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  • Unchecked call to compareTo

    - by Dave Jarvis
    Background Create a Map that can be sorted by value. Problem The code executes as expected, but does not compile cleanly: http://pastebin.com/bWhbHQmT The syntax for passing Comparable as a generic parameter along to the Map.Entry<K, V> (where V must be Comparable?) -- so that the (Comparable) typecast shown in the warning can be dropped -- eludes me. Warning Compiler's cantankerous complaint: SortableValueMap.java:24: warning: [unchecked] unchecked call to compareTo(T) as a member of the raw type java.lang.Comparable return ((Comparable)entry1.getValue()).compareTo( entry2.getValue() ); Question How can the code be changed to compile without any warnings (without suppressing them while compiling with -Xlint:unchecked)? Related TreeMap sort by value How to sort a Map on the values in Java? http://paaloliver.wordpress.com/2006/01/24/sorting-maps-in-java/ Thank you!

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  • How can i convert this to a factory/abstract factory?

    - by Amitd
    I'm using MigraDoc to create a pdf document. I have business entities similar to the those used in MigraDoc. public class Page{ public List<PageContent> Content { get; set; } } public abstract class PageContent { public int Width { get; set; } public int Height { get; set; } public Margin Margin { get; set; } } public class Paragraph : PageContent{ public string Text { get; set; } } public class Table : PageContent{ public int Rows { get; set; } public int Columns { get; set; } //.... more } In my business logic, there are rendering classes for each type public interface IPdfRenderer<T> { T Render(MigraDoc.DocumentObjectModel.Section s); } class ParagraphRenderer : IPdfRenderer<MigraDoc.DocumentObjectModel.Paragraph> { BusinessEntities.PDF.Paragraph paragraph; public ParagraphRenderer(BusinessEntities.PDF.Paragraph p) { paragraph = p; } public MigraDoc.DocumentObjectModel.Paragraph Render(MigraDoc.DocumentObjectModel.Section s) { var paragraph = s.AddParagraph(); // add text from paragraph etc return paragraph; } } public class TableRenderer : IPdfRenderer<MigraDoc.DocumentObjectModel.Tables.Table> { BusinessEntities.PDF.Table table; public TableRenderer(BusinessEntities.PDF.Table t) { table =t; } public MigraDoc.DocumentObjectModel.Tables.Table Render(Section obj) { var table = obj.AddTable(); //fill table based on table } } I want to create a PDF page as : var document = new Document(); var section = document.AddSection();// section is a page in pdf var page = GetPage(1); // get a page from business classes foreach (var content in page.Content) { //var renderer = createRenderer(content); // // get Renderer based on Business type ?? // renderer.Render(section) } For createRenderer() i can use switch case/dictionary and return type. How can i get/create the renderer generically based on type ? How can I use factory or abstract factory here? Or which design pattern better suits this problem?

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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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  • 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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  • Casting Between Data Types in C#

    - by Jimbo
    I have (for example) an object of type A that I want to be able to cast to type B (similar to how you can cast an int to a float) Data types A and B are my own. Is it possible to define the rules by which this casting occurs? Example int a = 1; float b = (float)a; int c = (int)b;

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  • How do I assert that two arbitrary type objects are equivalent, without requiring them to be equal?

    - by Tomas Lycken
    To accomplish this (but failing to do so) I'm reflecting over properties of an expected and actual object and making sure their values are equal. This works as expected as long as their properties are single objects, i.e. not lists, arrays, IEnumerable... If the property is a list of some sort, the test fails (on the Assert.AreEqual(...) inside the for loop). public void WithCorrectModel<TModelType>(TModelType expected, string error = "") where TModelType : class { var actual = _result.ViewData.Model as TModelType; Assert.IsNotNull(actual, error); Assert.IsInstanceOfType(actual, typeof(TModelType), error); foreach (var prop in typeof(TModelType).GetProperties()) { Assert.AreEqual(prop.GetValue(expected, null), prop.GetValue(actual, null), error); } } If dealing with a list property, I would get the expected results if I instead used CollectionAssert.AreEquivalent(...) but that requires me to cast to ICollection, which in turn requries me to know the type listed, which I don't (want to). It also requires me to know which properties are list types, which I don't know how to. So, how should I assert that two objects of an arbitrary type are equivalent? Note: I specifically don't want to require them to be equal, since one comes from my tested object and one is built in my test class to have something to compare with.

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  • Is there a standard .NET exception to throw when a class doesn't implement a required attribute?

    - by a typing monkey
    Suppose I want to throw a new exception when invoking a generic method with a type that doesn't have a required attribute. Is there a .NET exception that's appropriate for this situation, or, more likely, one that would be a suitable ancestor for a custom exception? For example: public static class ClassA { public static T DoSomething<T>(string p) { Type returnType = typeof(T); object[] typeAttributes = returnType.GetCustomAttributes(typeof(SerializableAttribute), true); if ((typeAttributes == null) || (typeAttributes.Length == 0)) { // Is there an exception type in the framework that I should use/inherit from here? throw new Exception("This class doesn't support blah blah blah"); // Maybe ArgumentException? That doesn't seem to fit right. } } } Thanks.

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  • Generic Factorial function in C#

    - by mqpasta
    I want to write a generic function to calculate factorial in C# ... like: static T Factorial<T>(T n) { if (n <= 1) return 1; return Factorial<T>(n - 1); } but obviously having restriction that we can't perform operations on type 'T'. any alternative?

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  • adhoc struct/class in C#?

    - by acidzombie24
    Currently i am using reflection with sql. I find if i want to make a specialize query it is easiest to get the results by creating a new class inheriting from another and adding the 2 members/columns for my specialized query. Then due to reflections in the lib in my c# code i can write foreach(var v in list) { v.AnyMember and v.MyExtraMember) Now instead of having the class scattered around or modifying my main DB.cs file can i define a class inside a function? I know i can create an anonymous object by writing new {name=val, name2=...}; but i need a to pass this class in a generic function func(query, args);

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  • Generic type in generic collection

    - by Brian Triplett
    I have generic type that looks like: public class GenericClass<T, U> where T : IComparable<T> { // Class definition here } I then have a collection of these instances. What is the cleanest way to pass through the type constraints? public class GenericCollection<V> where V : GenericClass<T, U> // This won't compile { private GenericClass<T, U>[] entries; public V this[index] { get{ return this.entries[index]; } } } Is there perhaps a better way to design this? I think that specifying GenericCollection<T, U, V> where V : GenericClass<T, U> seems awkward. Might be my only option though....

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  • Hot to get generic type from object type

    - by Murat
    My Classes are; class BaseClass { } class DerivedClass1 : BaseClass { } class GenericClass<T> { } class DerivedClass2 : BaseClass { GenericClass<DerivedClass1> subItem; } I want to access all fields of DerivedClass2 class. I use System.Reflection and FieldInfo.GetValue() method; Bu I cant get subItem field. FieldInfo.GetValue() method return type is "object". And I cant cast to GenericClass<DerivedClass1> or I cant get DerivedClass1 type. I try this with BaseClass BaseClass instance = FieldInfo.Getvalue(this) as GenericClass<BaseClass>; but instance is null. How to get instance with type or how to get only type?

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  • How to define generic super type for static factory method?

    - by Esko
    If this has already been asked, please link and close this one. I'm currently prototyping a design for a simplified API of a certain another API that's a lot more complex (and potentially dangerous) to use. Considering the related somewhat complex object creation I decided to use static factory methods to simplify the API and I currently have the following which works as expected: public class Glue<T> { private List<Type<T>> types; private Glue() { types = new ArrayList<Type<T>>(); } private static class Type<T> { private T value; /* some other properties, omitted for simplicity */ public Type(T value) { this.value = value; } } public static <T> Glue<T> glueFactory(String name, T first, T second) { Glue<T> g = new Glue<T>(); Type<T> firstType = new Glue.Type<T>(first); Type<T> secondType = new Glue.Type<T>(second); g.types.add(firstType); g.types.add(secondType); /* omitted complex stuff */ return g; } } As said, this works as intended. When the API user (=another developer) types Glue<Horse> strongGlue = Glue.glueFactory("2HP", new Horse(), new Horse()); he gets exactly what he wanted. What I'm missing is that how do I enforce that Horse - or whatever is put into the factory method - always implements both Serializable and Comparable? Simply adding them to factory method's signature using <T extends Comparable<T> & Serializable> doesn't necessarily enforce this rule in all cases, only when this simplified API is used. That's why I'd like to add them to the class' definition and then modify the factory method accordingly. PS: No horses (and definitely no ponies!) were harmed in writing of this question.

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  • What is the "Dispatcher" design pattern?

    - by Ben Farmer
    What is the "dispatcher" pattern and how would I implement it in code? I have a property bag of generic objects and would like to have the retrieval delegated to a generic method. Currently, I have properties looking for a specific key in the bag. For example: private Dictionary<String, Object> Foo { get; set; } private const String WidgetKey = "WIDGETKEY"; public Widget? WidgetItem { get { return Foo.ContainsKey(WidgetKey) ? Foo[WidgetKey] as Widget: null; } set { if (Foo.ContainsKey(WidgetKey)) Foo[WidgetKey] = value; else Foo.Add(WidgetKey, value); } } It was suggested that this could be more generic with the "dispatcher" pattern, but I've been unable to find a good description or example. I'm looking for a more generic way to handle the property bag store/retrieve.

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  • How to pass an IronPython instance method to a (C#) function parameter of type `Func<Foo>`

    - by Daren Thomas
    I am trying to assign an IronPython instance method to a C# Func<Foo> parameter. In C# I would have a method like: public class CSharpClass { public void DoSomething(Func<Foo> something) { var foo = something() } } And call it from IronPython like this: class IronPythonClass: def foobar(): return Foo() CSharpClass().DoSomething(foobar) But I'm getting the following error: TypeError: expected Func[Foo], got instancemethod

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  • Class hierarchy problem (with generic's variance!)

    - by devoured elysium
    The problem: class StatesChain : IState, IHasStateList { private TasksChain tasks = new TasksChain(); ... public IList<IState> States { get { return _taskChain.Tasks; } } IList<ITask> IHasTasksCollection.Tasks { get { return _taskChain.Tasks; } <-- ERROR! You can't do this in C#! I want to return an IList<ITask> from an IList<IStates>. } } Assuming the IList returned will be read-only, I know that what I'm trying to achieve is safe (or is it not?). Is there any way I can accomplish what I'm trying? I wouldn't want to try to implement myself the TasksChain algorithm (again!), as it would be error prone and would lead to code duplication. Maybe I could just define an abstract Chain and then implement both TasksChain and StatesChain from there? Or maybe implementing a Chain<T> class? How would you approach this situation? The Details: I have defined an ITask interface: public interface ITask { bool Run(); ITask FailureTask { get; } } and a IState interface that inherits from ITask: public interface IState : ITask { IState FailureState { get; } } I have also defined an IHasTasksList interface: interface IHasTasksList { List<Tasks> Tasks { get; } } and an IHasStatesList: interface IHasTasksList { List<Tasks> States { get; } } Now, I have defined a TasksChain, that is a class that has some code logic that will manipulate a chain of tasks (beware that TasksChain is itself a kind of ITask!): class TasksChain : ITask, IHasTasksList { IList<ITask> tasks = new List<ITask>(); ... public List<ITask> Tasks { get { return _tasks; } } ... } I am implementing a State the following way: public class State : IState { private readonly TaskChain _taskChain = new TaskChain(); public State(Precondition precondition, Execution execution) { _taskChain.Tasks.Add(precondition); _taskChain.Tasks.Add(execution); } public bool Run() { return _taskChain.Run(); } public IState FailureState { get { return (IState)_taskChain.Tasks[0].FailureTask; } } ITask ITask.FailureTask { get { return FailureState; } } } which, as you can see, makes use of explicit interface implementations to "hide" FailureTask and instead show FailureState property. The problem comes from the fact that I also want to define a StatesChain, that inherits both from IState and IHasStateList (and that also imples ITask and IHasTaskList, implemented as explicit interfaces) and I want it to also hide IHasTaskList's Tasks and only show IHasStateList's States. (What is contained in "The problem" section should really be after this, but I thought puting it first would be way more reader friendly). (pff..long text) Thanks!

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  • To Reference A Generic Method With A Lambda Expression

    - by SDReyes
    It is possible to reference a generic method using a Lambda Expression Object? For example, having: TheObject: public abstract class LambdaExpression : Expression TheMethod (an extension method of LINQ): public static TSource Last<TSource>( this IEnumerable<TSource> source ) I'm trying to create an instance of TheObject, that references to TheMethod. How do you do such thing?

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  • How to perform a binary search on IList<T>?

    - by Daniel Brückner
    Simple question - given an IList<T> how do you perform a binary search without writing the method yourself and without copying the data to a type with build-in binary search support. My current status is the following. List<T>.BinarySearch() is not a member of IList<T> There is no equivalent of the ArrayList.Adapter() method for List<T> IList<T> does not inherit from IList, hence using ArrayList.Adapter() is not possible I tend to believe that is not possible with build-in methods, but I cannot believe that such a basic method is missing from the BCL/FCL. If it is not possible, who can give the shortest, fastest, smartest, or most beatiful binary search implementation for IList<T>? UPDATE We all know that a list must be sorted before using binary search, hence you can assume that it is. But I assume (but did not verify) it is the same problem with sort - how do you sort IList<T>? CONCLUSION There seems to be no build-in binary search for IList<T>. One can use First() and OrderBy() LINQ methods to search and sort, but it will likly have a performance hit. Implementing it yourself (as an extension method) seems the best you can do.

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  • Java generic Comparable where subclasses can't compare to eachother

    - by dege
    public abstract class MyAbs implements Comparable<MyAbs> This would work but then I would be able to compare class A and B with each other if they both extend MyAbs. What I want to accomplish however is the exact opposite. So does anyone know a way to get the generic type to be the own class? Seemed like such a simple thing at first... Edit: To explain it a little further with an example. Say you have an abstract class animals, then you extend it with Dogs and ants. I wouldn't want to compare ants with Dogs but I however would want to compare one dog with another. The dog might have a variable saying what color it is and that is what I want to use in the compareTo method. However when it comes to ants I would rather want to compare ant's size than their color. Hope that clears it up. Could possibly be a design flaw however.

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  • VS2010 Implement Generic Interface expansion doesn't use specified type

    - by TJB
    Using the release version of Visual Studio 2010 I think there's a difference in the "Implement Interface" expansion from VS2008 If I speicify an interface and implement it in a class as so: public interface IRepository<T> where T : IModel { T Get<T>(int id); void Update<T>(); int Add<T>(T item); } public class MockRepository : IRepository<MockUser> { // ... } Then use the "Implement Interface" expansion and get this: public class MockRepository : IRepository<MockUser> { public T Get<T>(int id) { throw new NotImplementedException(); } public void Update<T>() { throw new NotImplementedException(); } public int Add<T>(T item) { throw new NotImplementedException(); } } Instead of what I expected public class MockRepository : IRepository<MockUser> { public MockUser Get<MockUser>(int id) { throw new NotImplementedException(); } public void Update<MockUser>() { throw new NotImplementedException(); } public int Add<MockUser>(MockUser item) { throw new NotImplementedException(); } } The IDE uses the type variable name from the generic interface definition T instead of the specified concrete type MockUser. Is this a bug? Or is something new just for VS2010 / .Net 4.0?

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  • XML Serializing a class with a Dictionary<string, List<string>> object

    - by Matt
    Is it possible to implement IXmlSerializable and in my XML file capture an object of type Dictionary ? I have the following public class coolio : IXmlSerializable { private int a; private bool b; private string c; private Dictionary<string, List<string>> coco; public coolio(int _a, bool _b, string _c, Dictionary<string, List<string>> _coco) { a=_a; b=_b; c=_c; coco=_coco; } public System.Xml.Schema.XmlSchema GetSchema() { return null; } public void WriteXml(XmlWriter writer) { const string myType = "coolio"; writer.WriteStartElement(myType); writer.WriteAttributeString("a", a.ToString()); writer.WriteAttributeString("b", b.ToString()); writer.WriteAttributeString("c", c); // How do I add a subelement for Dictionary<string, List<string>> coco? writer.WriteEndElement(); } public void ReadXml(XmlReader reader) { if (reader.MoveToContent() != XmlNodeType.Element || reader.LocalName != "coolio") return; a= int.Parse(reader["a"]); b = bool.Parse(reader["b"]); c= reader["c"]; // How do I read subelement into Dictionary<string, List<string>> coco? } } But I am stumped as to how I could add the Dictionary (XML seriliazed to my XML file)

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  • Converting non-generic List type to Generic List type in Java 1.5

    - by Shaun F
    I have a List that is guaranteed to contain just one type object. This is created by some underlying code in a library that I cannot update. I want to create a List<ObjectType> based on the incoming List object so that my calling code is talking to List<ObjectType>. What's the best way to convert the List (or any other object collection) to a List<ObjectType>.

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