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• Detecting 'stealth' web-crawlers

  - by Jacco

  What options are there to detect web-crawlers that do not want to be detected? (I know that listing detection techniques will allow the smart stealth-crawler programmer to make a better spider, but I do not think that we will ever be able to block smart stealth-crawlers anyway, only the ones that make mistakes.) I'm not talking about the nice crawlers such as googlebot and Yahoo! Slurp. I consider a bot nice if it: identifies itself as a bot in the user agent string reads robots.txt (and obeys it) I'm talking about the bad crawlers, hiding behind common user agents, using my bandwidth and never giving me anything in return. There are some trapdoors that can be constructed updated list (thanks Chris, gs): Adding a directory only listed (marked as disallow) in the robots.txt, Adding invisible links (possibly marked as rel="nofollow"?), style="display: none;" on link or parent container placed underneath another element with higher z-index detect who doesn't understand CaPiTaLiSaTioN, detect who tries to post replies but always fail the Captcha. detect GET requests to POST-only resources detect interval between requests detect order of pages requested detect who (consistently) requests https resources over http detect who does not request image file (this in combination with a list of user-agents of known image capable browsers works surprisingly nice) Some traps would be triggered by both 'good' and 'bad' bots. you could combine those with a whitelist: It trigger a trap It request robots.txt? It doest not trigger another trap because it obeyed robots.txt One other important thing here is: Please consider blind people using a screen readers: give people a way to contact you, or solve a (non-image) Captcha to continue browsing. What methods are there to automatically detect the web crawlers trying to mask themselves as normal human visitors. Update The question is not: How do I catch every crawler. The question is: How can I maximize the chance of detecting a crawler. Some spiders are really good, and actually parse and understand html, xhtml, css javascript, VB script etc... I have no illusions: I won't be able to beat them. You would however be surprised how stupid some crawlers are. With the best example of stupidity (in my opinion) being: cast all URLs to lower case before requesting them. And then there is a whole bunch of crawlers that are just 'not good enough' to avoid the various trapdoors.

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• Access Violation Using memcpy or Assignment to an Array in a Struct

  - by Synetech inc.

  Hi, I wrote a program last night that worked just fine but when I refactored it today to make it more extensible, I ended up with a problem. The original version had a hard-coded array of bytes. After some processing, some bytes were written into the array and then some more processing was done. To avoid hard-coding the pattern, I put the array in a structure so that I could add some related data and create an array of them. However now, I cannot write to the array in the structure. Here’s a pseudo-code example: main() { char pattern[]="\x32\x33\x12\x13\xba\xbb"; PrintData(pattern); pattern[2]='\x65'; PrintData(pattern); } That one works but this one does not: struct ENTRY { char* pattern; int somenum; }; main() { ENTRY Entries[] = { {"\x32\x33\x12\x13\xba\xbb\x9a\xbc", 44} , {"\x12\x34\x56\x78", 555} }; PrintData(Entries[0].pattern); Entries[0].pattern[2]='\x65'; //0xC0000005 exception!!! :( PrintData(Entries[0].pattern); } The second version causes an access violation exception on the assignment. I’m sure it’s because the second version allocates memory differently, but I’m starting to get a headache trying to figure out what’s what or how to get fix this. (I’m currently working around it by dynamically allocating a buffer of the same size as the pattern array, copying the pattern to the new buffer, making the changes to the buffer, using the buffer in the place of the pattern array, and then trying to remember to free the—temporary—buffer.) (Specifically, the original version cast the pattern array—+offset—to a DWORD* and assigned a DWORD constant to it to overwrite the four target bytes. The new version cannot do that since the length of the source is unknown—may not be four bytes—so it uses memcpy instead. I’ve checked and re-checked and have made sure that the pointers to memcpy are correct, but I still get an access violation. I use memcpy instead of str(n)cpy because I am using plain chars (as an array of bytes), not Unicode chars and ignoring the null-terminator. Using an assignment as above causes the same problem.) Any ideas? Thanks a lot.

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• sqlite3-ruby can't make on rvm 1.8.7

  - by Josh Crews

  Upgrading to Rails 3 by starting with RVM 1.8.7. OSX 10.5.8 Output: josh-crewss-macbook:~ joshcrews$ gem install sqlite3-rubyBuilding native extensions. This could take a while...ERROR: Error installing sqlite3-ruby: ERROR: Failed to build gem native extension. /Users/joshcrews/.rvm/rubies/ruby-1.8.7-p174/bin/ruby extconf.rb checking for sqlite3.h... yes checking for sqlite3_libversion_number() in -lsqlite3... yes checking for rb_proc_arity()... no checking for sqlite3_column_database_name()... no checking for sqlite3_enable_load_extension()... no checking for sqlite3_load_extension()... no creating Makefile make gcc -I. -I. -I/Users/joshcrews/.rvm/rubies/ruby-1.8.7-p174/lib/ruby/1.8/i686-darwin9.8.0 -I. -I/usr/local/include -I/opt/local/include -I/usr/include -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -fno-common -g -O2 -fno-common -pipe -fno-common -O3 -Wall -Wcast-qual -Wwrite-strings -Wconversion -Wmissing-noreturn -Winline -c database.c database.c: In function ‘deallocate’: database.c:17: warning: implicit declaration of function ‘sqlite3_next_stmt’ database.c:17: warning: assignment makes pointer from integer without a cast database.c: In function ‘initialize’: database.c:76: warning: implicit declaration of function ‘sqlite3_open_v2’ database.c:79: error: ‘SQLITE_OPEN_READWRITE’ undeclared (first use in this function) database.c:79: error: (Each undeclared identifier is reported only once database.c:79: error: for each function it appears in.) database.c:79: error: ‘SQLITE_OPEN_CREATE’ undeclared (first use in this function) database.c: In function ‘set_sqlite3_func_result’: database.c:277: error: ‘sqlite3_int64’ undeclared (first use in this function) database.c: In function ‘rb_sqlite3_func’: database.c:311: warning: passing argument 1 of ‘ruby_xcalloc’ as signed due to prototype database.c: In function ‘rb_sqlite3_step’: database.c:378: warning: passing argument 1 of ‘ruby_xcalloc’ as signed due to prototype make: *** [database.o] Error 1 Gem list (these are under RVM, under system I've got lot more gems included the sqlite3-ruby that's worked for 1.5 years) josh-crewss-macbook:~ joshcrews$ gem list *** LOCAL GEMS *** abstract (1.0.0) actionmailer (3.0.0.beta3) actionpack (3.0.0.beta3) activemodel (3.0.0.beta3) activerecord (3.0.0.beta3) activeresource (3.0.0.beta3) activesupport (3.0.0.beta3, 2.3.8) arel (0.3.3) builder (2.1.2) bundler (0.9.25) capybara (0.3.8) configuration (1.1.0) cucumber (0.7.2) cucumber-rails (0.3.1) culerity (0.2.10) database_cleaner (0.5.2) diff-lcs (1.1.2) erubis (2.6.5) ffi (0.6.3) gherkin (1.0.30) i18n (0.4.0, 0.3.7) json_pure (1.4.3) launchy (0.3.5) mail (2.2.1) memcache-client (1.8.3) mime-types (1.16) nokogiri (1.4.2) polyglot (0.3.1) rack (1.1.0) rack-mount (0.6.3) rack-test (0.5.4) rails (3.0.0.beta3) railties (3.0.0.beta3) rake (0.8.7) rdoc (2.5.8) rspec (2.0.0.beta.10, 2.0.0.beta.8) rspec-core (2.0.0.beta.10, 2.0.0.beta.8) rspec-expectations (2.0.0.beta.10, 2.0.0.beta.8) rspec-mocks (2.0.0.beta.10, 2.0.0.beta.8) rspec-rails (2.0.0.beta.10, 2.0.0.beta.8) rubygems-update (1.3.7) selenium-webdriver (0.0.20) spork (0.8.3) term-ansicolor (1.0.5) text-format (1.0.0) text-hyphen (1.0.0) thor (0.13.6) treetop (1.4.8) trollop (1.16.2) tzinfo (0.3.22) webrat (0.7.1) Version of XCode: 3.1.1 My suspicion is it has to do with "-I/Users/joshcrews/.rvm/rubies/ruby-1.8.7-p174/lib/ruby/1.8/i686-darwin9.8.0", because i686-darwin9.8.0 doesnt exist in that file

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• Linq to List and IEnumerable issues

  - by Otaku

  I am querying an HTML file with Linq. It looks something like this: <html> <body> <div class="Players"> <div class="role">Goalies</div> <div class="name">John Smith</div> <div class="name">Shawn Xie</div> <div class="role">Right Wings</div> <div class="name">Jack Davis</div> <div class="name">Carl Yuns</div> <div class="name">Wayne Gortonia</div> <div class="role">Centers</div> <div class="name">Lutz Gaspy</div> <div class="name">John Jacobs</div> </div </html> </body> What I'm trying to do is create a list of these folks like in a list of a structure called Players: Structure Players Public Name As String Public Position As String End Structure But I've quickly found out I don't really know what I'm doing when it comes to Linq. I've got this far my my queries: Dim goalieList = From d In player.Elements _ Where d.Value = "Goalies" _ Select From g In d.ElementsAfterSelf _ Take While (g.@class <> "role") _ Select New Players With {.Position = "Goalie", _ .Name = g.Value} Dim centersList = From d In player.Elements _ Where d.Value = "Centers" _ Select From g In d.ElementsAfterSelf _ Take While (g.@class <> "role") _ Select New Players With {.Position = "Centers", _ .Name = g.Value} Which gets me down to the the players by position, but then I can't do much with this afterwards the result type is System.Collections.Generic.IEnumerable(Of System.Collections.Generic.IEnumerable(Of Player)) What I want to do is add these two results to a new list, like: Dim playersList As List(Of Players) = Nothing playersList.AddRange(centersList) playersList.AddRange(goalieList) So that I can then query the list and use it. But it kicks the error: Unable to cast object of type 'WhereSelectEnumerableIterator2[System.Xml.Linq.XElement,System.Collections.Generic.IEnumerable1[Players]]' to type 'System.Collections.Generic.IEnumerable`1[Players]' As you can see, I may really have no idea how to work with all these objects/classes. Does anyone have any insight on what I may be doing wrong and how I can resolve it? RESOLVED: The Linq query needs to return a single iEnumerable, like this: Dim goalieList = From l In _ (From d In players.Elements _ Where d.Value = "Goalies" _ Select d.ElementsAfterSelf.TakeWhile(Function(f) f.@class <> "role")) _ Select New Players With {.Position = "Goalie", .Name = l.Value} and then use goalieList.ToList

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• QueryInterface fails at casting inside COM-interface implementation

  - by brecht

  I am creating a tool in c# to retrieve messages of a CAN-network (network in a car) using an Dll written in C/C++. This dll is usable as a COM-interface. My c#-formclass implements one of these COM-interfaces. And other variables are instantiated using these COM-interfaces (everything works perfect). The problem: The interface my C#-form implements has 3 abstract functions. One of these functions is called -by the dll- and i need to implement it myself. In this function i wish to retrieve a property of a form-wide variable that is of a COM-type. The COM library is CANSUPPORTLib The form-wide variable: private CANSUPPORTLib.ICanIOEx devices = new CANSUPPORTLib.CanIO(); This variable is also form-wide and is retrieved via the devices-variable: canreceiver = (CANSUPPORTLib.IDirectCAN2)devices.get_DirectDispatch(receiverLogicalChannel); The function that is called by the dll and implemented in c# public void Message(double dTimeStamp) { Console.WriteLine("!!! message ontvangen !!!" + Environment.NewLine); try { CANSUPPORTLib.can_msg_tag message = new CANSUPPORTLib.can_msg_tag(); message = (CANSUPPORTLib.can_msg_tag) System.Runtime.InteropServices.Marshal.PtrToStructure(canreceiver.RawMessage, message.GetType()); for (int i = 0; i < message.data.Length; i++) { Console.WriteLine("byte " + i + ": " + message.data[i]); } } catch (Exception e) { Console.WriteLine(e.Message); } } The error rises at this line: message = (CANSUPPORTLib.can_msg_tag)System.Runtime.InteropServices.Marshal.PtrToStructure(canreceiver.RawMessage, message.GetType()); Error: Unable to cast COM object of type 'System.__ComObject' to interface type 'CANSUPPORTLib.IDirectCAN2'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{33373EFC-DB42-48C4-A719-3730B7F228B5}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)). Notes: It is possible to have a timer-clock that checks every 100ms for the message i need. The message is then retrieved in the exact same way as i do now. This timer is started when the form starts. The checking is only done when Message(double) has put a variable to true (a message arrived). When the timer-clock is started in the Message function, i have the same error as above Starting another thread when the form starts, is also not possible. Is there someone with experience with COM-interop ? When this timer

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• gwt-RPC problem! what is the best practice on using gwt-RPC?

  - by guaz

  Dear all, I want draw a chart based on the date retrieve from the database by using RPC. But everytime I fail to get the result. My rpc function is working. I think is the sequence of the process. below is my class: public class TrafficPattern_1 extends GChart { TrafficPattern_1() { final DBServiceAsync dbService = GWT .create(DBService.class); dbService.SendData(null, null, new AsyncCallback<Container_TrafficPattern>() { @Override public void onFailure(Throwable caught) { } @Override public void onSuccess(Container_TrafficPattern result) { // TODO Auto-generated method stub pContainer.SetaDate(result.aDate.get(1)); } }); pContainer.aDate.get(0); setChartSize(350, 200); setChartTitle("<h2>Temperature vs Time<h2>"); setPadding("8px"); //setPixelSize(380, 200); getXAxis().setAxisLabel("<small><b><i>Time</i></b></small>"); getXAxis().setHasGridlines(true); getXAxis().setTickCount(6); // Except for "=(Date)", a standard GWT DateTimeFormat string getXAxis().setTickLabelFormat("=(Date)h:mm a"); getYAxis().setAxisLabel("<small><b><i>&deg;C</i></b></small>"); getYAxis().setHasGridlines(true); getYAxis().setTickCount(11); getYAxis().setAxisMin(11); getYAxis().setAxisMax(16); addCurve(); getCurve().setLegendLabel("<i> </i>"); getCurve().getSymbol().setBorderColor("blue"); getCurve().getSymbol().setBackgroundColor("blue"); // getCurve().getSymbol().setFillSpacing(10); // getCurve().getSymbol().setFillThickness(3); getCurve().getSymbol().setSymbolType(SymbolType.LINE); getCurve().getSymbol().setFillThickness(2); getCurve().getSymbol().setFillSpacing(1); for (int i = 0; i < dateSequence.length; i++) // Note that getTime() returns milliseconds since // 1/1/70--required whenever "date cast" tick label // formats (those beginning with "=(Date)") are used. getCurve().addPoint(dateSequence[i].date.getTime(), dateSequence[i].value); }

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• Chaining IQueryables together

  - by Matt Greer

  I have a RIA Services based app that is using Entity Framework on the server side (possibly not relevant). In my real app, I can do something like this. EntityQuery<Status> query = statusContext.GetStatusesQuery().Where(s => s.Description.Contains("Foo")); Where statusContext is the client side subclass of DomainContext that RIA Services was kind enough to generate for me. The end result is an EntityQuery<Status> object who's Query property is an object that implements IQueryable and represents my where clause. The WebDomainClient is able to take this EntityQuery and not just give me back all of my Statuses but also filtered with my where clause. I am trying to implement this in a mock DomainClient. This MockDomainClient accepts an IQueryably<Entity> which it returns when asked for. But what if the user makes the query and includes the ad hoc additional query? How can I merge the two together? My MockDomainClient is (this is modeled after this blog post) ... public class MockDomainClient : LocalDomainClient { private IQueryable<Entity> _entities; public MockDomainClient(IQueryable<Entity> entities) { _entities = entities; } public override IQueryable<Entity> DoQuery(EntityQuery query) { if (query.Query == null) { return _entities; } // otherwise want the union of _entities and query.Query, query.Query is IQueryable // the below does not work and was a total shot in the dark: //return _entities.Union(query.Query.Cast<Entity>()); } } public abstract class LocalDomainClient : System.ServiceModel.DomainServices.Client.DomainClient { private SynchronizationContext _syncContext; protected LocalDomainClient() { _syncContext = SynchronizationContext.Current; } ... public abstract IQueryable<Entity> DoQuery(EntityQuery query); protected override IAsyncResult BeginQueryCore(EntityQuery query, AsyncCallback callback, object userState) { IQueryable<Entity> localQuery = DoQuery(query); LocalAsyncResult asyncResult = new LocalAsyncResult(callback, userState, localQuery); _syncContext.Post(o => (o as LocalAsyncResult).Complete(), asyncResult); return asyncResult; } ... }

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• Handling Model Inheritance in ASP.NET MVC2 & NHibernate

  - by enth

  I've gotten myself stuck on how to handle inheritance in my model when it comes to my controllers/views. Basic Model: public class Procedure : Entity { public Procedure() { } public int Id { get; set; } public DateTime ProcedureDate { get; set; } public ProcedureType Type { get; set; } } public ProcedureA : Procedure { public double VariableA { get; set; } public int VariableB { get; set; } public int Total { get; set; } } public ProcedureB : Procedure { public int Score { get; set; } } etc... many of different procedures eventually. So, I do things like list all the procedures: public class ProcedureController : Controller { public virtual ActionResult List() { IEnumerable<Procedure> procedures = _repository.GetAll(); return View(procedures); } } but now I'm kinda stuck. Basically, from the list page, I need to link to pages where the specific subclass details can be viewed/edited and I'm not sure what the best strategy is. I thought I could add an action on the ProcedureController that would conjure up the right subclass by dynamically figuring out what repository to use and loading the subclass to pass to the view. I had to store the class in the ProcedureType object. I had to create/implement a non-generic IRepository since I can't dynamically cast to a generic one. public virtual ActionResult Details(int procedureID) { Procedure procedure = _repository.GetById(procedureID, false); string className = procedure.Type.Class; Type type = Type.GetType(className, true); Type repositoryType = typeof (IRepository<>).MakeGenericType(type); var repository = (IRepository)DependencyRegistrar.Resolve(repositoryType); Entity procedure = repository.GetById(procedureID, false); return View(procedure); } I haven't even started sorting out how the view is going to determine which partial to load to display the subclass details. I'm wondering if this is a good approach? This makes determining the URL easy. It makes reusing the Procedure display code easy. Another approach is specific controllers for each subclass. It simplifies the controller code, but also means many simple controllers for the many procedure subclasses. Can work out the shared Procedure details with a partial view. How to get to construct the URL to get to the controller/action in the first place? Time to not think about it. Hopefully someone can show me the light. Thanks in advance.

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• Reflection - SetValue of array within class?

  - by Jaymz87

  OK, I've been working on something for a while now, using reflection to accomplish a lot of what I need to do, but I've hit a bit of a stumbling block... I'm trying to use reflection to populate the properties of an array of a child property... not sure that's clear, so it's probably best explained in code: Parent Class: Public Class parent Private _child As childObject() Public Property child As childObject() Get Return _child End Get Set(ByVal value As child()) _child = value End Set End Property End Class Child Class: Public Class childObject Private _name As String Public Property name As String Get Return _name End Get Set(ByVal value As String) _name = value End Set End Property Private _descr As String Public Property descr As String Get Return _descr End Get Set(ByVal value As String) _descr = value End Set End Property End Class So, using reflection, I'm trying to set the values of the array of child objects through the parent object... I've tried several methods... the following is pretty much what I've got at the moment (I've added sample data just to keep things simple): Dim Results(1) As String Results(0) = "1,2" Results(1) = "2,3" Dim parent As New parent Dim child As childObject() = New childObject() {} Dim PropInfo As PropertyInfo() = child.GetType().GetProperties() Dim i As Integer = 0 For Each res As String In Results Dim ResultSet As String() = res.Split(",") ReDim child(i) Dim j As Integer = 0 For Each PropItem As PropertyInfo In PropInfo PropItem.SetValue(child, ResultSet(j), Nothing) j += 1 Next i += 1 Next parent.child = child This fails miserably on PropItem.SetValue with ArgumentException: Property set method not found. Anyone have any ideas? @Jon :- Thanks, I think I've gotten a little further, by creating individual child objects, and then assigning them to an array... The issue is now trying to get that array assigned to the parent object (using reflection). It shouldn't be difficult, but I think the problem comes because I don't necessarily know the parent/child types. I'm using reflection to determine which parent/child is being passed in. The parent always has only one property, which is an array of the child object. When I try assigning the child array to the parent object, I get a invalid cast exception saying it can't convert Object[] to . EDIT: Basically, what I have now is: Dim PropChildInfo As PropertyInfo() = ResponseObject.GetType().GetProperties() For Each PropItem As PropertyInfo In PropChildInfo PropItem.SetValue(ResponseObject, ResponseChildren, Nothing) Next ResponseObject is an instance of the parent Class, and ResponseChildren is an array of the childObject Class. This fails with: Object of type 'System.Object[]' cannot be converted to type 'childObject[]'.

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• DynamicMethod for ConstructorInfo.Invoke, what do I need to consider?

  - by Lasse V. Karlsen

  My question is this: If I'm going to build a DynamicMethod object, corresponding to a ConstructorInfo.Invoke call, what types of IL do I need to implement in order to cope with all (or most) types of arguments, when I can guarantee that the right type and number of arguments is going to be passed in before I make the call? Background I am on my 3rd iteration of my IoC container, and currently doing some profiling to figure out if there are any areas where I can easily shave off large amounts of time being used. One thing I noticed is that when resolving to a concrete type, ultimately I end up with a constructor being called, using ConstructorInfo.Invoke, passing in an array of arguments that I've worked out. What I noticed is that the invoke method has quite a bit of overhead, and I'm wondering if most of this is just different implementations of the same checks I do. For instance, due to the constructor matching code I have, to find a matching constructor for the predefined parameter names, types, and values that I have passed in, there's no way this particular invoke call will not end up with something it should be able to cope with, like the correct number of arguments, in the right order, of the right type, and with appropriate values. When doing a profiling session containing a million calls to my resolve method, and then replacing it with a DynamicMethod implementation that mimics the Invoke call, the profiling timings was like this: ConstructorInfo.Invoke: 1973ms DynamicMethod: 93ms This accounts for around 20% of the total runtime of this profiling application. In other words, by replacing the ConstructorInfo.Invoke call with a DynamicMethod that does the same, I am able to shave off 20% runtime when dealing with basic factory-scoped services (ie. all resolution calls end up with a constructor call). I think this is fairly substantial, and warrants a closer look at how much work it would be to build a stable DynamicMethod generator for constructors in this context. So, the dynamic method would take in an object array, and return the constructed object, and I already know the ConstructorInfo object in question. Therefore, it looks like the dynamic method would be made up of the following IL: l001: ldarg.0 ; the object array containing the arguments l002: ldc.i4.0 ; the index of the first argument l003: ldelem.ref ; get the value of the first argument l004: castclass T ; cast to the right type of argument (only if not "Object") (repeat l001-l004 for all parameters, l004 only for non-Object types, varying l002 constant from 0 and up for each index) l005: newobj ci ; call the constructor l006: ret Is there anything else I need to consider? Note that I'm aware that creating dynamic methods will probably not be available when running the application in "reduced access mode" (sometimes the brain just won't give up those terms), but in that case I can easily detect that and just calling the original constructor as before, with the overhead and all.

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• Jini : single server with multiple clients

  - by user200340

  Hi all, I have a question about how to make multiple clients can access a single file located on server side and keep the file consistent. I have a simple PhoneBook server-client Jini program running at the moment, and server only provides some getter functions to clients, such as getName(String number), getNumber(String name) from a PhoneBook class(serializable), phonebook data are stored in a text file (phonebook.txt) at the moment. I have tried to implement some functions allowing to write a new records into the phonebook.txt file. If the writing record (name) is existing, an integer number will be added into the writing record. for example the existing phonebook.txt is .... John 01-01010101 .... if the writing record is "John 01-12345678",then "John_1 01-12345678" will be writen into phonebook.txt However, if i start with two clients A and B (on the same machine using localhost), and A tries to write "John 01-11111111", B tries to write "John 01-22222222". The early record will be overwritten later record. So, there must be something i did complete wrong. My client and server code are just like Jini HelloWorld example. My server side code is . 1. LookupDiscovery with parameter new String[]{""}; 2. DiscoveryListener for LookupDiscovery 3. registrations are saved into a HashTable 4. for every discovered lookup service, i use registrar to register the ServiceItem, ServiceItem contains a null attributeSets, a null serviceId, and a service. The client code has: 1. LookupDiscovery with parameter new String[]{""}; 2. DiscoveryListener for LookupDiscovery 3. a ServiceTemplate with null attributeSets, a null serviceId and a type, the type is the interface class. 4. for each found ServiceRegistrar, if it can find the looking for ServiceTemplate, the returned Object is cast into the type of the interface class. I have tried to google more details, and i found JavaSpace could be the one i missed. But i am still not sure about it (i only start Jini for a very short time). So any help would be greatly appreciated.

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• WPF: Binding to ObservableCollection in ControlTemplate is not updated

  - by Julian Lettner

  I created a ControlTemplate for my custom control MyControl. MyControl derives from System.Windows.Controls.Control and defines the following property public ObservableCollection<MyControl> Children{ get; protected set; }. To display the nested child controls I am using an ItemsControl (StackPanel) which is surrounded by a GroupBox. If there are no child controls, I want to hide the GroupBox. Everything works fine on application startup: The group box and child controls are shown if the Children property initially contained at least one element. In the other case it is hidden. The problem starts when the user adds a child control to an empty collection. The GroupBox's visibility is still collapsed. The same problem occurs when the last child control is removed from the collection. The GroupBox is still visible. Another symptom is that the HideEmptyEnumerationConverter converter does not get called. Adding/removing child controls to non empty collections works as expected. Whats wrong with the following binding? Obviously it works once but does not get updated, although the collection I am binding to is of type ObservableCollection. <!-- Converter for hiding empty enumerations --> <Common:HideEmptyEnumerationConverter x:Key="hideEmptyEnumerationConverter"/> <!--- ... ---> <ControlTemplate TargetType="{x:Type MyControl}"> <!-- ... other stuff that works ... --> <!-- Child components --> <GroupBox Header="Children" Visibility="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Children, Converter={StaticResource hideEmptyEnumerationConverter}}"> <ItemsControl ItemsSource="{TemplateBinding Children}"/> </GroupBox> </ControlTemplate> . [ValueConversion(typeof (IEnumerable), typeof (Visibility))] public class HideEmptyEnumerationConverter : IValueConverter { #region IValueConverter Members public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { int itemCount = ((IEnumerable) value).Cast<object>().Count(); return itemCount == 0 ? Visibility.Collapsed : Visibility.Visible; } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { throw new NotImplementedException(); } #endregion } Another, more general question: How do you guys debug bindings? Found this (http://bea.stollnitz.com/blog/?p=52) but still I find it very hard to do. I am glad for any help or suggestion.

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• For a .NET winforms datagridview I would like a combobox column to have a different set of values for each row.

  - by Seth Spearman

  Hello, I have a DataGridView that I am binding to a POCO. I have the databinding working fine. However, I have added a combobox column that I want to be different for each row. Specifically, I have a grid of purchased items, some of which have sizes (like Adult XL, Adult L) and other items are not sized (like Car Magnet.) So essentially what I want to change is the DATA SOURCE for a combobox column in the data grid. Can that be done? What event can I hook into that would allow me to change properties of certain columns FOR EACH ROW? An acceptable alternative is to change a property when the user clicks or tabs into the row. What event is that? Seth EDIT I need more help with this question. With Triduses help I am SO close but I need a bit more information. First, per the question, is the CellFormatting event really the best/only event for changing the DataSource for a combo box column. I ask because I am doing something rather resource/data intensive, not merely formatting the cell. Second, the cellformatting event is being called just by having the mouse hover over the cell. I tried to set the FormattingApplied property inside my if-block and then I check for it in the if- test but that is returning a weird error message. My ideal situation is that I would apply change the data source for the combo box once for each row and then be done with it. Finally, in order to set the data source of the combobox colunm I have to be able to cast the Cell inside my if block to a type of DataGridViewComboBoxColumn so that I can fill it with rows or set the datasource or something. Here is the code I have right now. Private Sub ProductsDataGrid_CellFormatting(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellFormattingEventArgs) Handles ProductsDataGrid.CellFormatting If e.ColumnIndex = ProductsDataGrid.Columns("SizeDGColumn").Index Then ' AndAlso Not e.FormattingApplied Then Dim product As LeagueOrderProductInfo = DirectCast(ProductsDataGrid.Rows(e.RowIndex).DataBoundItem, LeagueOrderProductInfo) Dim sizes As LeagueOrderProductSizeList = product.ProductSizes sizes.RemoveSizeFromList(_parentOrderDetail.SizeID) 'WHAT DO I DO HERE TO FILL THE COMBOBOX COLUMN WITH THE sizes collection. End If End Sub Please help. I am completely stuck and this task item should have taken an hour and I am 4+ hours in now. BTW, I am also open to resolving this by taking a completely different direction with it (as long as I can be done quickly.) Seth

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• Linq query challenge

  - by vdh_ant

  My table structure is as follows: Person 1-M PesonAddress Person 1-M PesonPhone Person 1-M PesonEmail Person 1-M Contract Contract M-M Program Contract M-1 Organization At the end of this query I need a populated object graph where each person has their: PesonAddress's PesonPhone's PesonEmail's PesonPhone's Contract's - and this has its respective Program's Now I had the following query and I thought that it was working great, but it has a couple of problems: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") where people.Contract.Any( contract => (param.OrganizationId == contract.OrganizationId) && contract.Program.Any( contractProgram => (param.ProgramId == contractProgram.ProgramId))) select people; The problem is that it filters the person to the criteria but not the Contracts or the Contract's Programs. It brings back all Contracts that each person has not just the ones that have an OrganizationId of x and the same goes for each of those Contract's Programs respectively. What I want is only the people that have at least one contract with an OrgId of x with and where that contract has a Program with the Id of y... and for the object graph that is returned to have only the contracts that match and programs within that contract that match. I kinda understand why its not working, but I don't know how to change it so it is working... This is my attempt thus far: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") let currentContracts = from contract in people.Contract where (param.OrganizationId == contract.OrganizationId) select contract let currentContractPrograms = from contractProgram in currentContracts let temp = from x in contractProgram.Program where (param.ProgramId == contractProgram.ProgramId) select x where temp.Any() select temp where currentContracts.Any() && currentContractPrograms.Any() select new Person { PersonId = people.PersonId, FirstName = people.FirstName, ..., ...., MiddleName = people.MiddleName, Surname = people.Surname, ..., ...., Gender = people.Gender, DateOfBirth = people.DateOfBirth, ..., ...., Contract = currentContracts, ... }; //This doesn't work But this has several problems (where the Person type is an EF object): I am left to do the mapping by myself, which in this case there is quite a lot to map When ever I try to map a list to a property (i.e. Scholarship = currentScholarships) it says I can't because IEnumerable is trying to be cast to EntityCollection Include doesn't work Hence how do I get this to work. Keeping in mind that I am trying to do this as a compiled query so I think that means anonymous types are out.

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• Installing PyGraphViz on Windows, Python 2.7

  - by user574043

  I can't install pygraphviz on Windows XP. I'm using Python27. Before to launch the setup I've changet these two variables of the setup.py file library_path="C:\\Archivos de programa\\Graphviz 2.28\\bin" include_path="C:\\Archivos de programa\\Graphviz 2.28\\include\\graphviz" Then I've launched the setup. I'm using mingw32 as a compiler. I don't know what can I do now. I'm using the following command: C:\Python27\pygraphviz-1.1>c:\python27\python setup.py build -c mingw32 And I've got the folling result library_path=C:\Archivos de programa\Graphviz 2.28\bin include_path=C:\Archivos de programa\Graphviz 2.28\include\graphviz running build running build_py running build_ext building 'pygraphviz._graphviz' extension C:\MinGW\bin\gcc.exe -mno-cygwin -mdll -O -Wall "-IC:\Archivos de programa\Graphviz 2.28\include\graphviz" -Ic:\python27\include -Ic:\python 27\PC -c pygraphviz/graphviz_wrap.c -o build\temp.win32-2.7\Release\pygraphviz\graphviz_wrap.o pygraphviz/graphviz_wrap.c: In function 'agattr_label': pygraphviz/graphviz_wrap.c:2855:5: warning: return makes integer from pointer without a cast writing build\temp.win32-2.7\Release\pygraphviz\_graphviz.def Traceback (most recent call last): File "setup.py", line 146, in <module> package_data = package_data File "c:\python27\lib\distutils\core.py", line 152, in setup dist.run_commands() File "c:\python27\lib\distutils\dist.py", line 953, in run_commands self.run_command(cmd) File "c:\python27\lib\distutils\dist.py", line 972, in run_command cmd_obj.run() File "c:\python27\lib\distutils\command\build.py", line 127, in run self.run_command(cmd_name) File "c:\python27\lib\distutils\cmd.py", line 326, in run_command self.distribution.run_command(command) File "c:\python27\lib\distutils\dist.py", line 972, in run_command cmd_obj.run() File "c:\python27\lib\distutils\command\build_ext.py", line 340, in run self.build_extensions() File "c:\python27\lib\distutils\command\build_ext.py", line 449, in build_extensions self.build_extension(ext) File "c:\python27\lib\distutils\command\build_ext.py", line 531, in build_extension target_lang=language) File "c:\python27\lib\distutils\ccompiler.py", line 741, in link_shared_object extra_preargs, extra_postargs, build_temp, target_lang) File "c:\python27\lib\distutils\cygwinccompiler.py", line 260, in link target_lang) File "c:\python27\lib\distutils\unixccompiler.py", line 218, in link libraries) File "c:\python27\lib\distutils\ccompiler.py", line 1121, in gen_lib_options opt = compiler.runtime_library_dir_option(dir) File "c:\python27\lib\distutils\unixccompiler.py", line 285, in runtime_library_dir_option compiler = os.path.basename(sysconfig.get_config_var("CC")) File "c:\python27\lib\ntpath.py", line 198, in basename return split(p)[1] File "c:\python27\lib\ntpath.py", line 170, in split d, p = splitdrive(p) File "c:\python27\lib\ntpath.py", line 125, in splitdrive if p[1:2] == ':': TypeError: 'NoneType' object is not subscriptable Any idea on how to solve it over windows? In other computer with Ubuntu I've installed without problems.

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• Global Entity Framework Context in WPF Application

  - by OffApps Cory

  Good day, I am in the middle of development of a WPF application that is using Entity Framework (.NET 3.5). It accesses the entities in several places throughout. I am worried about consistency throughout the application in regard to the entities. Should I be instancing separate contexts in my different views, or should I (and is a a good way to do this) instance a single context that can be accessed globally? For instance, my entity model has three sections, Shipments (with child packages and further child contents), Companies/Contacts (with child addresses and telephones), and disk specs. The Shipments and EditShipment views access the DiskSpecs, and the OptionsView manages the DiskSpecs (Create, Edit, Delete). If I edit a DiskSpec, I have to have something in the ShipmentsView to retrieve the latest specs if I have separate contexts right? If it is safe to have one overall context from which the rest of the app retrieves it's objects, then I imagine that is the way to go. If so, where would that instance be put? I am using VB.NET, but I can translate from C# pretty good. Any help would be appreciated. I just don't want one of those applications where the user has to hit reload a dozen times in different parts of the app to get the new data. Update: OK so I have changed my app as follows: All contexts are created in Using Blocks to dispose of them after they are no longer needed. When loaded, all entities are detatched from context before it is disposed. A new property in the MainViewModel (ContextUpdated) raises an event that all of the other ViewModels subscribe to which runs that ViewModels RefreshEntities method. After implementing this, I started getting errors saying that an entity can only be referenced by one ChangeTracker at a time. Since I could not figure out which context was still referencing the entity (shouldn't be any context right?) I cast the object as IEntityWithChangeTracker, and set SetChangeTracker to nothing (Null). This has let to the current problem: When I Null the changeTracker on the Entity, and then attach it to a context, it loses it's changed state and does not get updated to the database. However if I do not null the change tracker, I can't attach. I have my own change tracking code, so that is not a problem. My new question is, how are you supposed to do this. A good example Entity query and entity save code snipped would go a long way, cause I am beating my head in trying to get what I once thought was a simple transaction to work. Any help would elevate you to near god-hood.

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• Linq guru - filtering related entities...

  - by vdh_ant

  My table structure is as follows: Person 1-M PesonAddress Person 1-M PesonPhone Person 1-M PesonEmail Person 1-M Contract Contract M-M Program Contract M-1 Organization At the end of this query I need a populated object graph where each person has their: PesonAddress's PesonPhone's PesonEmail's PesonPhone's Contract's - and this has its respective Program's Now I had the following query and I thought that it was working great, but it has a couple of problems: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") where people.Contract.Any( contract => (param.OrganizationId == contract.OrganizationId) && contract.Program.Any( contractProgram => (param.ProgramId == contractProgram.ProgramId))) select people; The problem is that it filters the person to the criteria but not the Contracts or the Contract's Programs. It brings back all Contracts that each person has not just the ones that have an OrganizationId of x and the same goes for each of those Contract's Programs respectively. What I want is only the people that have at least one contract with an OrgId of x with and where that contract has a Program with the Id of y... and for the object graph that is returned to have only the contracts that match and programs within that contract that match. I kinda understand why its not working, but I don't know how to change it so it is working... This is my attempt thus far: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") let currentContracts = from contract in people.Contract where (param.OrganizationId == contract.OrganizationId) select contract let currentContractPrograms = from contractProgram in currentContracts let temp = from x in contractProgram.Program where (param.ProgramId == contractProgram.ProgramId) select x where temp.Any() select temp where currentContracts.Any() && currentContractPrograms.Any() select new Person { PersonId = people.PersonId, FirstName = people.FirstName, ..., ...., MiddleName = people.MiddleName, Surname = people.Surname, ..., ...., Gender = people.Gender, DateOfBirth = people.DateOfBirth, ..., ...., Contract = currentContracts, ... }; //This doesn't work But this has several problems (where the Person type is an EF object): I am left to do the mapping by myself, which in this case there is quite a lot to map When ever I try to map a list to a property (i.e. Scholarship = currentScholarships) it says I can't because IEnumerable is trying to be cast to EntityCollection Include doesn't work Hence how do I get this to work. Keeping in mind that I am trying to do this as a compiled query so I think that means anonymous types are out.

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• ClassCastException when casting custom View subclass

  - by Jens Jacob

  Hi I've run into an early problem with developing for android. I've made my own custom View (which works well). In the beginning i just added it to the layout programmatically, but i figured i could try putting it into the XML layout instead (for consistency). So what i got is this: main.xml: [...] <sailmeter.gui.CompassView android:id="@+id/compassview1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@id/widget55" android:background="@color/white" /> [...] CompassView.java: public class CompassView extends View { } SailMeter.java (activity class): public class SailMeter extends Activity implements PropertyChangeListener { public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); compassview = (CompassView) findViewById(R.id.compassview1); [...] } } (Theres obviously more, but you get the point) Now, this is the stacktrace: 05-23 16:32:01.991: ERROR/AndroidRuntime(10742): Uncaught handler: thread main exiting due to uncaught exception 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): java.lang.RuntimeException: Unable to start activity ComponentInfo{sailmeter.gui/sailmeter.gui.SailMeter}: java.lang.ClassCastException: android.view.View 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2596) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2621) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at android.app.ActivityThread.access$2200(ActivityThread.java:126) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1932) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at android.os.Handler.dispatchMessage(Handler.java:99) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at android.os.Looper.loop(Looper.java:123) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at android.app.ActivityThread.main(ActivityThread.java:4595) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at java.lang.reflect.Method.invokeNative(Native Method) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at java.lang.reflect.Method.invoke(Method.java:521) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at dalvik.system.NativeStart.main(Native Method) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): Caused by: java.lang.ClassCastException: android.view.View 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at sailmeter.gui.SailMeter.onCreate(SailMeter.java:51) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2544) 05-23 16:32:02.051: ERROR/AndroidRuntime(10742): ... 11 more Why cant i cast my custom view? I need it to be that type since it has a few extra methods in it that i want to access. Should i restructure it and have another class handle the logic, and then just having the view being a view? Thanks for any help.

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• Optimizing multiple dispatch notification algorithm in C#?

  - by Robert Fraser

  Sorry about the title, I couldn't think of a better way to describe the problem. Basically, I'm trying to implement a collision system in a game. I want to be able to register a "collision handler" that handles any collision of two objects (given in either order) that can be cast to particular types. So if Player : Ship : Entity and Laser : Particle : Entity, and handlers for (Ship, Particle) and (Laser, Entity) are registered than for a collision of (Laser, Player), both handlers should be notified, with the arguments in the correct order, and a collision of (Laser, Laser) should notify only the second handler. A code snippet says a thousand words, so here's what I'm doing right now (naieve method): public IObservable<Collision<T1, T2>> onCollisionsOf<T1, T2>() where T1 : Entity where T2 : Entity { Type t1 = typeof(T1); Type t2 = typeof(T2); Subject<Collision<T1, T2>> obs = new Subject<Collision<T1, T2>>(); _onCollisionInternal += delegate(Entity obj1, Entity obj2) { if (t1.IsAssignableFrom(obj1.GetType()) && t2.IsAssignableFrom(obj2.GetType())) obs.OnNext(new Collision<T1, T2>((T1) obj1, (T2) obj2)); else if (t1.IsAssignableFrom(obj2.GetType()) && t2.IsAssignableFrom(obj1.GetType())) obs.OnNext(new Collision<T1, T2>((T1) obj2, (T2) obj1)); }; return obs; } However, this method is quite slow (measurable; I lost ~2 FPS after implementing this), so I'm looking for a way to shave a couple cycles/allocation off this. I thought about (as in, spent an hour implementing then slammed my head against a wall for being such an idiot) a method that put the types in an order based on their hash code, then put them into a dictionary, with each entry being a linked list of handlers for pairs of that type with a boolean indication whether the handler wanted the order of arguments reversed. Unfortunately, this doesn't work for derived types, since if a derived type is passed in, it won't notify a subscriber for the base type. Can anyone think of a way better than checking every type pair (twice) to see if it matches? Thanks, Robert

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• OSGI classcast exception on felix

  - by Nico

  Hi, i'm fairly new to osgi and am trying to get a functional proof of concept together. The setup is that my common api is created in a bundle creatively named common-api.jar with no bundle activator, but it exports all it's interfaces. the one of interest in this situation is DatabaseService.java. I then have a Second bundle called systemx-database-service. That implements the database service interface. this works fine as in the activator of the implementation bundle i test the connection to the database and select some arbitraty values. I also register the service i want to be available to the other bundle's like so: context.registerService(DatabaseService.class.getName(), new SystemDatabaseServiceImpl(context), new Properties()); The basic idea being when you look for a service reference for a Database service you'll get back the SystemDatabaseService implementation. When i do a inspect service the output it this: -> inspect s c 69 System Database Service (69) provides services: ---------------------------------------------- objectClass = za.co.xxx.xxx.common.api.DatabaseService service.id = 39 which would lead me to believe that if i do this in a test bundle: context.getService(context.getServiceReference(DatabaseService.class)); i should get back an instance of DatabaseService.class, but alas no such luck. it simply seems like it cannot find the service. stick with me here my story gets stranger. figuring there is no where to go but up i wrote this monstrosity: for (Bundle bundle : bundles) { if (bundle.getSymbolicName().equals("za.co.xxx.xxx.database-service")) { ServiceReference[] registeredServices = bundle.getRegisteredServices(); for (ServiceReference ref : registeredServices) { DatabaseService service = (DatabaseService) context.getService(ref); // use service here. } } } } now i can actually see the service reference, but i get this error java.lang.ClassCastException: za.co.xxx.xxx.database.service.impl.SystemDatabaseServiceImpl cannot be cast to za.co.xxx.xx.common.api.DatabaseService which is crazy since the implementation clearly implements the interface! Any help would be appreciated. Please keep in mind i'm very new at the osgi way of thinking so my whole approach here might be flawed. oh. if anyone wants the manifests i can post them. and i'm using the maven-bnd-plugin to build and executing on felix. thanks Nico

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• Using Include() with inherited entities problem

  - by Peter Stegnar

  In EF eager loading related entities is easy. But I'm having difficulties including inherited entities when loading data using table-per-type model. This is my model: Entities: ArticleBase (base article entity) ArticleSpecial (inherited from ArticleBase) UserBase (base user entity) UserSpecial (inherited from UserBase) Image Relations are as shown on the image (omitting many columns): In reality my users are always of type UserSpecial, since UserBase is used in another application, thus we can share credentials. That's the only reason I have two separate tables. UserBase table can't be changed in any way shape or form, because the other app would break. Question How am I suppose to load ArticleSpecial with both CreatedBy and EditedBy set, so that both are of type UserSpecial (that defines Image relation)? I've tried (unsuccessfully though) these options: 1. Using lambda expressions: context.ArticleBases .OfType<ArticleSpecial>() .Include("UserCreated.Image") .Include("UserEdited.Image"); In this case the problem is that both CreatedBy and EditedBy are related to UserBase, that doesn't define Image navigation. So I should somehow cast these two to UserSpecial type like: context.ArticleBases .OfType<ArticleSpecial>() .Include("UserCreated<UserSpecial>.Image") .Include("UserEdited<UserSpecial>.Image"); But of course using generics in Include("UserCreated<UserSpecial>.Image") don't work. 2. I have tried using LINQ query var results = from articleSpecial in ctx.ArticleBase.OfType<ArticleSpecial>() join created in ctx.UserBase.OfType<UserSpecial>().Include("Image") on articleSpecial.UserCreated.Id equals created.Id join edited in ctx.UserBase.OfType<UserSpecial>().Include("Image") on articleSpecial.UserEdited.Id equals edited.Id select articleSpecial; In this case I'm only getting ArticleSpecial object instances without related properties being set. I know I should select those somehow, but I don't know how? Select part in my LINQ could be changed to something like select new { articleSpecial, articleSpecial.UserCreated, articleSpecial.UserEdited }; but images are still not loaded into my context. My joins in this case are barely used to filter out articleSpecial results, but they don't load entities into context (I suppose). Can anybody provide any help regarding this problem? I think it's not so uncommon.

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• How to write this Linq SQL as a Dynamic Query (using strings)?

  - by Dr. Zim

  Skip to the "specific question" as needed. Some background: The scenario: I have a set of products with a "drill down" filter (Query Object) populated with DDLs. Each progressive DDL selection will further limit the product list as well as what options are left for the DDLs. For example, selecting a hammer out of tools limits the Product Sizes to only show hammer sizes. Current setup: I created a query object, sent it to a repository, and fed each option to a SQL "table valued function" where null values represent "get all products". I consider this a good effort, but far from DDD acceptable. I want to avoid any "programming" in SQL, hopefully doing everything with a repository. Comments on this topic would be appreciated. Specific question: How would I rewrite this query as a Dynamic Query? A link to something like 101 Linq Examples would be fantastic, but with a Dynamic Query scope. I really want to pass to this method the field in quotes "" for which I want a list of options and how many products have that option. from p in db.Products group p by p.ProductSize into g select new Category { PropertyType = g.Key, Count = g.Count() } Each DDL option will have "The selection (21)" where the (21) is the quantity of products that have that attribute. Upon selecting an option, all other remaining DDLs will update with the remaining options and counts. Edit: Additional notes: .OrderBy("it.City") // "it" refers to the entire record .GroupBy("City", "new(City)") // This produces a unique list of City .Select("it.Count()") //This gives a list of counts... getting closer .Select("key") // Selects a list of unique City .Select("new (key, count() as string)") // +1 to me LOL. key is a row of group .GroupBy("new (City, Manufacturer)", "City") // New = list of fields to group by .GroupBy("City", "new (Manufacturer, Size)") // Second parameter is a projection Product .Where("ProductType == @0", "Maps") .GroupBy("new(City)", "new ( null as string)")// Projection not available later? .Select("new (key.City, it.count() as string)")// GroupBy new makes key an object Product .Where("ProductType == @0", "Maps") .GroupBy("new(City)", "new ( null as string)")// Projection not available later? .Select("new (key.City, it as object)")// the it object is the result of GroupBy var a = Product .Where("ProductType == @0", "Maps") .GroupBy("@0", "it", "City") // This fails to group Product at all .Select("new ( Key, it as Product )"); // "it" is property cast though What I have learned so far is LinqPad is fantastic, but still looking for an answer. Eventually, completely random research like this will prevail I guess. LOL. Edit:

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• Evaluation of CTEs in SQL Server 2005

  - by Jammer

  I have a question about how MS SQL evaluates functions inside CTEs. A couple of searches didn't turn up any results related to this issue, but I apologize if this is common knowledge and I'm just behind the curve. It wouldn't be the first time :-) This query is a simplified (and obviously less dynamic) version of what I'm actually doing, but it does exhibit the problem I'm experiencing. It looks like this: CREATE TABLE #EmployeePool(EmployeeID int, EmployeeRank int); INSERT INTO #EmployeePool(EmployeeID, EmployeeRank) SELECT 42, 1 UNION ALL SELECT 43, 2; DECLARE @NumEmployees int; SELECT @NumEmployees = COUNT(*) FROM #EmployeePool; WITH RandomizedCustomers AS ( SELECT CAST(c.Criteria AS int) AS CustomerID, dbo.fnUtil_Random(@NumEmployees) AS RandomRank FROM dbo.fnUtil_ParseCriteria(@CustomerIDs, 'int') c) SELECT rc.CustomerID, ep.EmployeeID FROM RandomizedCustomers rc JOIN #EmployeePool ep ON ep.EmployeeRank = rc.RandomRank; DROP TABLE #EmployeePool; The following can be assumed about all executions of the above: The result of dbo.fnUtil_Random() is always an int value greater than zero and less than or equal to the argument passed in. Since it's being called above with @NumEmployees which has the value 2, this function always evaluates to 1 or 2. The result of dbo.fnUtil_ParseCriteria(@CustomerIDs, 'int') produces a one-column, one-row table that contains a sql_variant with a base type of 'int' that has the value 219935. Given the above assumptions, it makes sense (to me, anyway) that the result of the expression above should always produce a two-column table containing one record - CustomerID and an EmployeeID. The CustomerID should always be the int value 219935, and the EmployeeID should be either 42 or 43. However, this is not always the case. Sometimes I get the expected single record. Other times I get two records (one for each EmployeeID), and still others I get no records. However, if I replace the RandomizedCustomers CTE with a true temp table, the problem vanishes completely. Every time I think I have an explanation for this behavior, it turns out to not make sense or be impossible, so I literally cannot explain why this would happen. Since the problem does not happen when I replace the CTE with a temp table, I can only assume it has something to do with the functions inside CTEs are evaluated during joins to that CTE. Do any of you have any theories?

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• Qt - Calling widget parent's slots

  - by bullettime

  I wrote a small program to test accessing a widget parent's slot. Basically, it has two classes: Widget: namespace Ui { class Widget; } class Widget : public QWidget { Q_OBJECT public: Widget(QWidget *parent = 0); ~Widget(); QLabel *newlabel; QString foo; public slots: void changeLabel(); private: Ui::Widget *ui; }; Widget::Widget(QWidget *parent) : QWidget(parent), ui(new Ui::Widget) { ui->setupUi(this); customWidget *cwidget = new customWidget(); newlabel = new QLabel("text"); foo = "hello world"; this->ui->formLayout->addWidget(newlabel); this->ui->formLayout->addWidget(cwidget); connect(this->ui->pushButton,SIGNAL(clicked()),cwidget,SLOT(callParentSlot())); connect(this->ui->pb,SIGNAL(clicked()),this,SLOT(changeLabel())); } void Widget::changeLabel(){ newlabel->setText(this->foo); } and customWidget: class customWidget : public QWidget { Q_OBJECT public: customWidget(); QPushButton *customPB; public slots: void callParentSlot(); }; customWidget::customWidget() { customPB = new QPushButton("customPB"); QHBoxLayout *hboxl = new QHBoxLayout(); hboxl->addWidget(customPB); this->setLayout(hboxl); connect(this->customPB,SIGNAL(clicked()),this,SLOT(callParentSlot())); } void customWidget::callParentSlot(){ ((Widget*)this->parentWidget())->changeLabel(); } in the main function, I simply created an instance of Widget, and called show() on it. This Widget instance has a label, a QString, an instance of customWidget class, and two buttons (inside the ui class, pushButton and pb). One of the buttons calls a slot in its own class called changeLabel(), that, as the name suggests, changes the label to whatever is set in the QString contained in it. I made that just to check that changeLabel() worked. This button is working fine. The other button calls a slot in the customWidget instance, named callParentSlot(), that in turn tries to call the changeLabel() slot in its parent. Since in this case I know that its parent is in fact an instance of Widget, I cast the return value of parentWidget() to Widget*. This button crashes the program. I made a button within customWidget to try to call customWidget's parent slot as well, but it also crashes the program. I followed what was on this question. What am I missing?

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• Parse int to string with stringstream

  - by SoulBeaver

  Well! I feel really stupid for this question, and I wholly don't mind if I get downvoted for this, but I guess I wouldn't be posting this if I had not at least made an earnest attempt at looking for the solution. I'm currently working on Euler Problem 4, finding the largest palindromic number of two three-digit numbers [100..999]. As you might guess, I'm at the part where I have to work with the integer I made. I looked up a few sites and saw a few standards for converting an Int to a String, one of which included stringstream. So my code looked like this: // tempTotal is my int value I want converted. void toString( int tempTotal, string &str ) { ostringstream ss; // C++ Standard compliant method. ss << tempTotal; str = ss.str(); // Overwrite referenced value of given string. } and the function calling it was: else { toString( tempTotal, store ); cout << loop1 << " x " << loop2 << "= " << store << endl; } So far, so good. I can't really see an error in what I've written, but the output gives me the address to something. It stays constant, so I don't really know what the program is doing there. Secondly, I tried .ToString(), string.valueOf( tempTotal ), (string)tempTotal, or simply store = temptotal. All refused to work. When I simply tried doing an implicit cast with store = tempTotal, it didn't give me a value at all. When I tried checking output it literally printed nothing. I don't know if anything was copied into my string that simply isn't a printable character, or if the compiler just ignored it. I really don't know. So even though I feel this is a really, really lame question, I just have to ask: How do I convert that stupid integer to a string with the stringstream? The other tries are more or less irrelevant for me, I just really want to know why my stringstream solution isn't working.

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