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  • MVC Entity Framework Model not returning correct data

    - by quagland
    Hi, Run into a strange problem while writing an ASP.NET MVC site. I have a view in my SQL Server database that returns a few date ranges. The view works fine when running the query in SSMS. When the view data is returned by the Entity Framework Model, It returns the correct number of rows but some of the rows are duplicated. Here is an example of what I have done: SQL Server code: CREATE TABLE [dbo].[A]( [ID] [int] NOT NULL, [PhID] [int] NULL, [FromDate] [datetime] NULL, [ToDate] [datetime] NULL, CONSTRAINT [PK_A] PRIMARY KEY CLUSTERED ([ID] ASC)) ON [PRIMARY] go CREATE TABLE [dbo].[B]( [PhID] [int] NOT NULL, [FromDate] [datetime] NULL, [ToDate] [datetime] NULL, CONSTRAINT [PK_B] PRIMARY KEY CLUSTERED ( [PhID] ASC )) ON [PRIMARY] go CREATE VIEW C as SELECT A.ID, CASE WHEN A.PhID IS NULL THEN A.FromDate ELSE B.FromDate END AS FromDate, CASE WHEN A.PhID IS NULL THEN A.ToDate ELSE B.ToDate END AS ToDate FROM A LEFT OUTER JOIN B ON A.PhID = B.PhID go INSERT INTO B (PhID, FromDate, ToDate) VALUES (100, '20100615', '20100715') INSERT INTO A (ID, PhID, FromDate, ToDate) VALUES (1, NULL, '20100101', '20100201') INSERT INTO A (ID, PhID, FromDate, ToDate) VALUES (1, 100, '20100615', '20100715') INSERT INTO B (PhID, FromDate, ToDate) VALUES (101, '20101201', '20101231') INSERT INTO A (ID, PhID, FromDate, ToDate) VALUES (2, NULL, '20100801', '20100901') INSERT INTO A (ID, PhID, FromDate, ToDate) VALUES (2, 101, '20101201', '20101231') So now, if you select all from C, you get 4 separate date ranges In the Entity Framework Model (which I call 'Core'), the view 'C' is added. in MVC Controller: public class HomeController : Controller { public ActionResult Index() { CoreEntities db = new CoreEntities(); var clist = from c in db.C select c; return View(clist.ToList()); } } in MVC View: @model List<RM.Models.C> @{ foreach (RM.Models.C c in Model) { @String.Format("{0:dd-MMM-yyyy}", c.FromDate) <span>-</span> @String.Format("{0:dd-MMM-yyyy}", c.ToDate) <br /> } } When I run all this, it outputs this: 01-Jan-2010 - 01-Feb-2010 01-Jan-2010 - 01-Feb-2010 01-Aug-2010 - 01-Sep-2010 01-Aug-2010 - 01-Sep-2010 When it should do this (this is what the view returns): 01-Jan-2010 - 01-Feb-2010 15-Jun-2010 - 15-Jul-2010 01-Aug-2010 - 01-Sep-2010 01-Dec-2010 - 31-Dec-2010 Also, I've run the SQL profiler over it and according to that, the query being executed is: SELECT [Extent1].[ID] AS [ID], [Extent1].[FromDate] AS [FromDate], [Extent1].[ToDate] AS [ToDate] FROM (SELECT [C].[ID] AS [ID], [C].[FromDate] AS [FromDate], [C].[ToDate] AS [ToDate] FROM [dbo].[C] AS [C]) AS [Extent1] Which returns the correct data So it seems that the entity framework is doing something to the data in the meantime. To me, everything looks fine! Have I missed something? Cheers, Ben

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  • Unobtrusive Maximum Input Lengths with JQuery and FluentValidation

    - by Steve Wilkes
    If you use FluentValidation and set a maximum length for a string or a maximum  value for a numeric property, JQuery validation is used to show an error message when the user inputs too many characters or a numeric value which is too big. On a recent project we wanted to use input’s maxlength attribute to prevent a user from entering too many characters rather than cure the problem with an error message, and I added this JQuery to add maxlength attributes based on JQuery validation’s data- attributes. $(function () { $("input[data-val-range-max],input[data-val-length-max]").each(function (i, e) { var input = $(e); var maxlength = input.is("[data-val-range-max]") ? input.data("valRangeMax").toString().length : input.data("valLengthMax"); input.attr("maxlength", maxlength); }); }); Presto!

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  • get all words using java

    - by hussain
    i want to know how to get all word using java String first[]={"a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"}; String second[]={"a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"}; String ch =""; String total[]; for(int i = 0;i<26;i++) { for(int j = 0;j<26;j++) { ch+=first[i]+first[j]; System.out.println(ch); } } i get only 576 words only by this program but the 26! words is 4.03291461 × 1026 how to write the program in java thanks and advance

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  • Running activity from remote service

    - by Moshik
    Hi, iam trying to run an activity from diffrent package from my remote service: this is how i implement the service.java ublic class CurrencyService extends Service { public class CurrencyServiceImpl extends ICurrencyService.Stub { int CALL_PUSH_SERVICE_ACTIVITY=10; @Override public void callSomeActivity(int activityId) throws RemoteException { Intent pushActivity=new Intent("com.pushservice.PushActivity"); pushActivity.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); startActivity(pushActivity); .. ive also added a line in the manifest of the service: the service works fine, but i cant run the activity - PushActivity which is in diffrent package of diffrent application, thanks.

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  • Core Data - Relationship to dissimilar entities

    - by carotene
    Suppose I have the following data model: Entity Person Attribute name String Attribute personType String Attribute dailyRecords Entity CarpenterDailyRecord Attribute numberOfNailsHammered Int Attribute picNameOfFinishedCabinet String Entity WindowWasherDailyRecord Attribute nameOfBuildingWashed String Attribute numberOfWindowsWashed Int I would like to establish a to-many relationship between the Person.dailyRecords and 1 of the daily record entities (which changes depending on the person type). Of course, i could create a CarpenterPerson and WindowWasher entity which each points to it's unique daily record structure, but i have to group people together in my app somehow. so if i do a Group Entity: Entity Group Attribute people array i'm still stuck. how do i point to multiple & different Person entities? There must be an obvious answer, it's just i'm so new to all of this. thanks!

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  • initializer_list in the VC10

    - by user335870
    hi i wrote this program in VC++ 2010: class class1 { public: class1 (initializer_list<int> a){}; int foo; float Bar; }; void main() { class1 c = {2,3}; getchar(); } but i get this errors when i compile project: Error 1 error C2552: 'c' : non-aggregates cannot be initialized with initializer list c:\users\pswin\documents\visual studio 2010\projects\test_c++0x\test_c++0x\main.cpp 27 and 2 IntelliSense: initialization with '{...}' is not allowed for object of type "class1" c:\users\pswin\documents\visual studio 2010\projects\test_c++0x\test_c++0x\main.cpp 27 what is the problem?

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  • How can i use 'log' inside a src/groovy/ class

    - by firnnauriel
    I'm encountering this error: groovy.lang.MissingPropertyException: No such property: log for class: org.utils.MyClass Here's the content of the class: package org.utils class MyClass { int organizationCount = 0 public int getOrganizationCount(){ log.debug "There are ${organizationCount} organization(s) found." return organizationCount } } Do i need to add an import statement? What do i need to add? Note that the class is located in src/groovy/org/utils. I know that the 'log' variable is accessible in controllers, services, etc. Not sure in 'src' classes. Thanks.

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  • Formatting a query to enumerate through 2 different datatables

    - by boiler1974
    I have 2 datatables sendTable and recvTable They both have identical column names and numbers of columns "NODE" "DSP Name" "BUS" "IDENT" "STATION" "REF1" "REF2" "REF3" "REF4" "REF5" "REF6" "REF7" "REF8" I need to compare these 2 tables and separate out the mismatches I only need to check Columns 3-11 and Ignore col 1 and 2 I tried at first removing the 2 columns and then loop thru row by row and return matches and mismatches but the problem with this approach is that I no longer have the "NODE" and "DSP Name" associated with the row when I finalize my results So I need help with a query Here is my attempt var samerecordQuery = from r1 in sendTable.AsEnumerable() where r1.Field<int>("BUS").Equals(from r2 in recvTable.AsEnumerable() where r2.Field<int>("BUS")) this obviously doesn't work so how do I format the query to say from r1 cols[3-11] equals r2 cols [3-11] and once I have this I can use the except to pull out the mismatches

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  • LINQ2SQL: orderby note.hasChildren(), name ascending

    - by Peter Bridger
    I have a hierarchical data structure which I'm displaying in a webpage as a treeview. I want to data to be ordered to first show nodes ordered alphabetically which have no children, then under these nodes ordered alphabetically which have children. Currently I'm ordering all nodes in one group, which means nodes with children appear next to nodes with no children. I'm using a recursive method to build up the treeview, which has this LINQ code at it's heart: var filteredCategory = from c in category orderby c.Name ascending where c.ParentCategoryId == parentCategoryId && c.Active == true select c; So this is the orderby statement I want to enhance. Shown below is the database table structure: [dbo].[Category]( [CategoryId] [int] IDENTITY(1,1) NOT NULL, [Name] [varchar](100) NOT NULL, [Level] [tinyint] NOT NULL, [ParentCategoryId] [int] NOT NULL, [Selectable] [bit] NOT NULL CONSTRAINT [DF_Category_Selectable] DEFAULT ((1)), [Active] [bit] NOT NULL CONSTRAINT [DF_Category_Active] DEFAULT ((1))

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  • Data Access Layer in an ASP.NET website

    - by user3519124
    :) i have a DAL class file in my project, that my teacher sent me and explained to me but i did not really understand it. It has number of functions, and I understand only few of them, like with connecting to the database or creating a command object but there are 2 that I dont understand: public static DataTable GetTable(string str) { OleDbConnection con = DAL.GetConnection(); OleDbCommand cmd = DAL.GetCommand(con, str); DataTable dt = new DataTable(); OleDbDataAdapter adp = new OleDbDataAdapter(); adp.SelectCommand = cmd; adp.Fill(dt); return dt; } public static int ExecuteNonQuery(string str) { int num = -1; OleDbConnection con = DAL.GetConnection(); con.Open(); if (con.State == ConnectionState.Open) { OleDbCommand cmd = DAL.GetCommand(con, str); num = cmd.ExecuteNonQuery(); con.Close(); } return num; } thank you :)

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  • remote function with pthread

    - by user311130
    Hi all, I wrote some code in c, using pthread (I configured the linker and compiler in eclipse IDE first). #include <pthread.h> #include "starter.h" #include "UI.h" Page* MM; Page* Disk; PCB* all_pcb_array; void* display_prompt(void *id){ printf("Hello111\n"); return NULL; } int main(int argc, char** argv) { printf("Hello\n"); pthread_t *thread = (pthread_t*) malloc (sizeof(pthread_t)); pthread_create(thread, NULL, display_prompt, NULL); printf("Hello\n"); return 1; } that works fine. However, when I move display_prompt to UI.h no "Hello111 " output is printed. anyone know how to solve that? Elad

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  • Boost multiindex complex struct

    - by StrifeLow
    In boost multiindex example complex_structs, it use one key in the car_manufacturer struct for car_table. If car_manufacturer have been modify to have 2 ID struct car_manufacturer { std::string name; int cm_code; car_manufacturer(const std::string& name_, const int& cm_code_):name(name_), cm_code(cm_code_){} }; What will be the key_from_key struct looks like? Have try to add another KeyExtractor or use composite index inside key_from_key, but still cannot compile. Please help on this. Thanks.

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  • dozer custom convertors for primitive types

    - by koti
    the below url has an example on dozer custom convertors.. http://stackoverflow.com/questions/1931212/map-collection-size-in-dozer but when i tried that example its giving the exception like this.. Type: null Source parent class: dozerPackage.Source Source field name: images Source field type: class java.util.ArrayList Source field value: [www, eee] Dest parent class: dozerPackage.Destination Dest field name: numOfImages Dest field type: int org.dozer.MappingException: Destination Type (int) is not accepted by this Custom Converter (dozerPackage.TestCustomFieldConverter)! is there any way that i can return the primitive types from dozer custom convertors..

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  • Why does my program crash after running this particular function?

    - by Tux
    Whenever I type the command to run this function in my program, it runs and then crashes saying: "The application has requested the Runtime to terminate it in an unusal way." Why does it do this? Thanks in advance, Johnny void showInventory(player& obj) { // By Johnny :D std::cout << "\nINVENTORY:\n"; for(int i = 0; i < 20; i++) { std::cout << obj.getItem(i); i++; std::cout << "\t\t\t" << obj.getItem(i) << "\n"; i++; } } std::string getItem(int i) { return inventory[i]; }

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  • Writing booleans to file

    - by Sara
    Hello, I have a piece of code that gives a runtime error. Can anyone help find out why? vector<int> intData; vector<bool> boolData; for(int i=0;i<19000;i++) boolData.push_back(false); string ofile = "tree.dat"; ofstream fout(ofile.c_str(),ios::out | ios::binary); if (!boolData.empty()) fout.write((char *)&boolData[0], sizeof(bool)*boolData.size()); fout.close(); It gives the error when it tries to write the file (fout.write).

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  • What's the standard behaviour for an out parameter when a TryXxxx method returns false?

    - by Matt Lacey
    Assuming a method with the following signature bool TryXxxx(object something, out int toReturn) What is it acceptable for toReturn to be if TryXxxx returns false? In that it's infered that toReturn should never be used if TryXxxx fails does it matter? If toReturn was a nulable type, then it would make sense to return null. But int isn't nullable and I don't want to have to force it to be. If toReturn is always a certain value if TryXxxx fails we risk having the position where 2 values could be considered to indicate the same thing. I can see this leading to potential possible confusion if the 'default' value was returned as a valid response (when TryXxxx returns true). From an implementation point if view it looks like having toReturn be a[ny] value is easiest, but is there anything more important to consider?

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  • Programmatically create static arrays at compile time in C++

    - by Hippicoder
    One can define a static array at compile time as follows: const std::size_t size = 5; unsigned int list[size] = { 1, 2, 3, 4, 5 }; Question 1 - Is it possible by using various kinds of metaprogramming techniques to assign these values "programmatically" at compile time? Question 2 - Assuming all the values in the array are to be the same barr a few, is it possible to selectively assign values at compile time in a programmatic manner? eg: const std::size_t size = 7; unsigned int list[size] = { 0, 0, 2, 3, 0, 0, 0 }; Solutions using C++0x are welcome The array may be quite large, few hundred elements long The array for now will only consist of POD types It can also be assumed the size of the array will be known beforehand, in a static compile-time compliant manner. Solutions must be in C++ (no script or codegen based solutions)

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  • how to check if internal storage file has any data

    - by user3720291
    public class Save extends Activity { int levels = 2; int data_block = 1024; //char[] data = new char[] {'0', '0'}; String blankval = "0"; String targetval = "0"; String temp; String tempwrite; String string = "null"; TextView tex1; TextView tex2; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.save); Intent intent = getIntent(); Bundle b = intent.getExtras(); tex1 = (TextView) findViewById(R.id.textView1); tex2 = (TextView) findViewById(R.id.textView2); if(b!=null) { string =(String) b.get("string"); } loadprev(); save(); } public void save() { if (string.equals("Blank")) blankval = "1"; if (string.equals("Target")) targetval = "1"; temp = blankval + targetval; try { FileOutputStream fos = openFileOutput("data.gds", MODE_PRIVATE); fos.write(temp.getBytes()); fos.close(); } catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} tex1.setText(blankval); tex2.setText(targetval); } public void loadprev() { String final_data = ""; try { FileInputStream fis = openFileInput("data.gds"); InputStreamReader isr = new InputStreamReader(fis); char[] data = new char[data_block]; int size; while((size = isr.read(data))>0) { String read_data = String.copyValueOf(data, 0, size); final_data += read_data; data = new char[data_block]; } } catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} char[] tempread = final_data.toCharArray();; blankval = "" + tempread[0]; targetval = "" + tempread[1]; } } After much tinkering i have finally managed to get my save/load function to work, but it does have an error, pretty much i got it to work then i did a fresh reintall deleting data.gds, afterwards the save/load function crashes because the data.gds file has no previous values. can i use a if statment to check if data.gds has any values in it, if so how do i do it and if not, then what could i use instead?

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  • Java hashcode based on identity

    - by hjfreyer
    The default behavior of Object.hashCode() is to return essentially the "address" of the object so that a.hashCode() == b.hashCode() if and only if a == b. How can I get this behavior in a user-defined class if a superclass already defines hashCode()? For instance: class A { public int hashCode() { return 0; } } class B extends A { public int hashCode() { // Now I want to return a unique hashcode for each object. // In pythonic terms, it'd look something like: return Object.hashCode(this); } } Ideas?

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  • How do I get the sequence of numbers in a sorted-set that are between two integers in clojure?

    - by Greg Rogers
    Say I have a sorted-set of integers, xs, and I want to retrieve all the integers in xs that are [x, y), ie. between x and y. I can do: (select #(and (>= % x) (< % y)) xs) But this is inefficient - O(n) when it could be O(k log n) where k is the number of integers returned. I am just learning clojure so here is how I would do it in C++: set<int>::iterator first = xs.lower_bound(x); set<int>::iterator last = xs.upper_bound(y); for (; first != last; ++first) // do something with *first Can I do this in clojure?

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  • Android library to get pitch from WAV file

    - by Sakura
    I have a list of sampled data from the WAV file. I would like to pass in these values into a library and get the frequency of the music played in the WAV file. For now, I will have 1 frequency in the WAV file and I would like to find a library that is compatible with Android. I understand that I need to use FFT to get the frequency domain. Is there any good libraries for that? I found that [KissFFT][1] is quite popular but I am not very sure how compatible it is on Android. Is there an easier and good library that can perform the task I want? EDIT: I tried to use JTransforms to get the FFT of the WAV file but always failed at getting the correct frequency of the file. Currently, the WAV file contains sine curve of 440Hz, music note A4. However, I got the result as 441. Then I tried to get the frequency of G4, I got the result as 882Hz which is incorrect. The frequency of G4 is supposed to be 783Hz. Could it be due to not enough samples? If yes, how much samples should I take? //DFT DoubleFFT_1D fft = new DoubleFFT_1D(numOfFrames); double max_fftval = -1; int max_i = -1; double[] fftData = new double[numOfFrames * 2]; for (int i = 0; i < numOfFrames; i++) { // copying audio data to the fft data buffer, imaginary part is 0 fftData[2 * i] = buffer[i]; fftData[2 * i + 1] = 0; } fft.complexForward(fftData); for (int i = 0; i < fftData.length; i += 2) { // complex numbers -> vectors, so we compute the length of the vector, which is sqrt(realpart^2+imaginarypart^2) double vlen = Math.sqrt((fftData[i] * fftData[i]) + (fftData[i + 1] * fftData[i + 1])); //fd.append(Double.toString(vlen)); // fd.append(","); if (max_fftval < vlen) { // if this length is bigger than our stored biggest length max_fftval = vlen; max_i = i; } } //double dominantFreq = ((double)max_i / fftData.length) * sampleRate; double dominantFreq = (max_i/2.0) * sampleRate / numOfFrames; fd.append(Double.toString(dominantFreq)); Can someone help me out? EDIT2: I manage to fix the problem mentioned above by increasing the number of samples to 100000, however, sometimes I am getting the overtones as the frequency. Any idea how to fix it? Should I use Harmonic Product Frequency or Autocorrelation algorithms?

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  • Access violation using LocalAlloc()

    - by PaulH
    I have a Visual Studio 2008 Windows Mobile 6 C++ application that is using an API that requires the use of LocalAlloc(). To make my life easier, I created an implementation of a standard allocator that uses LocalAlloc() internally: /// Standard library allocator implementation using LocalAlloc and LocalReAlloc /// to create a dynamically-sized array. /// Memory allocated by this allocator is never deallocated. That is up to the /// user. template< class T, int max_allocations > class LocalAllocator { public: typedef T value_type; typedef size_t size_type; typedef ptrdiff_t difference_type; typedef T* pointer; typedef const T* const_pointer; typedef T& reference; typedef const T& const_reference; pointer address( reference r ) const { return &r; }; const_pointer address( const_reference r ) const { return &r; }; LocalAllocator() throw() : c_( NULL ) { }; /// Attempt to allocate a block of storage with enough space for n elements /// of type T. n>=1 && n<=max_allocations. /// If memory cannot be allocated, a std::bad_alloc() exception is thrown. pointer allocate( size_type n, const void* /*hint*/ = 0 ) { if( NULL == c_ ) { c_ = LocalAlloc( LPTR, sizeof( T ) * n ); } else { HLOCAL c = LocalReAlloc( c_, sizeof( T ) * n, LHND ); if( NULL == c ) LocalFree( c_ ); c_ = c; } if( NULL == c_ ) throw std::bad_alloc(); return reinterpret_cast< T* >( c_ ); }; /// Normally, this would release a block of previously allocated storage. /// Since that's not what we want, this function does nothing. void deallocate( pointer /*p*/, size_type /*n*/ ) { // no deallocation is performed. that is up to the user. }; /// maximum number of elements that can be allocated size_type max_size() const throw() { return max_allocations; }; private: /// current allocation point HLOCAL c_; }; // class LocalAllocator My application is using that allocator implementation in a std::vector< #define MAX_DIRECTORY_LISTING 512 std::vector< WIN32_FIND_DATA, LocalAllocator< WIN32_FIND_DATA, MAX_DIRECTORY_LISTING > > file_list; WIN32_FIND_DATA find_data = { 0 }; HANDLE find_file = ::FindFirstFile( folder.c_str(), &find_data ); if( NULL != find_file ) { do { // access violation here on the 257th item. file_list.push_back( find_data ); } while ( ::FindNextFile( find_file, &find_data ) ); ::FindClose( find_file ); } // data submitted to the API that requires LocalAlloc()'d array of WIN32_FIND_DATA structures SubmitData( &file_list.front() ); On the 257th item added to the vector<, the application crashes with an access violation: Data Abort: Thread=8e1b0400 Proc=8031c1b0 'rapiclnt' AKY=00008001 PC=03f9e3c8(coredll.dll+0x000543c8) RA=03f9ff04(coredll.dll+0x00055f04) BVA=21ae0020 FSR=00000007 First-chance exception at 0x03f9e3c8 in rapiclnt.exe: 0xC0000005: Access violation reading location 0x01ae0020. LocalAllocator::allocate is called with an n=512 and LocalReAlloc() succeeds. The actual Access Violation exception occurs within the std::vector< code after the LocalAllocator::allocate call: 0x03f9e3c8 0x03f9ff04 > MyLib.dll!stlp_std::priv::__copy_trivial(const void* __first = 0x01ae0020, const void* __last = 0x01b03020, void* __result = 0x01b10020) Line: 224, Byte Offsets: 0x3c C++ MyLib.dll!stlp_std::vector<_WIN32_FIND_DATAW,LocalAllocator<_WIN32_FIND_DATAW,512> >::_M_insert_overflow(_WIN32_FIND_DATAW* __pos = 0x01b03020, _WIN32_FIND_DATAW& __x = {...}, stlp_std::__true_type& __formal = {...}, unsigned int __fill_len = 1, bool __atend = true) Line: 112, Byte Offsets: 0x5c C++ MyLib.dll!stlp_std::vector<_WIN32_FIND_DATAW,LocalAllocator<_WIN32_FIND_DATAW,512> >::push_back(_WIN32_FIND_DATAW& __x = {...}) Line: 388, Byte Offsets: 0xa0 C++ MyLib.dll!Foo(unsigned long int cbInput = 16, unsigned char* pInput = 0x01a45620, unsigned long int* pcbOutput = 0x1dabfbbc, unsigned char** ppOutput = 0x1dabfbc0, IRAPIStream* __formal = 0x00000000) Line: 66, Byte Offsets: 0x1e4 C++ If anybody can point out what I may be doing wrong, I would appreciate it. Thanks, PaulH

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  • When does a const return type interfere with template instantiation?

    - by Rimo
    From Herb Sutter's GotW #6 Return-by-value should normally be const for non-builtin return types. ... Note: Lakos (pg. 618) argues against returning const value, and notes that it is redundant for builtins anyway (for example, returning "const int"), which he notes may interfere with template instantiation. While Sutter seems to disagree on whether to return a const value or non-const value when returning an object of a non-built type by value with Lakos, he generally agrees that returning a const value of a built-in type (e.g const int) is not a good idea. While I understand why that is useless because the return value cannot be modified as it is an rvalue, I cannot find an example of how that might interfere with template instantiation. Please give me an example of how having a const qualifier for a return type might interfere with template instantiation.

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  • Policy based design and defaults.

    - by Noah Roberts
    Hard to come up with a good title for this question. What I really need is to be able to provide template parameters with different number of arguments in place of a single parameter. Doesn't make a lot of sense so I'll go over the reason: template < typename T, template <typename,typename> class Policy = default_policy > struct policy_based : Policy<T, policy_based<T,Policy> > { // inherits R Policy::fun(arg0, arg1, arg2,...,argn) }; // normal use: policy_base<type_a> instance; // abnormal use: template < typename PolicyBased > // No T since T is always the same when you use this struct custom_policy {}; policy_base<type_b,custom_policy> instance; The deal is that for many abnormal uses the Policy will be based on one single type T, and can't really be parameterized on T so it makes no sense to take T as a parameter. For other uses, including the default, a Policy can make sense with any T. I have a couple ideas but none of them are really favorites. I thought that I had a better answer--using composition instead of policies--but then I realized I have this case where fun() actually needs extra information that the class itself won't have. This is like the third time I've refactored this silly construct and I've got quite a few custom versions of it around that I'm trying to consolidate. I'd like to get something nailed down this time rather than just fish around and hope it works this time. So I'm just fishing for ideas right now hoping that someone has something I'll be so impressed by that I'll switch deities. Anyone have a good idea? Edit: You might be asking yourself why I don't just retrieve T from the definition of policy based in the template for default_policy. The reason is that default_policy is actually specialized for some types T. Since asking the question I have come up with something that may be what I need, which will follow, but I could still use some other ideas. template < typename T > struct default_policy; template < typename T, template < typename > class Policy = default_policy > struct test : Policy<test<T,Policy>> {}; template < typename T > struct default_policy< test<T, default_policy> > { void f() {} }; template < > struct default_policy< test<int, default_policy> > { void f(int) {} }; Edit: Still messing with it. I wasn't too fond of the above since it makes default_policy permanently coupled with "test" and so couldn't be reused in some other method, such as with multiple templates as suggested below. It also doesn't scale at all and requires a list of parameters at least as long as "test" has. Tried a few different approaches that failed until I found another that seems to work so far: template < typename T > struct default_policy; template < typename T, template < typename > class Policy = default_policy > struct test : Policy<test<T,Policy>> {}; template < typename PolicyBased > struct fetch_t; template < typename PolicyBased, typename T > struct default_policy_base; template < typename PolicyBased > struct default_policy : default_policy_base<PolicyBased, typename fetch_t<PolicyBased>::type> {}; template < typename T, template < typename > class Policy > struct fetch_t< test<T,Policy> > { typedef T type; }; template < typename PolicyBased, typename T > struct default_policy_base { void f() {} }; template < typename PolicyBased > struct default_policy_base<PolicyBased,int> { void f(int) {} };

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  • ASP.NET MVC Persisting mdoel's ID value when Editing

    - by user295017
    public Edit(int? id){ /* Codes */ } [HttpPost] public Edit(Item model){ /* Codes */ } I retrieve a copy of Item in the first Edit method, which would contain a value for ItemID. But when it gets to the HttpPost method, the id value's lost. If switched to public Edit(int? ItemID){ /* Codes */ } [HttpPost] public Edit(Item model){ /* Codes */ } this way ItemID can be persisted in the Item model. But is this a good way to handle it? Will ASP.NET MVC always be able to know that it needs to plug "ItemID" into Item? and are there other ways to persist the ID value? Thanks.

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