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  • Generic Func<> as parameter to base method

    - by WestDiscGolf
    I might be losing the plot, but I hope someone can point me in the right direction. What am I trying to do? I'm trying to write some base methods which take Func< and Action so that these methods handle all of the exception handling etc. so its not repeated all over the place but allow the derived classes to specify what actions it wants to execute. So far this is the base class. public abstract class ServiceBase<T> { protected T Settings { get; set; } protected ServiceBase(T setting) { Settings = setting; } public void ExecAction(Action action) { try { action(); } catch (Exception exception) { throw new Exception(exception.Message); } } public TResult ExecFunc<T1, T2, T3, TResult>(Func<T1, T2, T3, TResult> function) { try { /* what goes here?! */ } catch (Exception exception) { throw new Exception(exception.Message); } } } I want to execute an Action in the following way in the derived class (this seems to work): public void Delete(string application, string key) { ExecAction(() => Settings.Delete(application, key)); } And I want to execute a Func in a similar way in the derived class but for the life of me I can't seem to workout what to put in the base class. I want to be able to call it in the following way (if possible): public object Get(string application, string key, int? expiration) { return ExecFunc(() => Settings.Get(application, key, expiration)); } Am I thinking too crazy or is this possible? Thanks in advance for all the help.

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  • c# ProcessCmdKey overload, match generic combination

    - by leo
    Hi all, On some control, I want ProcessCmdKey to return true if the keys pressed by the user were ALT and any letter of the alphabet. I'm able to return true if the user presses Alt with the following code, but how can I add the condition of a letter also pressed ? protected override bool ProcessCmdKey(ref Message msg, Keys keyData) { if ((keyData & Keys.Alt) != 0) { return true; } } Thanks.

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  • Invoking static methods containing Generic Parameters using Reflection.

    - by AJP
    While executing the following code i gets this error "Late bound operations cannot be performed on types or methods for which ContainsGenericParameters is true." class Program { static void Main(string[] args) { MethodInfo MI = typeof(MyClass).GetMethod("TestProc"); MI.MakeGenericMethod(new [] {typeof(string)}); MI.Invoke(null, new [] {"Hello"}); } } class MyClass { public static void TestProc<T>(T prefix) { Console.WriteLine("Hello"); } } Please help.

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  • How to manage a BorderLayout with generic JPanel()

    - by Nick G.
    Im not sure how to reference to JPanel when it was declared like this, I had someone else help me on JPanels and this is the code he used: final JFrame frame = new JFrame("CIT Test Program"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setPreferredSize(new Dimension(350, 250)); frame.add(new JPanel() {{ Not sure how to reference to JPanel to use BorderLayout. How would I go about doing this?

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  • C#, Using Custom Generic Collection faster with objects than List

    - by Kaminari
    Hello, I'm using for now List< to iterate through some object collection and find matching element, The problem is that object has only 2 significant values Name and Link (strings) but has some other values wich I dont want to compare. I'm thinkig about using something like HashSet (wich is exactly what I'm searching for - fast) from .NET 3.5 but target framework has to be 2.0. There is something called Power Collections here: http://powercollections.codeplex.com/ But maybe there is other way? If not, can you suggest me a suitable custom collection?

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  • Comparing the values of two generic Numbers

    - by PartlyCloudy
    I want to compare to variables, both of type T extends Number. Now I want to know which of the two variables is greater than the other or equal. Unfortunately I don't know the exact type yet, I only know that it will be a subtype of java.lang.Number. How can I do that? Thanks!

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  • Why isn't the new() generic constraint satisfied by a class with optional parameters in the construc

    - by Joshua Flanagan
    The following code fails to compile, producing a "Widget must be a non-abstract type with a public parameterless constructor" error. I would think that the compiler has all of the information it needs. Is this a bug? An oversight? Or is there some scenario where this would not be valid? public class Factory<T> where T : new() { public T Build() { return new T(); } } public class Widget { public Widget(string name = "foo") { Name = name; } public string Name { get; set; } } public class Program { public static void Main() { var widget = new Widget(); // this is valid var factory = new Factory<Widget>(); // compiler error } }

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  • C# Possible to have a generic return type?

    - by JL
    Here is a typical function that returns either true/false; private static bool hasValue() { return true; } Now on an error, I would like to return my own custom error object with definition: public class Failure { public string failureDateTime { get; set; } public string failureReason { get; set; } } I would have expected to be able to throw this custom object for example... private static bool hasValue() { throw new Failure(); } This is not possible, and I don't want to derive Failure from System.IO.Exception because of the inability to serialize an exception in C#. What is the best practice / or ideal solution to this problem. Should I just work with private static object? Or is there a cleaner way to return a custom object or bypass the typical return type on an error (not using System.IO.Exception)? Not entirely wild about object either, because then I need to cast the result and validate it by more boolean logic.

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  • A strange error in java generic.

    - by ???
    This is ok: Class<? extends String> stringClass = "a".getClass(); But this gets error: <T> void f(T obj) { Class<? extends T> objClass = obj.getClass(); } I know I can cast it like: <T> void f(T obj) { @SuppressWarnings("unchecked") Class<? extends T> objClass = (Class<? extends T>) obj.getClass(); } But why the previous error? Will the next release of Java 7 will support such usage?

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  • Overriding inherited generic methods

    - by jess
    I have this code in base class protected virtual bool HasAnyStuff<TObject>(TObject obj) where TObject:class { return false; } In child class I am overriding protected override bool HasAnyStuff<Customer>(Customer obj) { //some stuff if Customer.sth etc return false; } I am getting this error '''Type parameter declaration must be an identifier not a type''' What is it I am doing wrong here?

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  • Generic DRM (Distributed resource management) wrapper

    - by Pavel Bernshtam
    I need to write a software, which launches DRM jobs in a customer environment and monitors those jobs status. It should work with various customer environments and DRMs - like LSF, Sun Grid and others. Can you recommend some 3rd party library, which hides DRM differences from me and has API like "launch job", "get list of jobs", "get job status" etc. ? Both Java and native libraries are good for me.

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  • C# determining generic type

    - by Chris Klepeis
    I have several templated objects that all implement the same interface: I.E. MyObject<datatype1> obj1; MyObject<datatype2> obj2; MyObject<datatype3> obj3; I want to store these objects in a List... I think I would do that like this: private List<MyObject<object>> _myList; I then want to create a function that takes 1 parameter, being a datatype, to see if an object using that datatype exists in my list.... sorta clueless how to go about this. In Pseudo code it would be: public bool Exist(DataType T) { return (does _myList contain a MyObject<T>?); }

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  • How to create a generic Android XML layout for all activities

    - by zabawaba
    I have an application that needs the same items [5 buttons acting as tabs] in every screen. Is it possible to create a "base XML layout" that has these 5 buttons and then have all the other XML files extend from the bas layout in some way so that I don't have to have multiple buttons that will ultimately have the same functionality. Is there a better approach to this problem that can be supported by API 9

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  • Generic collection class?

    - by Mark
    Is there anyway I can do this? class TSOC<TCollection, TValue> : ICollection<TValue>, INotifyCollectionChanged where TCollection : ICollection { private TCollection<TValue> collection; } It doesn't like my definition of collection. I'd prefer the definition to look like TSOC<TCollection> where the user can pass in List<int> or something, but then I need to pull out the "int" to know what interface to implement.

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  • How online-game clients are able to exchange data through internet so fast?

    - by Kirzilla
    Hello, Let's imagine really simple game... We have a labirinth and two players trying to find out exit in real time through internet. On every move game client should send player's coordinates to server and accept current coordinates of another client. How is it possible to make this exchange so fast (as all modern games do). Ok, we can use memcache or similar technology to reduce data mining operations on server side. We can also use fastest webserver etc., but we still will have problems with timings. So, the questions are... What protocol game clients are usually using for exchanging information with server? What server technologies are coming to solve this problem? What algorithms are applied for fighting with delays during game etc. PS: Sorry for my English and I hope that my question is clear. Thank you.

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  • How Can I Accept a Generic Class and Use Its Properties / Methods

    - by Blake Blackwell
    I want to create a class that could hold any of a number of same type of classes. For example lets says I have a base class like follows: public class BaseClass { public string MyBaseString { get; set; } } And then I have a few derived classes like this: public class DerivedClass : BaseClass { public MyDerivedClassString { get; set; } } public class DerivedClass2 : BaseClass { public MyDerivedClass2String { get; set; } } Now I would like a class that accepts one of these implementations and does stuff with it. Here is the only thing I can think of, but there must be a better way: public class ClassA { public object MyClass { get; set; } public ClassA (object myClass) { MyClass = myClass; if (object is BaseClass) { //do something } else if (object is DerivedClass) { //do something specific to derived class } else if (object is DerivedClass2) { //do something specific to derived class 2 } } } I'm not sure really what I'm looking for here. Any ideas would be great!

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  • Passing a generic class to a java function?

    - by rodo
    Is it possible to use Generics when passing a class to a java function? I was hoping to do something like this: public static class DoStuff { public <T extends Class<List>> void doStuffToList(T className) { System.out.println(className); } public void test() { doStuffToList(List.class); // compiles doStuffToList(ArrayList.class); // compiler error (undesired behaviour) doStuffToList(Integer.class); // compiler error (desired behaviour) } } Ideally the List.class and ArrayList.class lines would work fine, but the Integer.class line would cause a compile error. I could use Class as my type instead of T extends Class<List> but then I won't catch the Integer.class case above.

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  • implict type cast in generic method

    - by bitbonk
    why do I get a compiler error in the following code stating: Cannot implicty convert type SpecialNode to T even though T must derive from NodeBase as I defined in the where clause and even though SpecialNode actually derived from NodeBase? public static T GetNode<T>() where T : NodeBase { if (typeof(T) == typeof(SpecialNode)) { return ThisStaticClass.MySpecialNode; // <-- compiler error } if (typeof(T) == typeof(OtherSpecialNode)) { return ThisStaticClass.MyOtherSpecialNode; // <-- compiler error } ... return default(T); }

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  • Dispatching generic tasks in WCF or .Net Remoting

    - by Eric
    Hello all, I've been researching for a couple days on and off, and have yet to figure out the best way to achieve the following goal. I would like to define either an interface or abstract class in C# which has an associated Run method, similar to the Java runnable interface. The goal would be to have a shared queue which contains a list of these objects. Then individual clients would be able to derive their own concrete runnable classes and add them to the queue hosted by the server. Clients would also be able to pop these runnable objects off the queue and execute them arbitrarily. This seems like it should be feasible in a VM based language without needing to place any of the concrete implementations in a shared assembly, but I have thus far had no luck finding a working example of such a system. Does anyone know how this might be achieved?

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  • Linq based generic alternate to Predicate<T>?

    - by Eric
    I have an interface called ICatalog as shown below where each ICatalog has a name and a method that will return items based on a Predicate<Item> function. public interface ICatalog { string Name { get; } IEnumerable<IFamily> GetItems(Predicate<Item> predicate); } A specific implementation of a catalog may be linked to catalogs in various format such as XML, or a SQL database. With an XML catalog I end up deserializing the entire XML file into memory, so testing each item with the predicate function does does not add a whole lot more overhead as it's already in memory. Yet with the SQL implementation I'd rather not retrieve the entire contents of the database into memory, and then filter the items with the predicate function. Instead I'd want to find a way to somehow pass the predicate to the SQL server, or somehow convert it to a SQL query. This seems like a problem that can be solved with Linq, but I'm pretty new to it. Should my interface return IQueryable instead?

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  • How to inherit from a generic parameter?

    - by Bob
    I'm basically wanting to do this: class UILockable<T> : T where T : UIWidget { } However, this doesn't work. I've seen people recommend that you do this: class UILockable<T> where T : UIWidget { private T _base; } This would require me to override each function UILockable would need and forward it to T. This is impossible since T may derive from UIWidget and have unique abstract/virtual methods of its own. Is there no way to simply inherit from T?

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  • C# Generic Collection help

    - by dcmovva
    I have a requirement to implement some kind of dictionary object. Something like MyDict<K,V1, V2). For example if I have a Question as Key(k) then Correct answer is V1 . V2 is user selected answer. Is there a collection that would satisfy this requirement in C#. If I have to design my own type, what interfaces should I implement. ICollection and Ilist ?

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  • can I get .class from generic type argument?

    - by Mike S
    I have the following class: public abstract class MyClass<T extends Object> { protected T createNewFromData(Reader reader){ GSON.fromJSON(reader,T.class); // T.class isn't allowed :( } } How do I pass a Class<T instance into there? Is there some wierd and wacky work around? Is there a way to get a Class<T reference other than from a pre-instantiated Object of type T? It won't let me do this either: T t = new T(); Class<T> klass = t.class; ANSWER BELOW Thanks to the accepted answer, here is the solution: Type type = new TypeToken<T>(){}.getType(); return gson.fromJson(reader, type);

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