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• using text and ntext SQL Datatypes in RPG

  - by David Stratton

  I'll preface this with saying that I'm a .NET developer, and am NOT an RPG developer. I'm working with one of our RPG developers to come up with a solution, so any suggestions you provide will get passed to him. We have a scenario where we want our iSeries to read from a SQL Server database. One of the columns is a TEXT column. IN RPG, there is no equivalent data type to use for this. We've gone back and forth on this, and our current plan is to change course, and have our SQL Server write out a text file, which the iSeries can pick up and parse. This is, however, a last resort option, as the data in the file is sensitive, and we'd like to avoid the additional security overhead. We've already got the SQL Server locked down as tight as possible (one user only has read access to this, and that user is an iSeries user.) We don't want to have to worry about transferring files back and forth. However, at this point, we see no other option. We have no in-house Java developers, and need to do this in RPG. So I'm wondering if there are any RPG developers out there who have faced this situation and have any advice.

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• Weird error running com-exposed assembly

  - by Bernabé Panarello

  I am facing the following issue when deploying a com-exposed assembly to my client's. The COM component should be consummed by a vb6 application. Here's how it's done 1) I have one c# project which has a class with a couple of methods exposed to COM 2) The project has references to multiple assemblies 3) I compile the project, generating a folder (named dllcom) that contains the assembly plus all the referenced dlls 4) I include in the folder a .bat which does the following: regasm /u c:\dllcom\LibInsertador.dll del LibInsertador.tlb regasm c:\dllcom\LibInsertador.dll /tlb:c:\dllcom\LibInsertador.tlb /codebase c:\dllcom\ pause 5) After running the bat locally in many workstations of my laboratory, i'm able to consume the generated tlb from my vb6 application without any problems. I'm even able to update the dll by only means of running this bat, without having to recompile the vb6 application. I mean that im not having issues of vb6 fiding and invoking the exposed com object. The problem 6) I send the SAME FOLDER to my client 7) They execute the .bat locally, without any errors 8) They execute the vb6 application, vb6 finds the main assembly, the .net code seems to run correctly (it's even able to generate a log file) until it has to intantiate it's first referenced assembly. Then, they get the following exception: "Could not load type 'GYF.Common.TypeBuilder' from assembly 'GYF_Common, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'." Where "GYF.Common" is an assembly referenced by LibInsertador and TypeBuilder is a class contained in GYF.Common. GYF.Common is not a signed assembly and it's not in the GAC, just in the same folder with Libinsertador. According to .net reflector, the version is correct. ¿Any ideas about what could be happening?

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• Unittesting Url.Action (using Rhino Mocks?)

  - by Kristoffer Ahl

  I'm trying to write a test for an UrlHelper extensionmethod that is used like this: Url.Action<TestController>(x => x.TestAction()); However, I can't seem set it up correctly so that I can create a new UrlHelper and then assert that the returned url was the expected one. This is what I've got but I'm open to anything that does not involve mocking as well. ;O) [Test] public void Should_return_Test_slash_TestAction() { // Arrange RouteTable.Routes.Add("TestRoute", new Route("{controller}/{action}", new MvcRouteHandler())); var mocks = new MockRepository(); var context = mocks.FakeHttpContext(); // the extension from hanselman var helper = new UrlHelper(new RequestContext(context, new RouteData()), RouteTable.Routes); // Act var result = helper.Action<TestController>(x => x.TestAction()); // Assert Assert.That(result, Is.EqualTo("Test/TestAction")); } I tried changing it to urlHelper.Action("Test", "TestAction") but it will fail anyway so I know it is not my extensionmethod that is not working. NUnit returns: NUnit.Framework.AssertionException: Expected string length 15 but was 0. Strings differ at index 0. Expected: "Test/TestAction" But was: <string.Empty> I have verified that the route is registered and working and I am using Hanselmans extension for creating a fake HttpContext. Here's what my UrlHelper extentionmethod look like: public static string Action<TController>(this UrlHelper urlHelper, Expression<Func<TController, object>> actionExpression) where TController : Controller { var controllerName = typeof(TController).GetControllerName(); var actionName = actionExpression.GetActionName(); return urlHelper.Action(actionName, controllerName); } public static string GetControllerName(this Type controllerType) { return controllerType.Name.Replace("Controller", string.Empty); } public static string GetActionName(this LambdaExpression actionExpression) { return ((MethodCallExpression)actionExpression.Body).Method.Name; } Any ideas on what I am missing to get it working??? / Kristoffer

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• DBD::SQLite::st execute failed: datatype mismatch

  - by Barton Chittenden

  Here's a snippit of perl code: sub insert_timesheet { my $dbh = shift; my $entryref = shift; my $insertme = join(',', @_); my $values_template = '?, ' x scalar(@_); chop $values_template; chop $values_template; #remove trailing comma my $insert = "INSERT INTO timesheet( $insertme ) VALUES ( $values_template );"; my $sth = $dbh->prepare($insert); debug("$insert"); my @values; foreach my $entry (@_){ push @values, $$entryref{$entry} } debug("@values"); my $rv = $sth->execute( @values ) or die $dbh->errstr; debug("sql return value: $rv"); $dbh->disconnect; } The value of $insert: [INSERT INTO timesheet( idx,Start_Time,End_Time,Project,Ticket_Number,Site,Duration,Notes ) VALUES ( ?, ?, ?, ?, ?, ?, ?, ? );] Here are @values: [null '1270950742' '1270951642' 'asdf' 'asdf' 'adsf' 15 ''] Here's the schema of 'timesheet' timesheet( idx INTEGER PRIMARY KEY AUTOINCREMENT, Start_Time VARCHAR, End_Time VARCHAR, Duration INTEGER, Project VARCHAR, Ticket_Number VARCHAR, Site VARCHAR, Notes VARCHAR) Here's how things line up: ---- Insert Statement Schema @values ---- idx idx INTEGER PRIMARY KEY AUTOINCREMENT null: # this is not a mismatch, passing null will allow auto-increment. Start_Time Start_Time VARCHAR '1270950742' End_Time End_Time VARCHAR '1270951642' Project Project VARCHAR 'asdf' Ticket_Number Ticket_Number VARCHAR 'asdf' Site Site VARCHAR 'adsf' Duration Duration INTEGER 15 Notes Notes VARCHAR '' ... I can't see the data-type mis-match.

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• Problem while executing test case in VS2008 test project

  - by sukumar

  Hi all I have the situation as follows I have develpoed one test project in visual studio 2008 to test my target project. I was getting the following exception when i ran test case in my PC System.IO.FileNotFoundException: The specified module could not be found. (Exception from HRESULT: 0x8007007E) at System.Reflection.Assembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection) at System.Reflection.Assembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection) at System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) at System.Reflection.Assembly.InternalLoadFrom(String assemblyFile, Evidence securityEvidence, Byte[] hashValue, AssemblyHashAlgorithm hashAlgorithm, Boolean forIntrospection, StackCrawlMark& stackMark) at System.Reflection.Assembly.LoadFrom(String assemblyFile) at Microsoft.VisualStudio.TestTools.TestTypes.Unit.UnitTestExecuter.GetType(UnitTestElement unitTest, String type) at Microsoft.VisualStudio.TestTools.TestTypes.Unit.UnitTestExecuter.ResolveMethods(). but the same project runs successfully in my colleague PC. as per my Understanding System.IO.FileNotFoundException will occur in case of missing out the dlls. i checked up with dependency walker to trace out the missed dll.dependency walke traced out the following dlls 1)MFC90D.dll 2)mSvcr90d.dll 3)msvcp90d.dll i copied this dlls to C:\windows\system32 from Microsoft visual studio 9.0 dir and again i ran the dependency walker.this time dependency walker is able to open the given testproject dll with 0 errors .even then the same exception comes up when i ran the test. i got fed up with this. can any one tell why it is behaving as PC dependent.is there any thing that i still missing? any suggestion can be helpfull Thakns in Advance Sukumar i

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• Reading DATA from an OBJECT asp.net MVC C#

  - by kalyan

  Hi, I am new to the MVC and I am stuck with a wierd situation. I have to read the Data from the type object and I tried different ways and I couldn't get a solution.Please help. IList<User> u = new UserRepository().Getuser(Name.ToUpper(), UserName.ToUpper(), UserCertNumber.ToUpper(), Date.ToUpper(), UserType.ToUpper(), Company.ToUpper(), PageNumber, Orderby, SearchALL.ToUpper(), PrintAllPages.ToUpper()); object[] users = new object[u.Count]; for (int i = 0; i < u.Count; i++) { users[i] = new { Id = u[i].UserId, Title = u[i].Title, FirstName = u[i].FirstName, LastName = u[i].LastName, Privileges = (from apps in u[i].UserPrivileges select new { PrivilegeId = apps.Privilege.PrivilegeId, PrivilegeName = apps.Privilege.Name, DeactiveDate = apps.DeactiveDate }), Status = (from status in u[i].UserStatus select new { StatusId = status.Status.StatusId, StatusName = status.Status.StatusName, DeactiveDate = status.DeactiveDate }), ActiveDate = u[i].ActiveDate, UserName = u[i].Email, UserCN = (from cert in u[i].UserCertificates select new { CertificateNumber = cert.CertificateNumber, DeactiveDate = cert.DeactiveDate }), Company = u[i].Company.Name }; } string x = ""; string y = ""; var report = users; foreach (var r in report) { x = r[0].....; i want to assign the values from the report to something else and I am not able to read the data from the report object. Please help. } Thank you.

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• Compile time float packing/punning

  - by detly

  I'm writing C for the PIC32MX, compiled with Microchip's PIC32 C compiler (based on GCC 3.4). My problem is this: I have some reprogrammable numeric data that is stored either on EEPROM or in the program flash of the chip. This means that when I want to store a float, I have to do some type punning: typedef union { int intval; float floatval; } IntFloat; unsigned int float_as_int(float fval) { IntFloat intf; intf.floatval = fval; return intf.intval; } // Stores an int of data in whatever storage we're using void StoreInt(unsigned int data, unsigned int address); void StoreFPVal(float data, unsigned int address) { StoreInt(float_as_int(data), address); } I also include default values as an array of compile time constants. For (unsigned) integer values this is trivial, I just use the integer literal. For floats, though, I have to use this Python snippet to convert them to their word representation to include them in the array: import struct hex(struct.unpack("I", struct.pack("f", float_value))[0]) ...and so my array of defaults has these indecipherable values like: const unsigned int DEFAULTS[] = { 0x00000001, // Some default integer value, 1 0x3C83126F, // Some default float value, 0.005 } (These actually take the form of X macro constructs, but that doesn't make a difference here.) Commenting is nice, but is there a better way? It's be great to be able to do something like: const unsigned int DEFAULTS[] = { 0x00000001, // Some default integer value, 1 COMPILE_TIME_CONVERT(0.005), // Some default float value, 0.005 } ...but I'm completely at a loss, and I don't even know if such a thing is possible. Notes Obviously "no, it isn't possible" is an acceptable answer if true. I'm not overly concerned about portability, so implementation defined behaviour is fine, undefined behaviour is not (I have the IDB appendix sitting in front of me). As fas as I'm aware, this needs to be a compile time conversion, since DEFAULTS is in the global scope. Please correct me if I'm wrong about this.

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• Handles Comparison: empty classes vs. undefined classes vs. void*

  - by Nawaz

  Microsoft's GDI+ defines many empty classes to be treated as handles internally. For example, (source GdiPlusGpStubs.h) //Approach 1 class GpGraphics {}; class GpBrush {}; class GpTexture : public GpBrush {}; class GpSolidFill : public GpBrush {}; class GpLineGradient : public GpBrush {}; class GpPathGradient : public GpBrush {}; class GpHatch : public GpBrush {}; class GpPen {}; class GpCustomLineCap {}; There are other two ways to define handles. They're, //Approach 2 class BOOK; //no need to define it! typedef BOOK *PBOOK; typedef PBOOK HBOOK; //handle to be used internally //Approach 3 typedef void* PVOID; typedef PVOID HBOOK; //handle to be used internally I just want to know the advantages and disadvantages of each of these approaches. One advantage with Microsoft's approach is that, they can define type-safe hierarchy of handles using empty classes, which (I think) is not possible with the other two approaches. What else? EDIT: One advantage with the second approach (i.e using incomplete classes) is that we can prevent clients from dereferencing the handles (that means, this approach appears to support encapsulation strongly, I suppose). The code would not even compile if one attempts to dereference handles. What else?

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• inline images in email using javamail

  - by manu1001

  I want to send an email with an inline image using javamail. I'm doing something like this. MimeMultipart content = new MimeMultipart("related"); BodyPart bodyPart = new MimeBodyPart(); bodyPart.setContent(message, "text/html; charset=ISO-8859-1"); content.addBodyPart(bodyPart); bodyPart = new MimeBodyPart(); DataSource ds = new ByteArrayDataSource(image, "image/jpeg"); bodyPart.setDataHandler(new DataHandler(ds)); bodyPart.setHeader("Content-Type", "image/jpeg; name=image.jpg"); bodyPart.setHeader("Content-ID", "<image>"); bodyPart.setHeader("Content-Disposition", "inline"); content.addBodyPart(bodyPart); msg.setContent(content); I've also tried bodyPart.setHeader("inline; filename=image.jpg"); and bodyPart.setDisposition("inline"); but no matter what, the image is being sent as an attachment and the Content-Dispostion is turning into "attachment". How do I send an image inline in the email using javamail?

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• Overriding content_type for Rails Paperclip plugin

  - by Fotios

  I think I have a bit of a chicken and egg problem. I would like to set the content_type of a file uploaded via Paperclip. The problem is that the default content_type is only based on extension, but I'd like to base it on another module. I seem to be able to set the content_type with the before_post_process class Upload < ActiveRecord::Base has_attached_file :upload before_post_process :foo def foo logger.debug "Changing content_type" #This works self.upload.instance_write(:content_type,"foobar") # This fails because the file does not actually exist yet self.upload.instance_write(:content_type,file_type(self.upload.path) end # Returns the filetype based on file command (assume it works) def file_type(path) return `file -ib '#{path}'`.split(/;/)[0] end end But...I cannot base the content type on the file because Paperclip doesn't write the file until after_create. And I cannot seem to set the content_type after it has been saved or with the after_create callback (even back in the controller) So I would like to know if I can somehow get access to the actual file object (assume there are no processors doing anything to the original file) before it is saved, so that I can run the file_type command on that. Or is there a way to modify the content_type after the objects have been created.

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• How to unit test generic classes

  - by Rowland Shaw

  I'm trying to set up some unit tests for an existing compact framework class library. However, I've fallen at the first hurdle, where it appears that the test framework is unable to load the types involved (even though they're both in the class library being tested) Test method MyLibrary.Tests.MyGenericClassTest.MyMethodTest threw exception: System.MissingMethodException: Could not load type 'MyLibrary.MyType' from assembly 'MyLibrary, Version=1.0.3778.36113, Culture=neutral, PublicKeyToken=null'.. My code is loosely: public class MyGenericClass<T> : List<T> where T : MyType, new() { public bool MyMethod(T foo) { throw new NotImplementedException(); } } With test methods: public void MyMethodTestHelper<T>() where T : MyType, new() { MyGenericClass<T> target = new MyGenericClass<T>(); foo = new T(); expected = true; actual = target.MyMethod(foo); Assert.AreEqual(expected, actual); } [TestMethod()] public void MyMethodTest() { MyMethodTestHelper<MyType>(); } I'm a bit stumped though, as I can't even get it to break in the debugger to get to the inner exception, so what else do I check? EDIT this does seem to be something specific to the Compact Framework - recompiling the class libraries and the unit tests for the full framework, gives the expected output (i.e. the debugger stops when I'm going to throw a NotImplementedException).

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• How do you perform arithmetic calculations on symbols in Scheme/Lisp?

  - by kunjaan

  I need to perform calculations with a symbol. I need to convert the time which is of hh:mm form to the minutes passed. ;; (get-minutes symbol)->number ;; convert the time in hh:mm to minutes ;; (get-minutes 6:19)-> 6* 60 + 19 (define (get-minutes time) (let* ((a-time (string->list (symbol->string time))) (hour (first a-time)) (minutes (third a-time))) (+ (* hour 60) minutes))) This is an incorrect code, I get a character after all that conversion and cannot perform a correct calculation. Do you guys have any suggestions? I cant change the input type. Context: The input is a flight schedule so I cannot alter the data structure. ;; ---------------------------------------------------------------------- Edit: Figured out an ugly solution. Please suggest something better. (define (get-minutes time) (let* ((a-time (symbol->string time)) (hour (string->number (substring a-time 0 1))) (minutes (string->number (substring a-time 2 4)))) (+ (* hour 60) minutes)))

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• Conversion between different template instantiation of the same template

  - by Naveen

  I am trying to write an operator which converts between the differnt types of the same implementation. This is the sample code: template <class T = int> class A { public: A() : m_a(0){} template <class U> operator A<U>() { A<U> u; u.m_a = m_a; return u; } private: int m_a; }; int main(void) { A<int> a; A<double> b = a; return 0; } However, it gives the following error for line u.m_a = m_a;. Error 2 error C2248: 'A::m_a' : cannot access private member declared in class 'A' d:\VC++\Vs8Console\Vs8Console\Vs8Console.cpp 30 Vs8Console I understand the error is because A<U> is a totally different type from A<T>. Is there any simple way of solving this (may be using a friend?) other than providing setter and getter methods? I am using Visual studio 2008 if it matters.

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• Aliasing `T*` with `char*` is allowed. Is it also allowed the other way around?

  - by StackedCrooked

  Note: This question has been renamed and reduced to make it more focused and readable. Most of the comments refer to the old text. According to the standard objects of different type may not share the same memory location. So this would not be legal: int i = 0; short * s = reinterpret_cast<short*>(&i); // BAD! The standard however allows an exception to this rule: any object may be accessed through a pointer to char or unsigned char: int i = 0; char * c = reinterpret_cast<char*>(&i); // OK However, it is not clear to me if this is also allowed the other way around. For example: char * c = read_socket(...); unsigned * u = reinterpret_cast<unsigned*>(c); // huh? Summary of the answers The answer is NO for two reasons: You an only access an existing object as char*. There is no object in my sample code, only a byte buffer. The pointer address may not have the right alignment for the target object. In that case dereferencing it would result in undefined behavior. On the Intel and AMD platforms it will result performance overhead. On ARM it will trigger a CPU trap and your program will be terminated! This is a simplified explanation. For more detailed information see answers by @Luc Danton, @Cheers and hth. - Alf and @David Rodríguez.

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• Can not print after upgrading from 12.x to 14.04

  - by user318889

  After upgrading from V12.04 to V14.04 I am not able to print. I am using an HP LaserJet 400 M451dn. The printer troubleshooter told me that there is no solution to the problem. This is the output of the advanced diagnositc output. (Due to limited space I cut the output!) Can anybody tell me what is going wrong. I am using the printer via USB ? Page 1 (Scheduler not running?): {'cups_connection_failure': False} Page 2 (Is local server publishing?): {'local_server_exporting_printers': False} Page 3 (Choose printer): {'cups_dest': , 'cups_instance': None, 'cups_queue': u'HP-LaserJet-400-color-M451dn', 'cups_queue_listed': True} Page 4 (Check printer sanity): {'cups_device_uri_scheme': u'hp', 'cups_printer_dict': {'device-uri': u'hp:/usb/HP_LaserJet_400_color_M451dn?serial=CNFF308670', 'printer-info': u'Hewlett-Packard HP LaserJet 400 color M451dn', 'printer-is-shared': True, 'printer-location': u'Pinatubo', 'printer-make-and-model': u'HP LJ 300-400 color M351-M451 Postscript (recommended)', 'printer-state': 4, 'printer-state-message': u'', 'printer-state-reasons': [u'none'], 'printer-type': 8556636, 'printer-uri-supported': u'ipp://localhost:631/printers/HP-LaserJet-400-color-M451dn'}, 'cups_printer_remote': False, 'hplip_output': (['', '\x1b[01mHP Linux Imaging and Printing System (ver. 3.14.6)\x1b[0m', '\x1b[01mDevice Information Utility ver. 5.2\x1b[0m', '', 'Copyright (c) 2001-13 Hewlett-Packard Development Company, LP', 'This software comes with ABSOLUTELY NO WARRANTY.', 'This is free software, and you are welcome to distribute it', 'under certain conditions. See COPYING file for more details.', '', '', '\x1b[01mhp:/usb/HP_LaserJet_400_color_M451dn?serial=CNFF308670\x1b[0m', '', '\x1b[01mDevice Parameters (dynamic data):\x1b[0m', '\x1b[01m Parameter Value(s) \x1b[0m', ' ---------------------------- ----------------------------------------------------------', ' back-end hp ', " cups-printers ['HP-LaserJet-400-color-M451dn'] ", ' cups-uri hp:/usb/HP_LaserJet_400_color_M451dn?serial=CNFF308670 ', ' dev-file ', ' device-state -1 ', ' device-uri hp:/usb/HP_LaserJet_400_color_M451dn?serial=CNFF308670 ', ' deviceid ', ' error-state 101 ', ' host ', ' is-hp True ', ' panel 0 ', ' panel-line1 ', ' panel-line2 ', ' port 1 ', ' serial CNFF308670 ', ' status-code 5002 ', ' status-desc ', '\x1b[01m', 'Model Parameters (static data):\x1b[0m', '\x1b[01m Parameter Value(s) \x1b[0m', ' ---------------------------- ----------------------------------------------------------', ' align-type 0 ', ' clean-type 0 ', ' color-cal-type 0 ', ' copy-type 0 ', ' embedded-server-type 0 ', ' fax-type 0 ', ' fw-download False ', ' icon hp_color_laserjet_cp2025.png ', ' io-mfp-mode 1 ', ' io-mode 1 ', ' io-support 6 ', ' job-storage 0 ', ' linefeed-cal-type 0 ', ' model HP_LaserJet_400_color_M451dn ', ' model-ui HP LaserJet 400 Color m451dn ', ' model1 HP LaserJet 400 Color M451dn ', ' monitor-type 0 ', ' panel-check-type 0 ', ' pcard-type 0 ', ' plugin 0 ', ' plugin-reason 0 ', ' power-settings 0 ', ' ppd-name lj_300_400_color_m351_m451 ', ' pq-diag-type 0 ', ' r-type 0 ', ' r0-agent1-kind 4 ', ' r0-agent1-sku CE410A/CE410X ', ' r0-agent1-type 1 ', ' r0-agent2-kind 4 ', ' r0-agent2-sku CE411A ', ' r0-agent2-type 4 ', ' r0-agent3-kind 4 ', ' r0-agent3-sku CE413A ', ' r0-agent3-type 5 ', ' r0-agent4-kind 4 ', ' r0-agent4-sku CE412A ', ' r0-agent4-type 6 ', ' scan-src 0 ', ' scan-type 0 ', ' status-battery-check 0 ', ' status-dynamic-counters 0 ', ' status-type 3 ', ' support-released True ', ' support-subtype 2202411 ', ' support-type 2 ', ' support-ver 3.12.2 ', " tech-class ['Postscript'] ", " tech-subclass ['Normal'] ", ' tech-type 4 ', ' usb-pid 3882 ', ' usb-vid 1008 ', ' wifi-config 0 ', '\x1b[01m', 'Status History (most recent first):\x1b[0m', '\x1b[01m Date/Time Code Status Description User Job ID \x1b[0m', ' -------------------- ----- ---------------------------------------- -------- --------', ' 08/21/14 00:07:25 5012 Device communication error richard 0 ', ' 08/20/14 13:42:44 500 Started a print job richard 4214 ', '', '', 'Done.', ''], ['\x1b[35;01mwarning: No display found.\x1b[0m', '\x1b[31;01merror: hp-info -u/--gui requires Qt4 GUI support. Entering interactive mode.\x1b[0m', '\x1b[31;01merror: Unable to communicate with device (code=12): hp:/usb/HP_LaserJet_400_color_M451dn?serial=CNFF308670\x1b[0m', '\x1b[31;01merror: Error opening device (Device not found).\x1b[0m', ''], 0), 'is_cups_class': False, 'local_cups_queue_attributes': {'charset-configured': u'utf-8', 'charset-supported': [u'us-ascii', u'utf-8'], 'color-supported': True, 'compression-supported': [u'none', u'gzip'], 'copies-default': 1, 'copies-supported': (1, 9999), 'cups-version': u'1.7.2', 'device-uri': u'hp:/usb/HP_LaserJet_400_color_M451dn?serial=CNFF308670', 'document-format-default': u'application/octet-stream', 'document-format-supported': [u'application/octet-stream', u'application/pdf', u'application/postscript', u'application/vnd.adobe-reader-postscript', u'application/vnd.cups-command', u'application/vnd.cups-pdf', u'application/vnd.cups-pdf-banner', u'application/vnd.cups-postscript', u'application/vnd.cups-raw', u'application/vnd.samsung-ps', u'application/x-cshell', u'application/x-csource', u'application/x-perl', u'application/x-shell', u'image/gif', u'image/jpeg', u'image/png', u'image/tiff', u'image/urf', u'image/x-bitmap', u'image/x-photocd', u'image/x-portable-anymap', u'image/x-portable-bitmap', u'image/x-portable-graymap', u'image/x-portable-pixmap', u'image/x-sgi-rgb', u'image/x-sun-raster', u'image/x-xbitmap', u'image/x-xpixmap', u'image/x-xwindowdump', u'text/css', u'text/html', u'text/plain'], 'finishings-default': 3, 'finishings-supported': [3], 'generated-natural-language-supported': [u'en-us'], 'ipp-versions-supported': [u'1.0', u'1.1', u'2.0', u'2.1'], 'ippget-event-life': 15, 'job-creation-attributes-supported': [u'copies', u'finishings', u'ipp-attribute-fidelity', u'job-hold-until', u'job-name', u'job-priority', u'job-sheets', u'media', u'media-col', u'multiple-document-handling', u'number-up', u'output-bin', u'orientation-requested', u'page-ranges', u'print-color-mode', u'print-quality', u'printer-resolution', u'sides'], 'job-hold-until-default': u'no-hold', 'job-hold-until-supported': [u'no-hold', u'indefinite', u'day-time', u'evening', u'night', u'second-shift', u'third-shift', u'weekend'], 'job-ids-supported': True, 'job-k-limit': 0, 'job-k-octets-supported': (0, 470914416), 'job-page-limit': 0, 'job-priority-default': 50, 'job-priority-supported': [100], 'job-quota-period': 0, 'job-settable-attributes-supported': [u'copies', u'finishings', u'job-hold-until', u'job-name', u'job-priority', u'media', u'media-col', u'multiple-document-handling', u'number-up', u'output-bin', u'orientation-requested', u'page-ranges', u'print-color-mode', u'print-quality', u'printer-resolution', u'sides'], 'job-sheets-default': (u'none', u'none'), 'job-sheets-supported': [u'none', u'classified', u'confidential', u'form', u'secret', u'standard', u'topsecret', u'unclassified'], 'jpeg-k-octets-supported': (0, 470914416), 'jpeg-x-dimension-supported': (0, 65535), 'jpeg-y-dimension-supported': (1, 65535), 'marker-change-time': 0, 'media-bottom-margin-supported': [423], 'media-col-default': u'(unknown IPP value tag 0x34)', 'media-col-supported': [u'media-bottom-margin', u'media-left-margin', u'media-right-margin', u'media-size', u'media-source', u'media-top-margin', u'media-type'], 'media-default': u'iso_a4_210x297mm', 'media-left-margin-supported': [423], 'media-right-margin-supported': [423],

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• Having a generic data type for a database table column, is it "good" practice?

  - by Yanick Rochon

  I'm working on a PHP project where some object (class member) may contain different data type. For example : class Property { private $_id; // (PK) private $_ref_id; // the object reference id (FK) private $_name; // the name of the property private $_type; // 'string', 'int', 'float(n,m)', 'datetime', etc. private $_data; // ... // ..snip.. public getters/setters } Now, I need to perform some persistence on these objects. Some properties may be a text data type, but nothing bigger than what a varchar may hold. Also, later on, I need to be able to perform searches and sorting. Is it a good practice to use a single database table for this (ie. is there a non negligible performance impact)? If it's "acceptable", then what could be the data type for the data column?

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• I have a new file type that I would like to handle in gnome how to get file properties?

  - by Mark

  I have a new file type that I would like to handle in gnome. Establishing a new mime type, a new thumbnailer and a new application to display the file type is done. But I need a new tab on the file properties page. This tab is analogous to the tabs for exif information for jpg files or for encoding information for video codecs, that says how long the video is. The files concerned are embroidery files and the file properties needed to be displayed are things like phisical dimentions of the design, how much thread will be used and how many colours. My belief is that with current gnome 3 this is not possible, am I right? Or should I take a wider view that in Ubuntu, anything is possible, just may be a bit difficult?

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• Doing TDD Silverlight 4 RC using Visual Studio 2010 RC

  - by user133992

  First I am glad to see better TDD support in VS2010. Support for generating code stubs from my tests is ok - not as good as more mature TDD plug-ins but a good start. I am looking for some best Silverlight 4.0 TDD practices. First Question: Anyone have links, recommendations? I know the new Silverlight Unit Test capabilities are much better (Jeff Wilcox's Mix Presentation). What I am focusing on right now is using TDD to develop pure Silverlight 4.0 Class Library projects - projects without a Silverlight UI project. I've been able to get it to work but not as cleanly as it should be. I can create an Empty VS project. Add A Silverlight 4 Class Library Project. Add a TestProject (not a silverlight Unit Test Project but a plain Test Project). Add a simple test in the Test Project such as: namespace Calculator.Test { [TestClass] public class CalculatorTests { [TestMethod] public void CalulatorAddTest() { Calc c = new Calc(); int expected = 10; int actual = c.Add(6, 4); Assert.AreEqual<int>(expected, actual); } } } Using the new Generate Type and Method from Test feature it will generate the following code in the Silverlight Project: namespace Calculator { public class Calc { public int Add(int p, int p_2) { throw new NotImplementedException(); } } } When I run the tests the first time it says the target assembly is Silverlight and not able to run test - Not exact text but the same general idea. When I change the implementation to: namespace Calculator { public class Calc { public int Add(int p, int p_2) { return p + p_2; } } } and re-run the test, it works fine and the test goes green. It also works for all other TDD code I generate after. I also get a warning Mark in the Test Project's reference to the Calculator Silverlight Class Library Assembly. Second Question: Any comments ideas if this just a bug in VS2010 RC or is Silverlight Class Library TDD not really supported. I have not created a Silverlight UI project or changed and build or debug settings so I have no idea what is hosting the silverlight DLL. Finally, some of the Silverlight Class Libraries I need to write will provide functionality that requires elevated Out-Of-Browser rights. Based on the above, it looks like I can use TDD Test Projects against regular Silverlight 4.0 Class Libraries, but I have no idea how I can TDD the elevated OOB functionality without also creating the UI component that gets installed. The UI piece is not really needed for the Library development and gets in the way of what I actually want to TDD. I know I can (and will) mock some of that functionality but at some point I will also need the real thing in my tests. Third Question: Any ideas how to TDD Silverlight 4.0 Class Library project that requires OOB elevated rights? Thanks!

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• C# Reading and Writing a Char[] to and from a Byte[]

  - by Simon G

  Hi, I have a byte array of around 10,000 bytes which is basically a blob from delphi that contains char, string, double and arrays of various types. This need to be read in and updated via C#. I've created a very basic reader that gets the byte array from the db and converts the bytes to the relevant object type when accessing the property which works fine. My problem is when I try to write to a specific char[] item, it doesn't seem to update the byte array. I've created the following extensions for reading and writing: public static class CharExtension { public static byte ToByte( this char c ) { return Convert.ToByte( c ); } public static byte ToByte( this char c, int position, byte[] blob ) { byte b = c.ToByte(); blob[position] = b; return b; } } public static class CharArrayExtension { public static byte[] ToByteArray( this char[] c ) { byte[] b = new byte[c.Length]; for ( int i = 1; i < c.Length; i++ ) { b[i] = c[i].ToByte(); } return b; } public static byte[] ToByteArray( this char[] c, int positon, int length, byte[] blob ) { byte[] b = c.ToByteArray(); Array.Copy( b, 0, blob, positon, length ); return b; } } public static class ByteExtension { public static char ToChar( this byte[] b, int position ) { return Convert.ToChar( b[position] ); } } public static class ByteArrayExtension { public static char[] ToCharArray( this byte[] b, int position, int length ) { char[] c = new char[length]; for ( int i = 0; i < length; i++ ) { c[i] = b.ToChar( position ); position += 1; } return c; } } to read and write chars and char arrays my code looks like: Byte[] _Blob; // set from a db field public char ubin { get { return _tariffBlob.ToChar( 14 ); } set { value.ToByte( 14, _Blob ); } } public char[] usercaplas { get { return _tariffBlob.ToCharArray( 2035, 10 ); } set { value.ToByteArray( 2035, 10, _Blob ); } } So to write to the objects I can do: ubin = 'C'; // this will update the byte[] usercaplas = new char[10] { 'A', 'B', etc. }; // this will update the byte[] usercaplas[3] = 'C'; // this does not update the byte[] I know the reason is that the setter property is not being called but I want to know is there a way around this using code similar to what I already have? I know a possible solution is to use a private variable called _usercaplas that I set and update as needed however as the byte array is nearly 10,000 bytes in length the class is already long and I would like a simpler approach as to reduce the overall code length and complexity. Thank

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• A standard event messaging system with AJAX?

  - by Gutzofter

  Is there any standards or messaging framework for AJAX? Right now I have a single page that loads content using Ajax. Because I had a complex form for data entry as part of my content, I need to validate certain events that can occur in my form. So after some adjustments driven by my tests: asyncShould("search customer list click", 3, function() { stop(1000); $('#content').show(); var forCustomerList = newCustomerListRequest(); var forShipAndCharge = newShipAndChargeRequest(forCustomerList); forCustomerList.page = '../../vt/' + forCustomerList.page; forShipAndCharge.page = 'helpers/helper.php'; forShipAndCharge.data = { 'action': 'shipAndCharge', 'DB': '11001' }; var originalComplete = forShipAndCharge.complete; forShipAndCharge.complete = function(xhr, status) { originalComplete(xhr, status); ok($('#customer_edit').is(":visible"), 'Shows customer editor'); $('#search').click(); ok($('#customer_list').is(":visible"), 'Shows customer list'); ok($('#customer_edit').is(":hidden"), 'Does not show customer editor'); start(); }; testController.getContent(forShipAndCharge); }); Here is the controller for getting content: getContent: function (request) { $.ajax({ type: 'GET', url: request.page, dataType: 'json', data: request.data, async: request.async, success: request.success, complete: request.complete }); }, And here is the request event: function newShipAndChargeRequest(serverRequest) { var that = { serverRequest: serverRequest, page: 'nodes/orders/sc.php', data: 'customer_id=-1', complete: errorHandler, success: function(msg) { shipAndChargeHandler(msg); initWhenCustomer(that.serverRequest); }, async: true }; return that; } And here is a success handler: function shipAndChargeHandler(msg) { $('.contentContainer').html(msg.html); if (msg.status == 'flash') { flash(msg.flash); } } And on my server side I end up with a JSON structure that looks like this: $message['status'] = 'success'; $message['data'] = array(); $message['flash'] = ''; $message['html'] = ''; echo json_encode($message); So now loading content consists of two parts: HTML, this is the presentation of the form. DATA, this is any data that needs be loaded for the form FLASH, any validation or server errors STATUS tells client what happened on server. My question is: Is this a valid way to handle event messaging on the client-side or am I going down a path of heartache and pain?

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• Visual Studio 2010 and Test Driven Development

  - by devoured elysium

  I'm making my first steps in Test Driven Development with Visual Studio. I have some questions regarding how to implement generic classes with VS 2010. First, let's say I want to implement my own version of an ArrayList. I start by creating the following test (I'm using in this case MSTest): [TestMethod] public void Add_10_Items_Remove_10_Items_Check_Size_Is_Zero() { var myArrayList = new MyArrayList<int>(); for (int i = 0; i < 10; ++i) { myArrayList.Add(i); } for (int i = 0; i < 10; ++i) { myArrayList.RemoveAt(0); } int expected = 0; int actual = myArrayList.Size; Assert.AreEqual(expected, actual); } I'm using VS 2010 ability to hit ctrl + . and have it implement classes/methods on the go. I have been getting some trouble when implementing generic classes. For example, when I define an .Add(10) method, VS doesn't know if I intend a generic method(as the class is generic) or an Add(int number) method. Is there any way to differentiate this? The same can happen with return types. Let's assume I'm implementing a MyStack stack and I want to test if after I push and element and pop it, the stack is still empty. We all know pop should return something, but usually, the code of this test shouldn't care for it. Visual Studio would then think that pop is a void method, which in fact is not what one would want. How to deal with this? For each method, should I start by making tests that are "very specific" such as is obvious the method should return something so I don't get this kind of ambiguity? Even if not using the result, should I have something like int popValue = myStack.Pop() ? How should I do tests to generic classes? Only test with one generic kind of type? I have been using ints, as they are easy to use, but should I also test with different kinds of objects? How do you usually approach this? I see there is a popular tool called TestDriven for .NET. With VS 2010 release, is it still useful, or a lot of its features are now part of VS 2010, rendering it kinda useless? Thanks

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• Any suggestions for improvement on this style for BDD/TDD?

  - by Sean B

  I was tinkering with doing the setups with our unit test specifciations which go like Specification for SUT when behaviour X happens in scenario Y Given that this thing And also this other thing When I do X... Then It should do ... And It should also do ... I wrapped each of the steps of the GivenThat in Actions... any feed back whether separating with Actions is good / bad / or better way to make the GivenThat clear? /// <summary> /// Given a product is setup for injection /// And Product Image Factory Is Stubbed(); /// And Product Size Is Stubbed(); /// And Drawing Scale Is Stubbed(); /// And Product Type Is Stubbed(); /// </summary> protected override void GivenThat() { base.GivenThat(); Action givenThatAProductIsSetupforInjection = () => { var randomGenerator = new RandomGenerator(); this.Position = randomGenerator.Generate<Point>(); this.Product = new Diffuser { Size = new RectangularProductSize( 2.Inches()), Position = this.Position, ProductType = Dep<IProductType>() }; }; Action andProductImageFactoryIsStubbed = () => Dep<IProductBitmapImageFactory>().Stub(f => f.GetInstance(Dep<IProductType>())).Return(ExpectedBitmapImage); Action andProductSizeIsStubbed = () => { Stub<IDisplacementProduct, IProductSize>(p => p.Size); var productBounds = new ProductBounds(Width.Feet(), Height.Feet()); Dep<IProductSize>().Stub(s => s.Bounds).Return(productBounds); }; Action andDrawingScaleIsStubbed = () => Dep<IDrawingScale>().Stub(s => s.PixelsPerFoot).Return(PixelsPerFoot); Action andProductTypeIsStubbed = () => Stub<IDisplacementProduct, IProductType>(p => p.ProductType); givenThatAProductIsSetupforInjection(); andProductImageFactoryIsStubbed(); andProductSizeIsStubbed(); andDrawingScaleIsStubbed(); andProductTypeIsStubbed(); }

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• Returning different data types C#

  - by user1810659

  i have create a class library (DLL) with many different methods. and the return different types of data(string string[] double double[]). Therefore i have created one class i called CustomDataType for all the methods containing different data types so each method in the Library can return object of the custom class and this way be able to return multiple data types I have done it like this: public class CustomDataType { public double Value; public string Timestamp; public string Description; public string Unit; // special for GetparamterInfo public string OpcItemUrl; public string Source; public double Gain; public double Offset; public string ParameterName; public int ParameterID; public double[] arrayOfValue; public string[] arrayOfTimestamp; // public string[] arrayOfParameterName; public string[] arrayOfUnit; public string[] arrayOfDescription; public int[] arrayOfParameterID; public string[] arrayOfItemUrl; public string[] arrayOfSource; public string[] arrayOfModBusRegister; public string[] arrayOfGain; public string[] arrayOfOffset; } The Library contains methods like these: public CustomDataType GetDeviceParameters(string deviceName) { ...................... code getDeviceParametersObj.arrayOfParameterName; return getDeviceParametersObj; } public CustomDataType GetMaxMin(string parameterName, string period, string maxMin) { .....................................code getMaxMingObj.Value = (double)reader["MaxMinValue"]; getMaxMingObj.Timestamp = reader["MeasurementDateTime"].ToString(); getMaxMingObj.Unit = reader["Unit"].ToString(); getMaxMingObj.Description = reader["Description"].ToString(); return getMaxMingObj; } public CustomDataType GetSelectedMaxMinData(string[] parameterName, string period, string mode) {................................code selectedMaxMinObj.arrayOfValue = MaxMinvalueList.ToArray(); selectedMaxMinObj.arrayOfTimestamp = MaxMintimeStampList.ToArray(); selectedMaxMinObj.arrayOfDescription = MaxMindescriptionList.ToArray(); selectedMaxMinObj.arrayOfUnit = MaxMinunitList.ToArray(); return selectedMaxMinObj; } As illustrated thi different methods returns different data types,and it works fine for me but when i import the DLL and want to use the methods Visual studio shwos all the data types in the CustomDataType class as suggestion for all the methods even though the return different data.This is illusrtated in the picture below. As we can see from the picture with the suggestion of all the different return data the user can get confused and choose wrong return data for some of the methods. So my question is how can i improve this. so Visual studio suggest just the belonging return data type for each method.

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• String.valueOf(int value) gives error [closed]

  - by Davidrd91

  I am trying to convert an int into a String so that I can put the String values into an SQLite Cursor. I've tried multiple syntax and methods but none seem to work for me. The Error occurs in MangaItemDB() while trying to convert any Int types aswell as the boolean. I've looked through several articles like this one but none works for me. Here's my code: public class MangaItem { private int _id; private String mangaName; private String mangaLink; private static String mangaAlpha; private static int mangaCount; private static int alphaCount; private boolean mangaComplete = false; public MangaItem MangaItemDB(int id, String mangaName, String mangaLink, String mangaAlpha, String mangaCount, String alphaCount, String mangaComplete) { MangaItem MangaItemDB = new MangaItem(); MangaItemDB._id = id; MangaItemDB.mangaName = mangaName; MangaItemDB.mangaLink = mangaLink; MangaItemDB.mangaAlpha = mangaAlpha; MangaItemDB.mangaCount = String.valueOf(int mangaCount); MangaItemDB.alphaCount = Integer.toString(getAlphaCount()); MangaItemDB.mangaComplete = String.valueOf(getMangaComplete()); return MangaItemDB; } public void incrementMangaCount() { mangaCount++; } public int getMangaCount() { return mangaCount; } public void incrementAlphaCount() { alphaCount++; } public int getAlphaCount() { return alphaCount; } public boolean setMangaComplete(boolean mangaComplete) { return true; } public boolean getMangaComplete() { return mangaComplete; } /** * @return the mangaName */ public String getMangaName() { return mangaName; } /** * @param mangaName the mangaName to set */ public void setMangaName(String mangaName) { this.mangaName = mangaName; } /** * @return the mangaLink */ public String getMangaLink() { return mangaLink; } /** * @param mangaLink the mangaLink to set */ public void setMangaLink(String mangaLink) { this.mangaLink = mangaLink; } /** * @return the mangaAlpha */ public String getMangaAlpha() { return mangaAlpha; } /** * @param mangaAlpha the mangaAlpha to set */ public void setMangaAlpha(String mangaAlpha) { this.mangaAlpha = mangaAlpha; } /** * @return the _id */ public int get_id() { return _id; } /** * @param _id the _id to set */ public void set_id(int _id) { this._id = _id; } } The lines : MangaItemDB.mangaCount = String.valueOf(mangaCount); MangaItemDB.alphaCount = Integer.toString(getAlphaCount()); MangaItemDB.mangaComplete = String.valueOf(getMangaComplete()); all give "Type mismatch: cannot convert from String to Int"

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• Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 3 – Table per Concrete Type (TPC) and Choosing Strategy Guidelines

  - by mortezam

  This is the third (and last) post in a series that explains different approaches to map an inheritance hierarchy with EF Code First. I've described these strategies in previous posts: Part 1 – Table per Hierarchy (TPH) Part 2 – Table per Type (TPT)In today’s blog post I am going to discuss Table per Concrete Type (TPC) which completes the inheritance mapping strategies supported by EF Code First. At the end of this post I will provide some guidelines to choose an inheritance strategy mainly based on what we've learned in this series. TPC and Entity Framework in the Past Table per Concrete type is somehow the simplest approach suggested, yet using TPC with EF is one of those concepts that has not been covered very well so far and I've seen in some resources that it was even discouraged. The reason for that is just because Entity Data Model Designer in VS2010 doesn't support TPC (even though the EF runtime does). That basically means if you are following EF's Database-First or Model-First approaches then configuring TPC requires manually writing XML in the EDMX file which is not considered to be a fun practice. Well, no more. You'll see that with Code First, creating TPC is perfectly possible with fluent API just like other strategies and you don't need to avoid TPC due to the lack of designer support as you would probably do in other EF approaches. Table per Concrete Type (TPC)In Table per Concrete type (aka Table per Concrete class) we use exactly one table for each (nonabstract) class. All properties of a class, including inherited properties, can be mapped to columns of this table, as shown in the following figure: As you can see, the SQL schema is not aware of the inheritance; effectively, we’ve mapped two unrelated tables to a more expressive class structure. If the base class was concrete, then an additional table would be needed to hold instances of that class. I have to emphasize that there is no relationship between the database tables, except for the fact that they share some similar columns. TPC Implementation in Code First Just like the TPT implementation, we need to specify a separate table for each of the subclasses. We also need to tell Code First that we want all of the inherited properties to be mapped as part of this table. In CTP5, there is a new helper method on EntityMappingConfiguration class called MapInheritedProperties that exactly does this for us. Here is the complete object model as well as the fluent API to create a TPC mapping: public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } }          public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } }          public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } }      public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; }              protected override void OnModelCreating(ModelBuilder modelBuilder)     {         modelBuilder.Entity<BankAccount>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("BankAccounts");         });         modelBuilder.Entity<CreditCard>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("CreditCards");         });                 } } The Importance of EntityMappingConfiguration ClassAs a side note, it worth mentioning that EntityMappingConfiguration class turns out to be a key type for inheritance mapping in Code First. Here is an snapshot of this class: namespace System.Data.Entity.ModelConfiguration.Configuration.Mapping {     public class EntityMappingConfiguration<TEntityType> where TEntityType : class     {         public ValueConditionConfiguration Requires(string discriminator);         public void ToTable(string tableName);         public void MapInheritedProperties();     } } As you have seen so far, we used its Requires method to customize TPH. We also used its ToTable method to create a TPT and now we are using its MapInheritedProperties along with ToTable method to create our TPC mapping. TPC Configuration is Not Done Yet!We are not quite done with our TPC configuration and there is more into this story even though the fluent API we saw perfectly created a TPC mapping for us in the database. To see why, let's start working with our object model. For example, the following code creates two new objects of BankAccount and CreditCard types and tries to add them to the database: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount();     CreditCard creditCard = new CreditCard() { CardType = 1 };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Running this code throws an InvalidOperationException with this message: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges. The reason we got this exception is because DbContext.SaveChanges() internally invokes SaveChanges method of its internal ObjectContext. ObjectContext's SaveChanges method on its turn by default calls AcceptAllChanges after it has performed the database modifications. AcceptAllChanges method merely iterates over all entries in ObjectStateManager and invokes AcceptChanges on each of them. Since the entities are in Added state, AcceptChanges method replaces their temporary EntityKey with a regular EntityKey based on the primary key values (i.e. BillingDetailId) that come back from the database and that's where the problem occurs since both the entities have been assigned the same value for their primary key by the database (i.e. on both BillingDetailId = 1) and the problem is that ObjectStateManager cannot track objects of the same type (i.e. BillingDetail) with the same EntityKey value hence it throws. If you take a closer look at the TPC's SQL schema above, you'll see why the database generated the same values for the primary keys: the BillingDetailId column in both BankAccounts and CreditCards table has been marked as identity. How to Solve The Identity Problem in TPC As you saw, using SQL Server’s int identity columns doesn't work very well together with TPC since there will be duplicate entity keys when inserting in subclasses tables with all having the same identity seed. Therefore, to solve this, either a spread seed (where each table has its own initial seed value) will be needed, or a mechanism other than SQL Server’s int identity should be used. Some other RDBMSes have other mechanisms allowing a sequence (identity) to be shared by multiple tables, and something similar can be achieved with GUID keys in SQL Server. While using GUID keys, or int identity keys with different starting seeds will solve the problem but yet another solution would be to completely switch off identity on the primary key property. As a result, we need to take the responsibility of providing unique keys when inserting records to the database. We will go with this solution since it works regardless of which database engine is used. Switching Off Identity in Code First We can switch off identity simply by placing DatabaseGenerated attribute on the primary key property and pass DatabaseGenerationOption.None to its constructor. DatabaseGenerated attribute is a new data annotation which has been added to System.ComponentModel.DataAnnotations namespace in CTP5: public abstract class BillingDetail {     [DatabaseGenerated(DatabaseGenerationOption.None)]     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } As always, we can achieve the same result by using fluent API, if you prefer that: modelBuilder.Entity<BillingDetail>()             .Property(p => p.BillingDetailId)             .HasDatabaseGenerationOption(DatabaseGenerationOption.None); Working With The Object Model Our TPC mapping is ready and we can try adding new records to the database. But, like I said, now we need to take care of providing unique keys when creating new objects: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount()      {          BillingDetailId = 1                          };     CreditCard creditCard = new CreditCard()      {          BillingDetailId = 2,         CardType = 1     };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Polymorphic Associations with TPC is Problematic The main problem with this approach is that it doesn’t support Polymorphic Associations very well. After all, in the database, associations are represented as foreign key relationships and in TPC, the subclasses are all mapped to different tables so a polymorphic association to their base class (abstract BillingDetail in our example) cannot be represented as a simple foreign key relationship. For example, consider the the domain model we introduced here where User has a polymorphic association with BillingDetail. This would be problematic in our TPC Schema, because if User has a many-to-one relationship with BillingDetail, the Users table would need a single foreign key column, which would have to refer both concrete subclass tables. This isn’t possible with regular foreign key constraints. Schema Evolution with TPC is Complex A further conceptual problem with this mapping strategy is that several different columns, of different tables, share exactly the same semantics. This makes schema evolution more complex. For example, a change to a base class property results in changes to multiple columns. It also makes it much more difficult to implement database integrity constraints that apply to all subclasses. Generated SQLLet's examine SQL output for polymorphic queries in TPC mapping. For example, consider this polymorphic query for all BillingDetails and the resulting SQL statements that being executed in the database: var query = from b in context.BillingDetails select b; Just like the SQL query generated by TPT mapping, the CASE statements that you see in the beginning of the query is merely to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type). TPC's SQL Queries are Union Based As you can see in the above screenshot, the first SELECT uses a FROM-clause subquery (which is selected with a red rectangle) to retrieve all instances of BillingDetails from all concrete class tables. The tables are combined with a UNION operator, and a literal (in this case, 0 and 1) is inserted into the intermediate result; (look at the lines highlighted in yellow.) EF reads this to instantiate the correct class given the data from a particular row. A union requires that the queries that are combined, project over the same columns; hence, EF has to pad and fill up nonexistent columns with NULL. This query will really perform well since here we can let the database optimizer find the best execution plan to combine rows from several tables. There is also no Joins involved so it has a better performance than the SQL queries generated by TPT where a Join is required between the base and subclasses tables. Choosing Strategy GuidelinesBefore we get into this discussion, I want to emphasize that there is no one single "best strategy fits all scenarios" exists. As you saw, each of the approaches have their own advantages and drawbacks. Here are some rules of thumb to identify the best strategy in a particular scenario: If you don’t require polymorphic associations or queries, lean toward TPC—in other words, if you never or rarely query for BillingDetails and you have no class that has an association to BillingDetail base class. I recommend TPC (only) for the top level of your class hierarchy, where polymorphism isn’t usually required, and when modification of the base class in the future is unlikely. If you do require polymorphic associations or queries, and subclasses declare relatively few properties (particularly if the main difference between subclasses is in their behavior), lean toward TPH. Your goal is to minimize the number of nullable columns and to convince yourself (and your DBA) that a denormalized schema won’t create problems in the long run. If you do require polymorphic associations or queries, and subclasses declare many properties (subclasses differ mainly by the data they hold), lean toward TPT. Or, depending on the width and depth of your inheritance hierarchy and the possible cost of joins versus unions, use TPC. By default, choose TPH only for simple problems. For more complex cases (or when you’re overruled by a data modeler insisting on the importance of nullability constraints and normalization), you should consider the TPT strategy. But at that point, ask yourself whether it may not be better to remodel inheritance as delegation in the object model (delegation is a way of making composition as powerful for reuse as inheritance). Complex inheritance is often best avoided for all sorts of reasons unrelated to persistence or ORM. EF acts as a buffer between the domain and relational models, but that doesn’t mean you can ignore persistence concerns when designing your classes. SummaryIn this series, we focused on one of the main structural aspect of the object/relational paradigm mismatch which is inheritance and discussed how EF solve this problem as an ORM solution. We learned about the three well-known inheritance mapping strategies and their implementations in EF Code First. Hopefully it gives you a better insight about the mapping of inheritance hierarchies as well as choosing the best strategy for your particular scenario. Happy New Year and Happy Code-Firsting! References ADO.NET team blog Java Persistence with Hibernate book a { color: #5A99FF; } a:visited { color: #5A99FF; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } .exception { background-color: #f0f0f0; font-style: italic; padding-bottom: 5px; padding-left: 5px; padding-top: 5px; padding-right: 5px; }

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