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• Partial template specialization on a class

  - by Jonathan Swinney

  I'm looking for a better way to this. I have a chunk of code that needs to handle several different objects that contain different types. The structure that I have looks like this: class Base { // some generic methods } template <typename T> class TypedBase : public Base { // common code with template specialization private: std::map<int,T> mapContainingSomeDataOfTypeT; } template <> class TypedBase<std::string> : public Base { // common code with template specialization public: void set( std::string ); // functions not needed for other types std::string get(); private: std::map<int,std::string> mapContainingSomeDataOfTypeT; // some data not needed for other types } Now I need to add some additional functionality that only applies to one of the derivative classes. Specifically the std::string derivation, but the type doesn't actually matter. The class is big enough that I would prefer not copy the whole thing simply to specialize a small part of it. I need to add a couple of functions (and accessor and modifier) and modify the body of several of the other functions. Is there a better way to accomplish this?

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• Setting up a multi-site CMS, collecting thoughts about the DB schema

  - by Ben Fransen

  Hello all, I'm collecting some thoughts about creating a multisite CMS. In my opinion there are two major approaches. All data is stored into 1 database, giving me the advantage of single point of updates; Seperated databases, so each client has its own database. Giving me the advantage to measure bandwith. Option 1 gives me the disadvantage of measuring bandwith while option is giving me the disadvantage of a single point of update structure. Are there any generic approaches for creating a sort of update system? So my clients can download a small package (maybe a zip with a conf file to tell the updatescript where to put all the files and how to extend the database??) Do you guys have some thougths about the best solution for a situation like this? I have my own webserver, full access to all resources and I'm developing in PHP with MySQL as DBMS. I hope to hear from you and I surely appreciate any effort you make to help me further! Greets from Holland, Ben Fransen

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• C# Why can't I find Sum() of this HashSet. says "Arithmetic operation resulted in an overflow."

  - by user2332665

  I was trying to solve this problem projecteuler,problem125 this is my solution in python(just for understanding the logic) import math lim=10**8 found=set() for start in xrange(1,int(math.sqrt(lim))): sos = start*start for i in xrange(start+1,int(math.sqrt(lim))): sos += (i*i) if sos >= lim: break s=str(int(sos)) if s==s[::-1]: found.add(sos) print sum(found) the same code I wrote in C# is as follows using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication1 { class Program { public static bool isPalindrome(string s) { string temp = ""; for (int i=s.Length-1;i>=0;i-=1){temp+=s[i];} return (temp == s); } static void Main(string[] args) { int lim = Convert.ToInt32(Math.Pow(10,8)); var found = new HashSet<int>(); for (int start = 1; start < Math.Sqrt(lim); start += 1) { int s = start *start; for (int i = start + 1; start < Math.Sqrt(lim); i += 1) { s += i * i; if (s > lim) { break; } if (isPalindrome(s.ToString())) { found.Add(s); } } } Console.WriteLine(found.Sum()); } } } the code debugs fine until it gives an exception at Console.WriteLine(found.Sum()); (line31). Why can't I find Sum() of the set found

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• Extension methods in class library project

  - by Mostafa

  I've implemented some extension methods and put those in separate Class Library project. Imagine I have a simple extension method like this in class library called MD.Utility: namespace MD.Utility { public static class ExtenMethods { public static bool IsValidEmailAddress(this string s) { Regex regex = new Regex(@"^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$"); return regex.IsMatch(s); } } } But nowhere in WebApp like App_code folder or WebFroms code-behind page I can't use this Extension method. If I do like this: using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using MD.Utility; public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { string email = "[email protected]"; if (email.IsValidEmailAddress()) { //To do } } } The compiler doesn't recognize IsValidEmailAddress() and even no intellisense support. While if I put my extension method in App_Code folder it's ok for using in another cs file in App_code Folder or Web Form code-behind pages.

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• Working with images (CGImage), exif data, and file icons

  - by Nick

  What I am trying to do (under 10.6).... I have an image (jpeg) that includes an icon in the image file (that is you see an icon based on the image in the file, as opposed to a generic jpeg icon in file open dialogs in a program). I wish to edit the exif metadata, save it back to the image in a new file. Ideally I would like to save this back to an exact copy of the file (i.e. preserving any custom embedded icons created etc.), however, in my hands the icon is lost. My code (some bits removed for ease of reading): // set up source ref I THINK THE PROBLEM IS HERE - NOT GRABBING THE INITIAL DATA CGImageSourceRef source = CGImageSourceCreateWithURL( (CFURLRef) URL,NULL); // snag metadata NSDictionary *metadata = (NSDictionary *) CGImageSourceCopyPropertiesAtIndex(source,0,NULL); // make metadata mutable NSMutableDictionary *metadataAsMutable = [[metadata mutableCopy] autorelease]; // grab exif NSMutableDictionary *EXIFDictionary = [[[metadata objectForKey:(NSString *)kCGImagePropertyExifDictionary] mutableCopy] autorelease]; << edit exif >> // add back edited exif [metadataAsMutable setObject:EXIFDictionary forKey:(NSString *)kCGImagePropertyExifDictionary]; // get source type CFStringRef UTI = CGImageSourceGetType(source); // set up write data NSMutableData *data = [NSMutableData data]; CGImageDestinationRef destination = CGImageDestinationCreateWithData((CFMutableDataRef)data,UTI,1,NULL); //add the image plus modified metadata PROBLEM HERE? NOT ADDING THE ICON CGImageDestinationAddImageFromSource(destination,source,0, (CFDictionaryRef) metadataAsMutable); // write to data BOOL success = NO; success = CGImageDestinationFinalize(destination); // save data to disk [data writeToURL:saveURL atomically:YES]; //cleanup CFRelease(destination); CFRelease(source); I don't know if this is really a question of image handling, file handing, post-save processing (I could use sip), or me just being think (I suspect the last). Nick

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• Are lambda expressions/delegates in C# "pure", or can they be?

  - by Bob

  I recently asked about functional programs having no side effects, and learned what this means for making parallelized tasks trivial. Specifically, that "pure" functions make this trivial as they have no side effects. I've also recently been looking into LINQ and lambda expressions as I've run across examples many times here on StackOverflow involving enumeration. That got me to wondering if parallelizing an enumeration or loop can be "easier" in C# now. Are lambda expressions "pure" enough to pull off trivial parallelizing? Maybe it depends on what you're doing with the expression, but can they be pure enough? Would something like this be theoretically possible/trivial in C#?: Break the loop into chunks Run a thread to loop through each chunk Run a function that does something with the value from the current loop position of each thread For instance, say I had a bunch of objects in a game loop (as I am developing a game and was thinking about the possibility of multiple threads) and had to do something with each of them every frame, would the above be trivial to pull off? Looking at IEnumerable it seems it only keeps track of the current position, so I'm not sure I could use the normal generic collections to break the enumeration into "chunks". Sorry about this question. I used bullets above instead of pseudo-code because I don't even know enough to write pseudo-code off the top of my head. My .NET knowledge has been purely simple business stuff and I'm new to delegates and threads, etc. I mainly want to know if the above approach is good for pursuing, and if delegates/lambdas don't have to be worried about when it comes to their parallelization.

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• Signals and Variables in VHDL - Problem

  - by Morano88

  I have a signal and this signal is a bitvector. The length of the bitvector depends on an input n, it is not fixed. In order to find the length, I have to do some computations. Can I define a signal after defining the variables ? It is ggiving me errors when I do that. It is working fine If I keep the signal before the variables .. but I don't want that .. the length of Z depends on the computations of the variables. What is the solution ? library IEEE; use IEEE.STD_LOGIC_1164.ALL; use IEEE.STD_LOGIC_ARITH.ALL; use IEEE.STD_LOGIC_UNSIGNED.ALL; entity BSD_Full_Comp is Generic (n:integer:=8); Port(X, Y : inout std_logic_vector(n-1 downto 0); FZ : out std_logic_vector(1 downto 0)); end BSD_Full_Comp; architecture struct of BSD_Full_Comp is Component BSD_BitComparator Port ( Ai_1 : inout STD_LOGIC; Ai_0 : inout STD_LOGIC; Bi_1 : inout STD_LOGIC; Bi_0 : inout STD_LOGIC; S1 : out STD_LOGIC; S0 : out STD_LOGIC ); END Component; Signal Z : std_logic_vector(2*n-3 downto 0); begin ass : process Variable length : integer := n; Variable pow : integer :=0 ; Variable ZS : integer :=0; begin while length /= 0 loop length := length/2; pow := pow+1; end loop; length := 2 ** pow; ZS := length - n; wait; end process; end struct;

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• Changing label content programmatically from within a DataTemplate used in a DataGrid column header

  - by iimpact

  I'm dynamically creating DataGrid columns (based on an event from my ViewModel) and programmatically adding them to an existing DataGrid. Each column uses a generic HeaderTemplate by setting it to a DataTemplate that has been identified in the xaml. The DataTemplate contains two labels in which needs their content needs to be changed upon creation of the DataGrid column. How would this be done? I understand that the DataTemplate uses the ContentPresenter but I am having trouble accessing it within a dynamically created DataGrid column. Code is as follows: xaml: (template used to format the DataGrid column header): <DataTemplate x:Key="columnTemplate"> <StackPanel> <Label Padding="0" Name="labelA"/> <Separator HorizontalAlignment="Stretch"/> <Label Padding="0" Name="labelB"/> </StackPanel> </DataTemplate> c#: (used to dynamically create a DataGrid column and add it to an existing DataGrid) var dataTemplate = FindResource("columnTemplate") as DataTemplate; var column = new DataGridTextColumn(); column.HeaderTemplate = dataTemplate; DataGrid1.Columns.Add(column); I would like to then access both labelA and labelB and change the content.

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• how to verify browser IP for server-side web service

  - by Anthony

  I have a web service that needs to be able to verify the end-user's IP that called the server-script that is requesting the web service. Simple layout: Person A goes to Webpage B. Webpage B calls Web Service C to get some info on Person A. Web Service C won't give Webpage B the requested information without confirmation that the request originated from Person A's IP and not someone who has stolen Person A's session. I'm thinking that for a browser-based solution, the original site (Webpage B) can open an iframe that goes to the Web Service's authentication page. A key of some kind is passed to the browser which will some how indicate both the user's IP and Web Page B's IP, so that the Web Service can confirm that no one has nabbed anything. I have two challenges, but I'll stick to the more immediate one first: I'm not sure if my browser-based plan really makes sense. If someone steals the session cookie, how is the Web Service going to know? Would this cookie be held be Web Page B and thus be harder to steal? Is it a sound assumption that a cookie or key held by the server only and not the browser is safe? Also, would the web service, based on the iframe initial connection, be expecting the server/user-ip combo? What I mean is, does the session key provided via the iframe get stored by the web service and the Web Site B shows it has a match? Or is the session key more generic, meaning the web service is passed the key by Website B and the Web Service verifies that this is a valid session key based on what a valid session key should look like?

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• Constructing human readable sentences based on a survey

  - by Joshua

  The following is a survey given to course attendees to assess an instructor at the end of the course. Communication Skills 1. The instructor communicated course material clearly and accurately. Yes No 2. The instructor explained course objectives and learning outcomes. Yes No 3. In the event of not understanding course materials the instructor was available outside of class. Yes No 4. Was instructor feedback and grading process clear and helpful? Yes No 5. Do you feel that your oral and written skills have improved while in this course? Yes No We would like to summarize each attendees selection based on the choices chosen by him. If the provided answers were [No, No, Yes, Yes, Yes]. Then we would summarize this as "The instructor was not able to summarize course objectives and learning outcomes clearly, but was available for usually helpful outside of class. The instructor feedback and grading process was clear and helpful and I feel that my oral and written skills have improved because of this course. Based on the selections chosen by the attendee the summary would be quite different. This leads to many answers based on the choices selected and the number of such questions in the survey. The questions are usually provided by the training organization. How do you come up with a generic solution so that this can be effectively translated into a human readable form. I am looking for tools or libraries (java based), suggestions which will help me create such human readable output. I would like to hide the complexity from the end users as much as possible.

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• C#, finding the largest prime factor of a number

  - by Juan

  Hello! I am new at programming and I am practicing my C# programming skills. My application is meant to find the largest prime factor of a number entered by the user. But my application is not returning the right answer and I dont really know where the problem is. Can you please help me? using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Console.WriteLine("Calcular máximo factor primo de n. De 60 es 5."); Console.Write("Escriba un numero: "); long num = Convert.ToInt64(Console.ReadLine()); long mfp = maxfactor(num); Console.WriteLine("El maximo factor primo es: " + num); Console.Read(); } static private long maxfactor (long n) { long m=1 ; bool en= false; for (long k = n / 2; !en && k > 1; k--) { if (n % k == 0 && primo(k)) { m = k; en = true; } } return m; } static private bool primo(long x) { bool sp = true; for (long i = 2; i <= x / 2; i++) { if (x % i == 0) sp = false; } return sp; } } }

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• Elegant way to take basename of directory in Python?

  - by user248237

  I have several scripts that take as input a directory name, and my program creates files in those directories. Sometimes I want to take the basename of a directory given to the program and use it to make various files in the directory. For example, # directory name given by user via command-line output_dir = "..." # obtained by OptParser, for example my_filename = output_dir + '/' + os.path.basename(output_dir) + '.my_program_output' # write stuff to my_filename The problem is that if the user gives a directory name with a trailing slash, then os.path.basename will return the empty string, which is not what I want. What is the most elegant way to deal with these slash/trailing slash issues in python? I know I can manually check for the slash at the end of output_dir and remove it if it's there, but there seems like there should be a better way. Is there? Also, is it OK to manually add '/' characters? E.g. output_dir + '/' os.path.basename() or is there a more generic way to build up paths? Thanks.

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• Lazy non-modifiable list in Google Collections

  - by mindas

  I was looking for a decent implementation of a generic lazy non-modifiable list implementation to wrap my search result entries. The unmodifiable part of the task is easy as it can be achieved by Collections.unmodifiableList() so I only need to sort out the the lazy part. Surprisingly, google-collections doesn't have anything to offer; while LazyList from Apache Commons Collections does not support generics. I have found an attempt to build something on top of google-collections but it seems to be incomplete (e.g. does not support size()), outdated (does not compile with 1.0 final) and requiring some external classes, but could be used as a good starting point to build my own class. Is anybody aware of any good implementation of a LazyList? If not, which option do you think is better: write my own implementation, based on google-collections ForwardingList, similar to what Peter Maas did; write my own wrapper around Commons Collections LazyList (the wrapper would only add generics so I don't have to cast everywhere but only in the wrapper itself); just write something on top of java.util.AbstractList; Any other suggestions are welcome.

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• Change in behaviour & generation of nullreference exception

  - by peril brain

  I made this program 2hr ago and it ran quit well when i confronted this to presaved .xls file. But when i closed that and started new instance,it started generating null refrence exception why??plz explain. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; using System.Threading; using Microsoft.Office.Interop; using Excel = Microsoft.Office.Interop.Excel; namespace svchost { class MainClass { Excel.Application oExcelApp; static void Main(string[] args) { MainClass mc = new MainClass(); while (true) { if (mc.chec()) { Console.WriteLine("RUNNING"); Thread.Sleep(4000); } else { Console.WriteLine("NOT RUNNING"); Thread.Sleep(8000); } } } public bool chec() { try { oExcelApp = (Excel.Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application"); Excel.Workbook xlwkbook = (Excel.Workbook)oExcelApp.ActiveWorkbook; //****PROBLEM FROM HERE********* Console.WriteLine(xlwkbook.Name + "\n"); ke kw = new ke(ref oExcelApp,ref xlwkbook); Console.WriteLine(xlwkbook.Author); xlwkbook = null; } catch (Exception ec) { oExcelApp = null; System.GC.Collect(); Console.WriteLine(ec); return false; } oExcelApp = null; System.GC.Collect(); return true; } } class ke { public ke(ref Excel.Application a1, ref Excel.Workbook b1) { Excel.Worksheet ws = (Excel.Worksheet)a1.ActiveSheet; Console.WriteLine(a1.ActiveWorkbook.Name + "\n" + ws.Name); Excel.Range rn; rn = ws.Cells.Find("657/07", Type.Missing, Excel.XlFindLookIn.xlValues, Excel.XlLookAt.xlPart, Excel.XlSearchOrder.xlByRows, Excel.XlSearchDirection.xlNext, false, Type.Missing, Type.Missing); Console.WriteLine(rn.Text); } } }

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• My First F# program

  - by sudaly

  Hi I just finish writing my first F# program. Functionality wise the code works the way I wanted, but not sure if the code is efficient. I would much appreciate if someone could review the code for me and point out the areas where the code can be improved. Thanks Sudaly open System open System.IO open System.IO.Pipes open System.Text open System.Collections.Generic open System.Runtime.Serialization [<DataContract>] type Quote = { [<field: DataMember(Name="securityIdentifier") >] RicCode:string [<field: DataMember(Name="madeOn") >] MadeOn:DateTime [<field: DataMember(Name="closePrice") >] Price:float } let m_cache = new Dictionary<string, Quote>() let ParseQuoteString (quoteString:string) = let data = Encoding.Unicode.GetBytes(quoteString) let stream = new MemoryStream() stream.Write(data, 0, data.Length); stream.Position <- 0L let ser = Json.DataContractJsonSerializer(typeof<Quote array>) let results:Quote array = ser.ReadObject(stream) :?> Quote array results let RefreshCache quoteList = m_cache.Clear() quoteList |> Array.iter(fun result->m_cache.Add(result.RicCode, result)) let EstablishConnection() = let pipeServer = new NamedPipeServerStream("testpipe", PipeDirection.InOut, 4) let mutable sr = null printfn "[F#] NamedPipeServerStream thread created, Wait for a client to connect" pipeServer.WaitForConnection() printfn "[F#] Client connected." try // Stream for the request. sr <- new StreamReader(pipeServer) with | _ as e -> printfn "[F#]ERROR: %s" e.Message sr while true do let sr = EstablishConnection() // Read request from the stream. printfn "[F#] Ready to Receive data" sr.ReadLine() |> ParseQuoteString |> RefreshCache printfn "[F#]Quot Size, %d" m_cache.Count let quot = m_cache.["MSFT.OQ"] printfn "[F#]RIC: %s" quot.RicCode printfn "[F#]MadeOn: %s" (String.Format("{0:T}",quot.MadeOn)) printfn "[F#]Price: %f" quot.Price

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• Erlang, SSH and authorized_keys

  - by Roberto Aloi

  Playing with the ssh and public_key application in Erlang, I've discovered a nice feature. I was trying to connect to my running Erlang SSH daemon by using a rsa key, but the authentication was failing and I was prompted for a password. After some debugging and tracing (and a couple of coffees), I've realized that, for some weird reason, a non valid key for my user was there. The authorized_keys file contained two keys. The wrong one was at some point in the file, while the correct one was appended at the end of the file. Now, the Erlang SSH application, when diffing the provided key with the ones contained in the authorized_keys, it was finding the first entry (completely ignoring the second on - the correct one). Then, it was switching to different authentication mechanism (at first it was trying dsa instead of rsa and then it was prompting for a password). The question is: Is this behavior intended or should the SSH server check for multiple entries for the same user in the *authorized_keys* file? Is this a generic SSH behaviour or it's just specific to the Erlang implementation?

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• How to get rid of void-pointers.

  - by Patrick

  I inherited a big application that was originally written in C (but in the mean time a lot of C++ was also added to it). Because of historical reasons, the application contains a lot of void-pointers. Before you start to choke, let me explain why this was done. The application contains many different data structures, but they are stored in 'generic' containers. Nowadays I would use templated STL containers for it, or I would give all data structures a common base class, so that the container can store pointers to the base class, but in the [good?] old C days, the only solution was to cast the struct-pointer to a void-pointer. Additionally, there is a lot of code that works on these void-pointers, and uses very strange C constructions to emulate polymorphism in C. I am now reworking the application, and trying to get rid of the void-pointers. Adding a common base-class to all the data structures isn't that hard (few days of work), but the problem is that the code is full of constructions like shown below. This is an example of how data is stored: void storeData (int datatype, void *data); // function prototype ... Customer *myCustomer = ...; storeData (TYPE_CUSTOMER, myCustomer); This is an example of how data is fetched again: Customer *myCustomer = (Customer *) fetchData (int datatype, char *key); I actually want to replace all the void-pointers with some smart-pointer (reference-counted), but I can't find a trick to automate (or at least) help me to get rid of all the casts to and from void-pointers. Any tips on how to find, replace, or interact in any possible way with these conversions?

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• How can I create a dynamic LINQ query in C# with possible multiple group by clauses?

  - by FordPrefect141

  I have been a programmer for some years now but I am a newcomer to LINQ and C# so forgive me if my question sounds particularly stupid. I hope someone may be able to point me in the right direction. My task is to come up with the ability to form a dynamic multiple group by linq query within a c# script using a generic list as a source. For example, say I have a list containing multiple items with the following structure: FieldChar1 - character FieldChar2 - character FieldChar3 - character FieldNum1 - numeric FieldNum2 - numeric In a nutshell I want to be able to create a LINQ query that will sum FieldNum1 and FieldNum2 grouped by any one, two or all three of the FieldChar fields that will be decided at runtime depending on the users requirements as well as selecting the FieldChar fields in the same query. I have the dynamic.cs in my project which icludes a GroupByMany extension method but I have to admit I am really not sure how to put these to use. I am able to get the desired results if I use a query with hard-wired group by requests but not dynamically. Apologies for any erroneous nomenclature, I am new to this language but any advice would be most welcome. Many thanks Alex

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• C# Regex stops after first line matched

  - by JD Guzman

  Ok so I have a regex and I need it to find matches in a multiline string. This is the string I am using: Device Identifier: disk0 Device Node: /dev/disk0 Part of Whole: disk0 Device / Media Name: OCZ-VERTEX2 Media Volume Name: Not applicable (no file system) Mounted: Not applicable (no file system) File System: None Content (IOContent): GUID_partition_scheme OS Can Be Installed: No Media Type: Generic Protocol: SATA SMART Status: Verified Total Size: 240.1 GB (240057409536 Bytes) (exactly 468862128 512-Byte-Blocks) Volume Free Space: Not applicable (no file system) Device Block Size: 512 Bytes Read-Only Media: No Read-Only Volume: Not applicable (no file system) Ejectable: No Whole: Yes Internal: Yes Solid State: Yes OS 9 Drivers: No Low Level Format: Not supported Basically I need to separate each line into two groups with the colon as the separator. The regex I am using is: @"([A-Za-z0-9\(\) \-\/]+):([A-Za-z0-9\(\) \-\/]+).*" It does work but only picks up the first line and separates it into the two groups like I want but it stops at that point. I have tried the Multiline option but it doesn't make any difference. I must admit I am new to the regex world. Any help is appreciated.

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• Retrive data from two tables in asp.net mvc using ADO.Net Entity Framework

  - by user192972

  Please read my question carefully and reply me. I have two tables as table1 and table2. In table1 i have columns as AddressID(Primary Key),Address1,Address2,City In table2 i have columns as ContactID(Primary Key),AddressID(Foriegn Key),Last Name,First Name. By using join operation i can retrive data from both the tables. I created a Model in my MVC Application.I can see both the tables in enitity editor. In the ViewData folder of my solution explorer i created two class as ContactViewData.cs and SLXRepository.cs In the ContactViewData.cs i have following code public IEnumerable<CONTACT> contacts { get; set; } In the SLXRepository.cs i have following code public IEnumerable<CONTACT> GetContacts() { var contact = ( from c in context.CONTACT join a in context.ADDRESS on c.ADDRESSID equals a.ADDRESSID select new { a.ADDRESS1, a.ADDRESS2, a.CITY, c.FIRSTNAME, c.LASTNAME } ); return contact; } I am getting the error in return type Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Collections.Generic.IEnumerable'. An explicit conversion exists (are you missing a cast?)

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• Comparable and Comparator contract with regards to null

  - by polygenelubricants

  Comparable contract specifies that e.compareTo(null) must throw NullPointerException. From the API: Note that null is not an instance of any class, and e.compareTo(null) should throw a NullPointerException even though e.equals(null) returns false. On the other hand, Comparator API mentions nothing about what needs to happen when comparing null. Consider the following attempt of a generic method that takes a Comparable, and return a Comparator for it that puts null as the minimum element. static <T extends Comparable<? super T>> Comparator<T> nullComparableComparator() { return new Comparator<T>() { @Override public int compare(T el1, T el2) { return el1 == null ? -1 : el2 == null ? +1 : el1.compareTo(el2); } }; } This allows us to do the following: List<Integer> numbers = new ArrayList<Integer>( Arrays.asList(3, 2, 1, null, null, 0) ); Comparator<Integer> numbersComp = nullComparableComparator(); Collections.sort(numbers, numbersComp); System.out.println(numbers); // "[null, null, 0, 1, 2, 3]" List<String> names = new ArrayList<String>( Arrays.asList("Bob", null, "Alice", "Carol") ); Comparator<String> namesComp = nullComparableComparator(); Collections.sort(names, namesComp); System.out.println(names); // "[null, Alice, Bob, Carol]" So the questions are: Is this an acceptable use of a Comparator, or is it violating an unwritten rule regarding comparing null and throwing NullPointerException? Is it ever a good idea to even have to sort a List containing null elements, or is that a sure sign of a design error?

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• Assembly reference from ASP.NET App_Code directory

  - by Gerald Schneider

  I have trouble getting a custom ObjectDataSource for an asp:ListView control to work. I have the class for the DataSource in the App_Code directory of the web application (as required by the asp:ListView control). using System; using System.Collections.Generic; using System.ComponentModel; using System.Configuration; using System.Data; using System.Data.Common; using System.Web; using System.DirectoryServices; [DataObject] public class UsersDAL { [DataObjectMethod(DataObjectMethodType.Select)] public List<User> LoadAll(int startIndex, int maxRows, string sortedBy) { List<User> users = new List<User>(); DirectoryEntry entry; return users; } } As soon as I add using System.DirectoryServices; the page crashes with this message: Compiler Error Message: CS0234: The type or namespace name 'DirectoryServices' does not exist in the namespace 'System' (are you missing an assembly reference?) Without the usage of System.DirectoryServices the page loads without problems. The reference is there, it is working in classes outside the App_Code directory.

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• A copy of ApplicationController has been removed from the module tree but is still active

  - by Matchu

  Whenever two concurrent HTTP requests go to my Rails app, the second always returns the following error: A copy of ApplicationController has been removed from the module tree but is still active! From there it gives an unhelpful stack trace to the effect of "we went through the standard server stuff, ran your first before_filter on ApplicationController (and I checked; it's just whichever filter runs first)", then offers the following: /home/matchu/rails/torch/vendor/rails/activesupport/lib/active_support/dependencies.rb:414:in `load_missing_constant' /home/matchu/rails/torch/vendor/rails/activesupport/lib/active_support/dependencies.rb:96:in `const_missing' which I'm assuming is a generic response and doesn't really say much. Google seems to tell me that people developing Rails Engines will encounter this, but I don't do that. All I've done is upgrade my Rails app from 2.2 (2.1?) to 2.3. What are some possible causes for this error, and how can I go about tracking down what's really going on? I know this question is vague, so would any other information be helpful? More importantly: I tried doing a test run in a "production" environment just now, and the error doesn't seem to persist. Does this only affect development, then, and need I not worry too much?

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• SQL Express under IIS 7.5

  - by fampinheiro

  I´m developing a web service that access a SQL Express database, it works very well in the Visual Studio host but when i deploy it to IIS 7.5 i get this exception. Please help me. Stack Trace: System.Data.EntityException: The underlying provider failed on Open. ---> System.Data.SqlClient.SqlException: Failed to generate a user instance of SQL Server due to failure in retrieving the user's local application data path. Please make sure the user has a local user profile on the computer. The connection will be closed. at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) at System.Data.SqlClient.SqlInternalConnectionTds.CompleteLogin(Boolean enlistOK) at System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject) at System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart) at System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance) at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance) at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection) at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options) at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject) at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject) at System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) at System.Data.SqlClient.SqlConnection.Open() at System.Data.EntityClient.EntityConnection.OpenStoreConnectionIf(Boolean openCondition, DbConnection storeConnectionToOpen, DbConnection originalConnection, String exceptionCode, String attemptedOperation, Boolean& closeStoreConnectionOnFailure) --- End of inner exception stack trace --- at System.Data.EntityClient.EntityConnection.OpenStoreConnectionIf(Boolean openCondition, DbConnection storeConnectionToOpen, DbConnection originalConnection, String exceptionCode, String attemptedOperation, Boolean& closeStoreConnectionOnFailure) at System.Data.EntityClient.EntityConnection.Open() at System.Data.Objects.ObjectContext.EnsureConnection() at System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption) at System.Data.Objects.ObjectQuery`1.System.Collections.Generic.IEnumerable<T>.GetEnumerator() at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source) at WSCinema.CinemaService.Movie() in D:\Documents\My Dropbox\Projects\sd.v0910\trab3\code\WSCinema\CinemaService.asmx.cs:line 46

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• Silverlight RIA Services - how to do Windows Authentication?

  - by Gustavo Cavalcanti

  I am building my first Silverlight 3 + RI Services application and need some help. It will be deployed in an controlled corporate intranet, 100% windows clients. I have started from the Silverlight Business Application template. These are my requirements: Upon launch the application needs to recognize the currently logged-in user. The application needs to have access to other properties of the user in AD, such as email, full name, and group membership. Group membership is used to grand certain features in the application. A "login as a different user" link is to be always available - Some machines are available throughout the enterprise, logged-in as a certain generic user (verified by the absence of certain membership groups). In this case one can enter credentials and log in (impersonate) to the application as a user different from the one already logged-into the machine. This user is to be used in service calls I have modified the following in the default Business Application template: App.xaml: appsvc:WindowsAuthentication instead of the default FormsAuthentication Web.config: authentication mode="Windows" With these modifications I resolve requirement #1 (get the currently logged-in user). But when I examine RiaContext.Current.User, I don't have access to other properties from AD, such as group memberships. How can I achieve my other requirements? Thanks for your help.

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