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  • Bind postback data from a strong type view of type List<T>

    - by Robert Koritnik
    I have a strong type view of type List<List<MyViewModelClass>> The outer list will always have two lists of List<MyViewModelClass>. For each of the two outer lists I want to display a group of checkboxes. Each set can have an arbitrary number of choices. My view model class looks similar to this: public class MyViewModelClass { public Area Area { get; set; } public bool IsGeneric { get; set; } public string Code { get; set; } public bool IsChecked { get; set; } } So the final view will look something like: Please select those that apply: First set of choices: x Option 1 x Option 2 x Option 3 etc. Second set of choices: x Second Option 1 x Second Option 2 x Second Option 3 x Second Option 4 etc. Checkboxes should display MyViewModelClass.Area.Name, and their value should be related to MyViewModelClass.Area.Id. Checked state is of course related to MyViewModel.IsChecked. Question I wonder how should I use Html.CheckBox() or Html.CheckBoxFor() helper to display my checkboxes? I have to get these values back to the server on a postback of course. I would like to have my controller action like one of these: public ActionResult ConsumeSelections(List<List<MyViewModelClass>> data) { // process data } public ActionResult ConsumeSelections(List<MyViewModelClass> first, List<MyViewModelClass> second) { // process data } If it makes things simpler, I could make a separate view model type like: public class Options { public List First { get; set; } public List Second { get; set; } } As well as changing my first version of controller action to: public ActionResult ConsumeSelections(Options data) { // process data }

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  • Java Generic Casting Type Mismatch

    - by Kay
    public class MaxHeap<T extends Comparable<T>> implements Heap<T>{ private T[] heap; private int lastIndex; public void main(String[] args){ int i; T[] arr = {1,3,4,5,2}; //ERROR HERE ******* foo } public T[] Heapsort(T[]anArray, int n){ // build initial heap T[]sortedArray = anArray; for (int i = n-1; i< 0; i--){ //assert: the tree rooted at index is a semiheap heapRebuild(anArray, i, n); //assert: the tree rooted at index is a heap } //sort the heap array int last = n-1; //invariant: Array[0..last] is a heap, //Array[last+1..n-1] is sorted for (int j=1; j<n-1;j++) { sortedArray[0]=sortedArray[last]; last--; heapRebuild(anArray, 0, last); } return sortedArray; } protected void heapRebuild(T[ ] items, int root, int size){ foo } } The error is on the line with "T[arr] = {1,3,4,5,2}" Eclispe complains that there is a: "Type mismatch: cannot convert from int to T" I've tried to casting nearly everywhere but to no avail.A simple way out would be to not use generics but instead just ints but that's sadly not an option. I've got to find a way to resolve the array of ints "{1,3,4,5,2}" into an array of T so that the rest of my code will work smoothly.

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  • Abstract Factory Using Generics: Is Explicitly Converting a Specified Type to Generic a Bad Practice

    - by Merritt
    The question's title says it all. I like how it fits into the rest of my code, but does it smell? public interface IFoo<T> { T Bar { get; set; } } public class StringFoo : IFoo<string> { public string Bar { get; set; } } public static class FooFactory { public static IFoo<T> CreateFoo<T>() { if (typeof(T) == typeof(string)) { return new StringFoo() as IFoo<T>; } throw new NotImplementedException(); } } UPDATE: this is sort of a duplicate of Is the StaticFactory in codecampserver a well known pattern?

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  • In VB.NET how do you specify Inherits/implements on a generic class with multi-constraints

    - by Romel Evans
    When I write the following statement in VB.Net (C# is my normal language), I get an "end of statement expected" referring to the "Implements" statement. <Serializable()> _ <XmlSchemaProvider("EtgSchema")> _ Public Class SerializeableEntity(Of T As {Class, ISerializable, New}) _ Implements IXmlSerializable, ISerializable ... End Class The C# version that I'm trying to emulate is: [Serializable] [XmlSchemaProvider("MySchema")] public class SerializableEntity<T> : IXmlSerializable, ISerializable where T : class, new() { .... } Sometimes I feel like I have 5 thumbs with VB.NET :)

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  • Access generic type parameter at runtime?

    - by Bart van Heukelom
    Event dispatcher interface public interface EventDispatcher { <T> EventListener<T> addEventListener(EventListener<T> l); <T> void removeEventListener(EventListener<T> l); } Implementation public class DefaultEventDispatcher implements EventDispatcher { @SuppressWarnings("unchecked") private Map<Class, Set<EventListener>> listeners = new HashMap<Class, Set<EventListener>>(); public void addSupportedEvent(Class eventType) { listeners.put(eventType, new HashSet<EventListener>()); } @Override public <T> EventListener<T> addEventListener(EventListener<T> l) { Set<EventListener> lsts = listeners.get(T); // ****** error: cannot resolve T if (lsts == null) throw new RuntimeException("Unsupported event type"); if (!lsts.add(l)) throw new RuntimeException("Listener already added"); return l; } @Override public <T> void removeEventListener(EventListener<T> l) { Set<EventListener> lsts = listeners.get(T); // ************* same error if (lsts == null) throw new RuntimeException("Unsupported event type"); if (!lsts.remove(l)) throw new RuntimeException("Listener is not here"); } } Usage EventListener<ShapeAddEvent> l = addEventListener(new EventListener<ShapeAddEvent>() { @Override public void onEvent(ShapeAddEvent event) { // TODO Auto-generated method stub } }); removeEventListener(l); I've marked two errors with a comment above (in the implementation). Is there any way to get runtime access to this information?

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  • Cloned Cached item has memory issues

    - by ioWint
    Hi there, we are having values stored in Cache-Enterprise library Caching Block. The accessors of the cached item, which is a List, modify the values. We didnt want the Cached Items to get affected. Hence first we returned a new List(IEnumerator of the CachedItem) This made sure accessors adding and removing items had little effect on the original Cached item. But we found, all the instances of the List we returned to accessors were ALIVE! Object relational Graph showed a relationship between this list and the EnterpriseLibrary.CacheItem. So we changed the return to be a newly cloned List. For this we used a LINQ say (from item in Data select new DataClass(item) ).ToList() even when you do as above, the ORG shows there is a relationship between this list and the CacheItem. Cant we do anything to create a CLONE of the List item which is present in the Enterprise library cache, which DOESNT have ANY relationship with CACHE?!

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  • ASP.NET MVC PartialView generic ModelView

    - by Greg Ogle
    I have an ASP.NET MVC application which I want to dynamically pick the partial view and what data gets passed to it, while maintaining strong types. So, in the main form, I want a class that has a view model that contains a generically typed property which should contain the data for the partial view's view model. public class MainViewModel<T> { public T PartialViewsViewModel { get; set; } } In the User Control, I would like something like: Inherits="System.Web.Mvc.ViewUserControl<MainViewModel<ParticularViewModel>>" %> Though in my parent form, I must put Inherits="System.Web.Mvc.ViewPage<MainViewModel<ParticularViewModel>>" %> for it to work. Is there a way to work around this? The use case is to make the user control pluggable. I understand that I could inherit a base class, but that would put me back to having something like a dictionary instead of a typed view model.

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  • Best way to translate from IDictionary to a generic IDictionary

    - by George Mauer
    I've got an IDictionary field that I would like to expose via a property of type IDictionary<string, dynamic> the conversion is surprisingly difficult since I have no idea what I can .Cast<>() the IDictionary to. Best I've got: IDictionary properties; protected virtual IDictionary<string, dynamic> Properties { get { return _properties.Keys.Cast<string>() .ToDictionary(name=>name, name=> _properties[name] as dynamic); } }

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  • Function-Local Static Const variable Initialization semantics.

    - by Hassan Syed
    The questions are in bold, for those that cannot be bothered reading a question in depth. This is a followup to this question. It is to do with the initialization semantics of static variables in functions. Static variables should be initialized once, and their internal state might be altered later - as I (currently) do in the linked question. However, the code in question does not require the feature to change the state of the variable later. Let me clarrify my position, since I don't require the string object's internal state to change. The code is for a trait class for meta programming, and as such would would benifit from a const char * const ptr -- thus Ideally a local cost static const variable is needed. My educated guess is that in this case the string in question will be optimally placed in memory by the link-loader, and that the code is more secure and maps to the intended semantics. This leads to the semantics of such a variable "The C++ Programming language Third Edition -- Stroustrup" does not have anything (that I could find) to say about this matter. All that is said is that the variable is initialized once when the flow of control of the thread first reaches the code. This leads me to ponder if the following code would be sensible, and if not what are the intended semantics ?. #include <iostream> const char * const GetString(const char * x_in) { static const char * const x = x_in; return x; } int main() { const char * const temp = GetString("yahoo"); std::cout << temp << std::endl; const char * const temp2 = GetString("yahoo2"); std::cout << temp2 << std::endl; } The following compiles on GCC and prints "yahoo" twice. Which is what I want -- However it might not be standards compliant (which is why I post this question). It might be more elegant to have two functions, "SetString" and "String" where the latter forwards to the first. If it is standards compliant does someone know of a templates implementation in boost (or elsewhere) ?

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  • How can i use generic list with foreach?

    - by Phsika
    if i compiled below codes error return foreach loop how can i solve it? Error:Error 1 foreach statement cannot operate on variables of type 'Sortlist.MyCalisan' because 'Sortlist.MyCalisan' does not contain a public definition for 'GetEnumerator' C:\Users\yusuf.karatoprak\Desktop\ExcelToSql\TestExceltoSql\Sortlist\Program.cs 46 13 Sortlist static void EskiMetodlaListele() { MyCalisan myCalisan = new MyCalisan(); Calisan calisan = new Calisan(); calisan.Ad = "ali"; calisan.SoyAd = "abdullah"; calisan.ID = 1; myCalisan.list.Add(calisan); foreach (Calisan item in myCalisan) { Console.WriteLine(item.Ad.ToString()); } } } public class Calisan { public int ID { get; set; } public string Ad { get; set; } public string SoyAd { get; set; } } public class MyCalisan { public List<Calisan> list { get; set; } public MyCalisan() { list = new List(); } }

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  • Cascading IEquatable(Of T)

    - by Shimmy
    Hello! I have several entities I need to make IEquatable(Of TEntity) respectively. I want them first to check equality between EntityId, then if both are zero, should check regarding to other properties, for example same contact names, same phone number etc. How is this done?

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  • Type-safe, generic, empty Collections with static generics

    - by Droo
    I return empty collections vs. null whenever possible. I switch between two methods for doing so using java.util.Collections: return Collections.EMPTY_LIST; return Collections.emptyList(); where emptyList() is supposed to be type-safe. But I recently discovered: return Collections.<ComplexObject> emptyList(); return Collections.<ComplexObject> singletonList(new ComplexObject()); etc. I see this method in Eclipse Package Explorer: <clinit> () : void but I don't see how this is done in the source code (1.5). How is this magic tomfoolerie happening!!

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  • Ambiguous Generic restriction T:class vs T:struct

    - by Maslow
    This code generates a compiler error that the member is already defined with the same parameter types. private T GetProperty<T>(Func<Settings, T> GetFunc) where T:class { try { return GetFunc(Properties.Settings.Default); } catch (Exception exception) { SettingReadException(this,exception); return null; } } private TNullable? GetProperty<TNullable>(Func<Settings, TNullable> GetFunc) where TNullable : struct { try { return GetFunc(Properties.Settings.Default); } catch (Exception ex) { SettingReadException(this, ex); return new Nullable<TNullable>(); } } Is there a clean work around?

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  • Convert a generic list to an array

    - by Freewind
    I have searched for this, but unfortunately, I don't get the correct answer. class Helper { public static <T> T[] toArray(List<T> list) { T[] array = (T[]) new Object[list.size()]; for (int i = 0; i < list.size(); i++) { array[i] = list.get(i); } return array; } } Test it: public static void main(String[] args) { List<String> list = new ArrayList<String>(); list.add("abc"); String[] array = toArray(list); System.out.println(array); } But there is an error thrown: Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.String; at test.Helper.main(Helper.java:30) How to solve this?

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  • Converting a list of an Structure into datatable

    - by strakastroukas
    I saw a lot of examples regarding conversion of a list to data-table. I would like to convert a list of structure into a data-table. How can i do that? My structure is like ... Structure MainStruct Dim Ans1 As String Dim Ans2 As String Dim Ans3 As String Dim Skipped As Boolean End Structure and... Dim St As New MainStruct Dim Build As New List(Of MainStruct) I would like to convert the Build to a datatable

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  • Help Modifying Generic REST Helper PHP Example Code to Support XML DOM

    - by Jennifer Baker
    Hi! I found this example PHP source code at HTTP POST from PHP, without cURL I need some help modifying the example PHP source to support XML DOM for manipulating a REST API. I thought that if I update the CASE statement for the XML section below from $r = simplexml_load_string($res); to $r = new DOMDocument(); $r->load($res); that it would work but it doesn't. :( Any help would be appreciated. function rest_helper($url, $params = null, $verb = 'GET', $format = 'xml') { $cparams = array( 'http' => array( 'method' => $verb, 'ignore_errors' => true ) ); if ($params !== null) { $params = http_build_query($params); if ($verb == 'POST') { $cparams['http']['content'] = $params; } else { $url .= '?' . $params; } } $context = stream_context_create($cparams); $fp = fopen($url, 'rb', false, $context); if (!$fp) { $res = false; } else { // If you're trying to troubleshoot problems, try uncommenting the // next two lines; it will show you the HTTP response headers across // all the redirects: // $meta = stream_get_meta_data($fp); // var_dump($meta['wrapper_data']); $res = stream_get_contents($fp); } if ($res === false) { throw new Exception("$verb $url failed: $php_errormsg"); } switch ($format) { case 'json': $r = json_decode($res); if ($r === null) { throw new Exception("failed to decode $res as json"); } return $r; case 'xml': $r = simplexml_load_string($res); if ($r === null) { throw new Exception("failed to decode $res as xml"); } return $r; } return $res; }

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  • Calling a method with an instance of derived class of derived generic type

    - by madsbirk
    Okay, so I have classes class B<T> : A<T> class L : K and a method void Method(A<K> a) {...} What I would like to do is this b = new B<L>(); Method(b); //error But it is not possible to b to the correct type. Indeed it is not possible to make this cast A<K> t = new A<L>(); //error I would really like to not have to change the internals of Method. I have no problems making changes to B and/or L. Do I have any options for making some sort of workaround? I guess it should be possible for Method to execute all of its method calls etc. on b, since B derives from A and L derives from K?

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  • Using Accelerometer in Wiimote for Physics Practicals

    - by Omar
    I have to develop some software in my school to utilize the accelerometer in the Wiimote for recording data from experiments, for example finding the acceleration and velocity of a moving object. I understand how the accelerometer values will be used but I am sort of stuck on the programming front. There is a set of things that I would like to do: Live streaming of data from the Wiimote via bluetooth Use the accelerometer values to find velocity and displacment via integration Plot a set of results Avoid the use of the infrared sensor on the Wiimote Please can anyone give me their thoughts on how to go about this. Also it would be great if people could direct me to existing projects that utizlise the wiimote. Also can someone suggest what would be the best programming language to use for this. My current bet is on using Visual basic. Any sort of help is greatly appretiated.

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  • Is there a way to make ToEnum generic

    - by maxfridbe
    I would like to do this but it does not work. bool TryGetEnum<TEnum, TValue>(TValue value, out TEnum myEnum) { if (Enum.IsDefined(typeof(TEnum), value)) { myEnum = (TEnum)value; return true; } return false; } Example usage: MyEnum mye; bool success = this.TryGetEnum<MyEnum,char>('c',out mye);

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  • How to call notifyDataSetChanged() from a generic Adapter

    - by Matty F
    An OnItemClickListener for a ListView has the following method: @Override public void onItemClick(AdapterView<?> parent, View v, int position, long id) I'd like to have the adapter behind the ListView refresh, and I believe this is done through the use of: BaseAdapter.notifyDataSetChanged() How do I use the parent parameter in the onItemClick method to do this? So far I've tried: parent.getAdapter().notifyDataSetChanged(); This throws an error because the object returned is of class HeaderViewListAdapter, which for reasons unknown isn't a subclass of BaseAdapter.

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  • How to Create a Generic Method and Create Instance of The Type

    - by DaveDev
    Hi Guys I want to create a helper method that I can imagine has a signature similar to this: public static MyHtmlTag GenerateTag<T>(this HtmlHelper htmlHelper, object obj) { // how do I create an instance of MyAnchor? // this returns MyAnchor, which has a MyHtmlTag base } When I invoke the method, I want to specify a type of MyHtmlTag, such as MyAnchor, e.g.: <%= Html.GenerateTag<MyAnchor>(obj) %> or <%= Html.GenerateTag<MySpan>(obj) %> Can someone show me how to create this method? Also, what's involved in creating an instance of the type I specified? Activator.CreateInstance()? Thanks Dave

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  • Modeling a Generic Relationship (expressed in C#) in a Database

    - by StevenH
    This is most likely one for all you sexy DBAs out there: How would I effieciently model a relational database whereby I have a field in an "Event" table which defines a "SportType"? This "SportsType" field can hold a link to different sports tables E.g. "FootballEvent", "RubgyEvent", "CricketEvent" and "F1 Event". Each of these Sports tables have different fields specific to that sport. My goal is to be able to genericly add sports types in the future as required, yet hold sport specific event data (fields) as part of my Event Entity. Is it possible to use an ORM such as NHibernate / Entity framework / DataObjects.NET which would reflect such a relationship? I have thrown together a quick C# example to express my intent at a higher level: public class Event<T> where T : new() { public T Fields { get; set; } public Event() { EventType = new T(); } } public class FootballEvent { public Team CompetitorA { get; set; } public Team CompetitorB { get; set; } } public class TennisEvent { public Player CompetitorA { get; set; } public Player CompetitorB { get; set; } } public class F1RacingEvent { public List<Player> Drivers { get; set; } public List<Team> Teams { get; set; } } public class Team { public IEnumerable<Player> Squad { get; set; } } public class Player { public string Name { get; set; } public DateTime DOB { get; set;} }

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