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  • Cast Object to Generic List

    - by CrazyJoe
    I have 3 generict type list. List<Contact> = new List<Contact>(); List<Address> = new List<Address>(); List<Document> = new List<Document>(); And save it on a variable with type object. Now i nedd do Cast Back to List to perfom a foreach, some like this: List<Contact> = (List<Contact>)obj; But obj content change every time, and i have some like this: List<???> = (List<???>)obj; I have another variable holding current obj Type: Type t = typeof(obj); Can i do some thing like that??: List<t> = (List<t>)obj; Obs: I no the current type in the list but i need to cast , and i dont now another form instead: List<Contact> = new List<Contact>(); Help Plz!!!

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  • Dynamic/Generic ViewModelBase?

    - by Shimmy
    I am learning MVVM now and I understand few things (more than but few are here..): Does every model potentially exposed (thru a VM) to the View is having a VM? For example, if I have a Contact and Address entity and each contact has an Addresses (many) property, does it mean I have to create a ContactViewModel and an AddressViewModel etc.? Do I have to redeclare all the properties of the Model again in the ViewModel (i.e. FirstName, LastName blah blah)? why not have a ViewModelBase and the ContactViewMode will be a subclass of ViewModelBase accessing the Entity's properties itself? and if this is a bad idea that the View has access to the entity (please explain why), then why not have the ViewModelBase be a DynamicObject (view the Dictionary example @ the link page), so I don't have to redeclare all the properties and validation over and over in the two tiers (M & VM) - because really, the View is anyway accessing the ViewModel's fields via reflection anyway. I think MVVM was the hardest technology I've ever learned. it doesn't have out-the-box support and there are to many frameworks and methods to achieve it, and in the other hand there is no arranged way to learn it (as MVC for instance), learning MVVM means browsing and surfing around trying to figure out what's better. Bottom line, what I mean by this section is please go and vote to MSFT to add MVVM support in the BCL and generators for VMs and Vs according to the Ms. Thanks

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  • Converting generic type to it's base and vice-versa

    - by Pajci
    Can someone help me with the conversion I am facing in enclosed code ... I commented the lines of code, where I am having problem. Is this even the right way to achieve this ... what I am trying to do, is forward responses of specified type to provided callback. public class MessageBinder { private class Subscriber<T> : IEquatable<Subscriber<T>> where T : Response { ... } private readonly Dictionary<Type, List<Subscriber<Response>>> bindings; public MessageBinder() { this.bindings = new Dictionary<Type, List<Subscriber<Response>>>(); } public void Bind<TResponse>(short shortAddress, Action<ZigbeeAsyncResponse<TResponse>> callback) where TResponse : Response { List<Subscriber<TResponse>> subscribers = this.GetSubscribers<TResponse>(); if (subscribers != null) { subscribers.Add(new Subscriber<TResponse>(shortAddress, callback)); } else { var subscriber = new Subscriber<TResponse>(shortAddress, callback); // ERROR: cannot convert from 'List<Subscriber<TResponse>>' to 'List<Subscriber<Response>>' ... tried LINQ Cast operator - does not work either this.bindings.Add(typeof(TResponse), new List<Subscriber<TResponse>> { subscriber }); } } public void Forward<TResponse>(TResponse response) where TResponse : Response { var subscribers = this.GetSubscribers<TResponse>(); if (subscribers != null) { Subscriber<TResponse> subscriber; Type responseType = typeof (TResponse); if (responseType.IsSubclassOf(typeof (AFResponse))) { // ERROR: Cannot convert type 'TResponse' to 'AFResponse' ... tried cast to object first, works, but is this the right way? var afResponse = (AFResponse)response; subscriber = subscribers.SingleOrDefault(s => s.ShortAddress == afResponse.ShortAddress); } else { subscriber = subscribers.First(); } if (subscriber != null) { subscriber.Forward(response); } } } private List<Subscriber<TResponse>> GetSubscribers<TResponse>() where TResponse : Response { List<Subscriber<Response>> subscribers; this.bindings.TryGetValue(typeof(TResponse), out subscribers); // ERROR: How can I cast List<Subscriber<Response>> to List<Subscriber<TResponse>>? return subscribers; } } Thank you for any help :)

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  • I have a generic implementation of PHP mcrypt module and its not decrypting

    - by Ken Mitchner
    class Crypt_Data { protected $_mcrypt=null; protected $_iv=null; protected $_key=null; public function __construct() { $this->_mcrypt = mcrypt_module_open('rijndael_256', '', 'cbc', ''); $key_size = mcrypt_enc_get_key_size($this->_mcrypt); for($i=0;$i<$key_size;$i++) $test_key .= "0"; $this->_iv = $test_key; $this->_key = $test_key; mcrypt_generic_init($this->_mcrypt,$this->_key,$this->_iv); } public function dataEncrypt($data) { return base64_encode(mcrypt_generic($this->_mcrypt, $data)); } public function dataDecrypt($data) { return mdecrypt_generic($this->_mcrypt, base64_decode($data)); } } $crypt = new Crypt_Data(); $string = "encrypt me"; $encrypted = $crypt->dataEncrypt($string); echo $encrypted."<BR>"; $decrypted = $crypt->dataDecrypt($encrypted); echo $decrypted."<BR>"; output: JJKfKxZckkqwfZ5QWeyVR+3PkMQAsP0Gr1hWaygV20I= qÌÌi_ÖZí(®`iÜ¥wÝÿ ô0€Í6Ÿhf[%ër No idea why this isn't working, everything seems to be fine on my end.. i tried decrypting it with mcrypt_cbc(); and it decrypted it properly.. so it has something to do with my mdecrypt_generic.. any ideas?

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  • What are the advantages of learning Go?

    - by Pangea
    What is so unique about Go? Over the 11 years of my career I've learnt Pascal, C, C++, COBOL and then Java. I always felt that going from C to C++ to Java was a incremental and value added progression. Now I see a proliferation of functional programming languages and I understand the benefit of learning few of them (like actors in scala etc). Now I was going through the Go programming language and was wondering why would I want to learn this? Is this going to simplify how I have been writing the code? What are its use cases? How can I make a case to promote it in my team? What is the next programming language that a Java team that builds business applications like us can benefit from? Appreciate your comments on this.

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  • How to bind a ComboBox to generic dictionary with xaml code

    - by MMD MNC
    I'm using the following code : private Dictionary<string, string> GetNumber { get; set; } public ReportsLetterTra() { GetMonth = new Dictionary<string, string> { {"1", "First"}, {"2", "Second"} }; InitializeComponent(); } xaml code : <ComboBox DisplayMemberPath="value" SelectedValuePath="key" ItemsSource="{Binding ElementName=reportslettra,Path=GetNumber}" SelectedIndex="0" Name="cmbFromNumber" /> Why is not bind GetNumber to cmbFromNumber?!

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  • Wildcards vs. generic methods

    - by FredOverflow
    Is there any practical difference between the following approaches to print all elements in a range? public static void printA(Iterable<?> range) { for (Object o : range) { System.out.println(o); } } public static <T> void printB(Iterable<T> range) { for (T x : range) { System.out.println(x); } } Apparently, printB involves an additional checked cast to Object (see line 16), which seems rather stupid to me -- isn't everything an Object anyway? public static void printA(java.lang.Iterable); Code: 0: aload_0 1: invokeinterface #18, 1; //InterfaceMethod java/lang/Iterable.iterator:()Ljava/util/Iterator; 6: astore_2 7: goto 24 10: aload_2 11: invokeinterface #24, 1; //InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object; 16: astore_1 17: getstatic #30; //Field java/lang/System.out:Ljava/io/PrintStream; 20: aload_1 21: invokevirtual #36; //Method java/io/PrintStream.println:(Ljava/lang/Object;)V 24: aload_2 25: invokeinterface #42, 1; //InterfaceMethod java/util/Iterator.hasNext:()Z 30: ifne 10 33: return public static void printB(java.lang.Iterable); Code: 0: aload_0 1: invokeinterface #18, 1; //InterfaceMethod java/lang/Iterable.iterator:()Ljava/util/Iterator; 6: astore_2 7: goto 27 10: aload_2 11: invokeinterface #24, 1; //InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object; 16: checkcast #3; //class java/lang/Object 19: astore_1 20: getstatic #30; //Field java/lang/System.out:Ljava/io/PrintStream; 23: aload_1 24: invokevirtual #36; //Method java/io/PrintStream.println:(Ljava/lang/Object;)V 27: aload_2 28: invokeinterface #42, 1; //InterfaceMethod java/util/Iterator.hasNext:()Z 33: ifne 10 36: return

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  • Experiences with D-programming-language

    - by Dario
    Has someone here ever had experience with the D programming language? It seems to have many nice features but will it ever reach the popularity of those currently widespread languages like C++, Java or C#? So is it worth learning or is it an isolated language with minor prospects.

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  • Thread Safety of C# List<T> for readers

    - by ILIA BROUDNO
    I am planning to create the list once in a static constructor and then have multiple instances of that class read it (and enumerate through it) concurrently without doing any locking. In this article http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx MS describes the issue of thread safety as follows: Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe. A List can support multiple readers concurrently, as long as the collection is not modified. Enumerating through a collection is intrinsically not a thread-safe procedure. In the rare case where an enumeration contends with one or more write accesses, the only way to ensure thread safety is to lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization. The "Enumerating through a collection is intrinsically not a thread-safe procedure." Statement is what worries me. Does this mean that it is thread safe for readers only scenario, but as long as you do not use enumeration? Or is it safe for my scenario?

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  • Applying to a international programming jobs

    - by Shawn Mclean
    If this question is not suited at stackoverflow, could you tell me in comments and suggest a site that I can ask this question and I'll close this. I'm located in Jamaica and in my final semester of a bsc computer science degree. I would like to apply to programming jobs abroad. How do I go about this? What is the sequence to follow and documents needed? Thanks.

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  • Overloading generic implicit conversions

    - by raichoo
    Hi I'm having a little scala (version 2.8.0RC1) problem with implicit conversions. Whenever importing more than one implicit conversion the first one gets shadowed. Here is the code where the problem shows up: // containers class Maybe[T] case class Nothing[T]() extends Maybe[T] case class Just[T](value: T) extends Maybe[T] case class Value[T](value: T) trait Monad[C[_]] { def >>=[A, B](a: C[A], f: A => C[B]): C[B] def pure[A](a: A): C[A] } // implicit converter trait Extender[C[_]] { class Wrapper[A](c: C[A]) { def >>=[B](f: A => C[B])(implicit m: Monad[C]): C[B] = { m >>= (c, f) } def >>[B](b: C[B])(implicit m: Monad[C]): C[B] = { m >>= (c, { (x: A) => b } ) } } implicit def extendToMonad[A](c: C[A]) = new Wrapper[A](c) } // instance maybe object maybemonad extends Extender[Maybe] { implicit object MaybeMonad extends Monad[Maybe] { override def >>=[A, B](a: Maybe[A], f: A => Maybe[B]): Maybe[B] = { a match { case Just(x) => f(x) case Nothing() => Nothing() } } override def pure[A](a: A): Maybe[A] = Just(a) } } // instance value object identitymonad extends Extender[Value] { implicit object IdentityMonad extends Monad[Value] { override def >>=[A, B](a: Value[A], f: A => Value[B]): Value[B] = { a match { case Value(x) => f(x) } } override def pure[A](a: A): Value[A] = Value(a) } } import maybemonad._ //import identitymonad._ object Main { def main(args: Array[String]): Unit = { println(Just(1) >>= { (x: Int) => MaybeMonad.pure(x) }) } } When uncommenting the second import statement everything goes wrong since the first "extendToMonad" is shadowed. However, this one works: object Main { implicit def foo(a: Int) = new { def foobar(): Unit = { println("Foobar") } } implicit def foo(a: String) = new { def foobar(): Unit = { println(a) } } def main(args: Array[String]): Unit = { 1 foobar() "bla" foobar() } } So, where is the catch? What am I missing? Regards, raichoo

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  • Iterating over member typed collection fails when using untyped reference to generic object

    - by Alexander Pavlov
    Could someone clarify why iterate1() is not accepted by compiler (Java 1.6)? I do not see why iterate2() and iterate3() are much better. This paragraph is added to avoid silly "Your post does not have much context to explain the code sections; please explain your scenario more clearly." protection. import java.util.Collection; import java.util.HashSet; public class Test<T> { public Collection<String> getCollection() { return new HashSet<String>(); } public void iterate1(Test test) { for (String s : test.getCollection()) { // ... } } public void iterate2(Test test) { Collection<String> c = test.getCollection(); for (String s : c) { // ... } } public void iterate3(Test<?> test) { for (String s : test.getCollection()) { // ... } } } Compiler output: $ javac Test.java Test.java:11: incompatible types found : java.lang.Object required: java.lang.String for (String s : test.getCollection()) { ^ Note: Test.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. 1 error

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  • generic function for extracting values from an array with one particular key in PHP

    - by Sabya
    Is it possible in PHP to extract values from an array with a particular key path and return an array of those values? I'll explain with an example: $user = array ( array( id => 1, email =>'[email protected]', project => array ('project_id' => 222, 'project_name' => 'design') ), array( id => 2, email =>'[email protected]', project => array ('project_id' => 333, 'project_name' => 'design') ) ); /** I have to write a function something like: */ $projectIds = extractValuesWithKey($user, array('project', 'project_id')); print_r($projectIds); Output: Array( [0] => 222, [1] => 333 )

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  • Linq generic Expression in query on "element" or on IQueryable (multiple use)

    - by Bogdan Maxim
    Hi, I have the following expression public static Expression<Func<T, bool>> JoinByDateCheck<T>(T entity, DateTime dateToCheck) where T : IDateInterval { return (entityToJoin) => entityToJoin.FromDate.Date <= dateToCheck.Date && (entityToJoin.ToDate == null || entityToJoin.ToDate.Value.Date >= dateToCheck.Date); } IDateInterval interface is defined like this: interface IDateInterval { DateTime FromDate {get;} DateTime? ToDate {get;} } and i need to apply it in a few ways: (1) Query on Linq2Sql Table: var q1 = from e in intervalTable where FunctionThatCallsJoinByDateCheck(e, constantDateTime) select e; or something like this: intervalTable.Where(FunctionThatCallsJoinByDateCheck(e, constantDateTime)) (2) I need to use it in some table joins (as linq2sql doesn't provide comparative join): var q2 = from e1 in t1 join e2 in t2 on e1.FK == e2.PK where OtherFunctionThatCallsJoinByDateCheck(e2, e1.FromDate) or var q2 = from e1 in t1 from e2 in t2 where e1.FK == e2.PK && OtherFunctionThatCallsJoinByDateCheck(e2, e1.FromDate) (3) I need to use it in some queries like this: var q3 = from e in intervalTable.FilterFunctionThatCallsJoinByDateCheck(constantDate); Dynamic linq is not something that I can use, so I have to stick to plain linq. Thank you Clarification: Initially I had just the last method (FilterFunctionThatCallsJoinByDateCheck(this IQueryable<IDateInterval> entities, DateTime dateConstant) ) that contained the code from the expression. The problem is that I get a SQL Translate exception if I write the code in a method and call it like that. All I want is to extend the use of this function to the where clause (see the second query in point 2)

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  • Generic documentation guide-lines for implementation details

    - by mgj
    Hi..:) For documentation and presentation purposes, we often find professionals/students creating SRS, coding guidelines etc. for these things there is some kind of a checklist which one could use to appropriately match what could relate to a specific case and accordingly one does a documentation for each. On those grounds could you please give me some sort of a checklist( any points/guidelines) one could use for going about Implementation( in the form of Implementation Details) in Python and C++ . Although this might sound specific as the query is "Implementation Details" and is different for different cases as one goes about the REAL implementation, I just want a SET of guidelines one should follow ( Preferably In Python, C++ specific, even for any other language is Welcome) if this( Implementation Details ) has to also be documented or presented. Hope the question is clear, I am sorry if it still sounds ambiguous, I guess this is the best I could do to frame my query. Thank you for your time...:)

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  • Best programming language for a beginner to learn?

    - by Dean
    I am teaching my friend how to program in C, he has no programming experience. He wants to learn C so that he can program different microprocessors. I have suggested he learn another language something like java or ruby so that he can learn basics before moving on to a language like C. Is this advisable or should i just teach him C?

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  • Stepping into Ruby Meta-Programming: Generating proxy methods for multiple internal methods

    - by mstksg
    Hi all; I've multiply heard Ruby touted for its super spectacular meta-programming capabilities, and I was wondering if anyone could help me get started with this problem. I have a class that works as an "archive" of sorts, with internal methods that process and output data based on an input. However, the items in the archive in the class itself are represented and processed with integers, for performance purposes. The actual items outside of the archive are known by their string representation, which is simply number_representation.to_s(36). Because of this, I have hooked up each internal method with a "proxy method" that converts the input into the integer form that the archive recognizes, runs the internal method, and converts the output (either a single other item, or a collection of them) back into strings. The naming convention is this: internal methods are represented by _method_name; their corresponding proxy method is represented by method_name, with no leading underscore. For example: class Archive ## PROXY METHODS ## ## input: string representation of id's ## output: string representation of id's def do_something_with id result = _do_something_with id.to_i(36) return nil if result == nil return result.to_s(36) end def do_something_with_pair id_1,id_2 result = _do_something_with_pair id_1.to_i(36), id_2.to_i(36) return nil if result == nil return result.to_s(36) end def do_something_with_these ids result = _do_something_with_these ids.map { |n| n.to_i(36) } return nil if result == nil return result.to_s(36) end def get_many_from id result = _get_many_from id return nil if result == nil # no sparse arrays returned return result.map { |n| n.to_s(36) } end ## INTERNAL METHODS ## ## input: integer representation of id's ## output: integer representation of id's def _do_something_with id # does something with one integer-represented id, # returning an id represented as an integer end def do_something_with_pair id_1,id_2 # does something with two integer-represented id's, # returning an id represented as an integer end def _do_something_with_these ids # does something with multiple integer ids, # returning an id represented as an integer end def _get_many_from id # does something with one integer-represented id, # returns a collection of id's represented as integers end end There are a couple of reasons why I can't just convert them if id.class == String at the beginning of the internal methods: These internal methods are somewhat computationally-intensive recursive functions, and I don't want the overhead of checking multiple times at every step There is no way, without adding an extra parameter, to tell whether or not to re-convert at the end I want to think of this as an exercise in understanding ruby meta-programming Does anyone have any ideas? edit The solution I'd like would preferably be able to take an array of method names @@PROXY_METHODS = [:do_something_with, :do_something_with_pair, :do_something_with_these, :get_many_from] iterate through them, and in each iteration, put out the proxy method. I'm not sure what would be done with the arguments, but is there a way to test for arguments of a method? If not, then simple duck typing/analogous concept would do as well.

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  • Generic Lists copying references rather than creating a copiedList

    - by Dean
    I was developing a small function when trying to run an enumerator across a list and then carry out some action. (Below is an idea of what I was trying to do. When trying to remove I got a "Collection cannot be modified" which after I had actually woken up I realised that tempList must have just been assigned myLists reference rather than a copy of myLists. After that I tried to find a way to say tempList = myList.copy However nothing seems to exist?? I ended up writing a small for loop that then just added each item from myLsit into tempList but I would have thought there would have been another mechanism (like clone??) So my question(s): is my assumption about tempList receiving a reference to myList correct How should a list be copied to another list? private myList as List (Of something) sub new() myList.add(new Something) end sub sub myCalledFunction() dim tempList as new List (Of Something) tempList = myList Using i as IEnumerator = myList.getEnumarator while i.moveNext 'if some critria is met then tempList.remove(i.current) end end using end sub

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  • Creating a Type object corresponding to a generic type

    - by Alexey Romanov
    In Java, how can I construct a Type object for Map<String, String>? System.out.println(Map<String, String>.class); doesn't compile. One workaround I can think of is private Map<String, String> dummy() { throw new Error(); } Type mapStringString = Class.forName("ThisClass").getMethod("dummy", null).getGenericReturnType(); Is this the correct way?

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  • .NET XmlSerializer fails with List<T>

    - by Redshirt
    I'm using a singleton class to save all my settings info. It's first utilized by calling Settings.ValidateSettings(@"C:\MyApp"). The problem I'm having is that 'List Contacts' is causing the xmlserializer to fail to write the settings file, or to load said settings. If I comment out the List<T> then I have no problems saving/loading the xml file. What am I doing wrong? // The actual settings to save public class MyAppSettings { public bool FirstLoad { get; set; } public string VehicleFolderName { get; set; } public string ContactFolderName { get; set; } public List<ContactInfo> Contacts { get { if (contacts == null) contacts = new List<ContactInfo>(); return contacts; } set { contacts = value; } } private List<ContactInfo> contacts; } // The class in which the settings are manipulated public static class Settings { public static string SettingPath; private static MyAppSettings instance; public static MyAppSettings Instance { get { if (instance == null) instance = new MyAppSettings(); return instance; } set { instance = value; } } public static void InitializeSettings(string path) { SettingPath = Path.GetFullPath(path + "\\MyApp.xml"); if (File.Exists(SettingPath)) { LoadSettings(); } else { Instance.FirstLoad = true; Instance.VehicleFolderName = "Cars"; Instance.ContactFolderName = "Contacts"; SaveSettingsFile(); } } // load the settings from the xml file private static void LoadSettings() { XmlSerializer ser = new XmlSerializer(typeof(MyAppSettings)); TextReader reader = new StreamReader(SettingPath); Instance = (MyAppSettings)ser.Deserialize(reader); reader.Close(); } // Save the settings to the xml file public static void SaveSettingsFile() { XmlSerializer ser = new XmlSerializer(typeof(MyAppSettings)); TextWriter writer = new StreamWriter(SettingPath); ser.Serialize(writer, Settings.Instance); writer.Close(); } public static bool ValidateSettings(string initialFolder) { try { Settings.InitializeSettings(initialFolder); } catch (Exception e) { return false; } // Do some validation logic here return true; } } // A utility class to contain each contact detail public class ContactInfo { public string ContactID; public string Name; public string PhoneNumber; public string Details; public bool Active; public int SortOrder; }

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  • Diminishing programmer wants to get back to programming

    - by Marcus TV
    I last programmed actively in 2002. It is almost 8 years now. I learned C and then moved to Visual Basic for our thesis project in the university. I would like to ask suggestions on what programming language should I learn and put to profitability use in areas such as desktop applications, web development, and database applications.

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  • c# Reflection - Find the Generic Type of a Collection

    - by Andy Clarke
    Hi, I'm reflecting a property 'Blah' its Type is ICollection public ICollection<string> Blah { get; set; } private void button1_Click(object sender, RoutedEventArgs e) { var pi = GetType().GetProperty("Blah"); MessageBox.Show(pi.PropertyType.ToString()); } This gives me (as you'd expect!) ICollection<string> ... But really I want to get the collection type i.e. ICollection (rather than ICollection<string>) - does anyone know how i'd do this please?

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  • Exporting data to an accounting system for billing and invoicing - is there any generic standard pra

    - by Ali
    Hi guys, I've built a web application which basically logs work that has been done upon projects plus maintain resources used etc. What I need now is to set it up so that projects can be billed. Billed such that - each task that has been undertaken in a project is regarded as a billable service. Instead of building my own invoicing system and accounts management system I was wondering if there was any standard data format i.e in xml DTD or so to which I could set up the information so it could be imported by a third party accounting system for billing - or if not then what is the best way to accomplish this. I need to integrate invoicing capabilities somehow - better if its third party as I don't wish to have to go through building an entire accounting system.

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