parameter types, call them FooParameter and BarParameter, which both derive from ParamBase. Obviously, I can treat them both as IParameters when I need to deal with them generically, or detect their specific type when I need to handle their specific functionality. My question lies in specific FooParameters. I currently have a few specific ones with their own classes which derive from FooParameter, we'll call them FP12, FP13, FP14, etc. These all have certain characteristics, which make me treat them differently in the UI. (Most have names associated with the individual bits, or ranges of bits). Note that these specific, derived FP's have no additional data associated with them, only properties (which refer to the same data in different ways) or methods. Now, I'd like to keep all of these parameters in a Dictionary<String, IParameter> for easy generic access. The problem is, if I want to refer to a specific one with the special GUI functions, I can't write: FP12 fp12 = (FP12)paramList["FP12"] because you can't downcast to a derived type (rightfully so). But in my case, I didn't add any data, so the cast would theoretically work. What type of programming model should I be using instead? Thanks!

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