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  • LINQ-to-SQL: Searching against a CSV

    - by Peter Bridger
    I'm using LINQtoSQL and I want to return a list of matching records for a CSV contains a list of IDs to match. The following code is my starting point, having turned a CSV string in a string array, then into a generic list (which I thought LINQ would like) - but it doesn't: Error Error 22 Operator '==' cannot be applied to operands of type 'int' and 'System.Collections.Generic.List<int>' C:\Documents and Settings\....\Search.cs 41 42 C:\...\ Code DataContext db = new DataContext(); List<int> geographyList = new List<int>( Convert.ToInt32(geography.Split(',')) ); var geographyMatches = from cg in db.ContactGeographies where cg.GeographyId == geographyList select new { cg.ContactId }; Where do I go from here?

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  • Generic <T> how cast ?

    - by Kris-I
    Hi, I have a "Product" base class, some other classes "ProductBookDetail","ProductDVDDetail" inherit from this class. I use a ProductService class to make operation on these classes. But, I have to do some check depending of the type (ISBN for Book, languages for DVD). I'd like to know the best way to cast "productDetail" value, I receive in SaveOrupdate. I tried GetType() and cast with (ProductBookDetail)productDetail but that's not work. Thanks, var productDetail = new ProductDetailBook() { .... }; var service = IoC.Resolve<IProductServiceGeneric<ProductDetailBook>>(); service.SaveOrUpdate(productDetail); var productDetail = new ProductDetailDVD() { .... }; var service = IoC.Resolve<IProductServiceGeneric<ProductDetailDVD>>(); service.SaveOrUpdate(productDetail); public class ProductServiceGeneric<T> : IProductServiceGeneric<T> { private readonly ISession _session; private readonly IProductRepoGeneric<T> _repo; public ProductServiceGeneric() { _session = UnitOfWork.CurrentSession; _repo = IoC.Resolve<IProductRepoGeneric<T>>(); } public void SaveOrUpdate(T productDetail) { using (ITransaction tx = _session.BeginTransaction()) { //here i'd like ot know the type and access properties depending of the class _repo.SaveOrUpdate(productDetail); tx.Commit(); } } }

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  • how to make accessor for Dictionary in a way that returned Dictionary cannot be changed C# / 2.0

    - by matti
    I thought of solution below because the collection is very very small. But what if it was big? private Dictionary<string, OfTable> _folderData = new Dictionary<string, OfTable>(); public Dictionary<string, OfTable> FolderData { get { return new Dictionary<string,OfTable>(_folderData); } } With List you can make: public class MyClass { private List<int> _items = new List<int>(); public IList<int> Items { get { return _items.AsReadOnly(); } } } That would be nice! Thanks in advance, Cheers & BR - Matti NOW WHEN I THINK THE OBJECTS IN COLLECTION ARE IN HEAP. SO MY SOLUTION DOES NOT PREVENT THE CALLER TO MODIFY THEM!!! CAUSE BOTH Dictionary s CONTAIN REFERENCES TO SAME OBJECT. DOES THIS APPLY TO List EXAMPLE ABOVE? class OfTable { private string _wTableName; private int _table; private List<int> _classes; private string _label; public OfTable() { _classes = new List<int>(); } public int Table { get { return _table; } set { _table = value; } } public List<int> Classes { get { return _classes; } set { _classes = value; } } public string Label { get { return _label; } set { _label = value; } } } so how to make this immutable??

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  • How do I put all types implementing a certain generic interface in a dictionary?

    - by James Wenday
    Given a particular interface ITarget<T> and a particular type myType, here's how you would determine T if myType implements ITarget<T>. (This code snippet is taken from the answer to an earlier question.) foreach (var i in myType.GetInterfaces ()) if (i.IsGenericType && i.GetGenericTypeDefinition() == typeof(ITarget<>)) return i.GetGenericArguments ()[0] ; However, this only checks a single type, myType. How would I create a dictionary of all such type parameters, where the key is T and the value is myType? I think it would look something like this: var searchTarget = typeof(ITarget<>); var dict = Assembly.GetExecutingAssembly().[???] .Where(t => t.IsGenericType && t.GetGenericTypeDefinition() == searchTarget) .[???]; What goes in the blanks?

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  • Java class Class<T> and static method Class.forName() drive me crazy.

    - by matt
    Hi, this code doesn't compile. i'm wandering what i am doing wrong: private static Importable getRightInstance(String s) throws Exception { Class<Importable> c = Class.forName(s); Importable i = c.newInstance(); return i; } where Importable is an interface and the string s is the name of an implementing class. The compiler says: ./Importer.java:33: incompatible types found : java.lang.Class<capture#964 of ?> required: java.lang.Class<Importable> Class<Importable> c = Class.forName(format(s)); thanks for any help!

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  • Improve this generic abstract class

    - by Keivan
    I have the following abstract class design, I was wondering if anyone can suggest any improvements in terms of stronger enforcement of our requirements or simplifying implementing of the ControllerBase. //Dependency Provider base public abstract class ControllerBase<TContract, TType> where TType : TContract, class { public static TContract Instance { get { return ComponentFactory.GetComponent<TContract, TType>(); } } public TContract GetComponent<TContract, TType>() where TType : TContract, class { component = (TType)Activator.CreateInstance(typeof(TType), true); RegisterComponentInstance<TContract>(component); } } //Contract public interface IController { void DoThing(); } //Actual Class Logic public class Controller: ControllerBase<IController,Controller> { public void DoThing(); //internal constructor internal Controller(){} } //Usage public static void Main() { Controller.Instance.DoThing(); } The following facts should always be true, TType should always implement TContract (Enforced using a generic constraint) TContract must be an interface (Can't find a way to enforce it) TType shouldn't have public constructor, just an internal one, is there any way to Enforce that using ControllerBase? TType must be an concrete class (Didn't include New() as a generic constrain since the constructors should be marked as Internal)

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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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  • Semi-generic function

    - by Fredrik Ullner
    I have a bunch of overloaded functions that operate on certain data types such as int, double and strings. Most of these functions perform the same action, where only a specific set of data types are allowed. That means I cannot create a simple generic template function as I lose type safety (and potentially incurring a run-time problem for validation within the function). Is it possible to create a "semi-generic compile time type safe function"? If so, how? If not, is this something that will come up in C++0x? An (non-valid) idea; template <typename T, restrict: int, std::string > void foo(T bar); ... foo((int)0); // OK foo((std::string)"foobar"); // OK foo((double)0.0); // Compile Error Note: I realize I could create a class that has overloaded constructors and assignment operators and pass a variable of that class instead to the function.

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  • Extension method question. Why do I need to use someObj = someObj.somemethod();

    - by Kettenbach
    Hi All, I have a simple extension method that I would like to use to add an item to an array of items. public static T[] addElement<T>(this T[] array, T elementToAdd) { var list = new List<T>(array) {elementToAdd}; return list.ToArray(); } this works ok, but when I use it, I am having to set the array equal to the return value. I see that I am returning an Array. I likely want this method to be void, but I would like the item added. Does anyone have any ideas on what I need to do , to make this work the way I am wanting? Instead of someArray = someArray.addElement(item), I just want to do someArray.addElement(item) and then someArray be ready to go. What am I missing here? Thanks, ~ck in San Diego

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  • Inheritance and type parameters of Traversable

    - by Jesper
    I'm studying the source code of the Scala 2.8 collection classes. I have questions about the hierarchy of scala.collection.Traversable. Look at the following declarations: package scala.collection trait Traversable[+A] extends TraversableLike[A, Traversable[A]] with GenericTraversableTemplate[A, Traversable] trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr] with TraversableOnce[A] package scala.collection.generic trait HasNewBuilder[+A, +Repr] trait GenericTraversableTemplate[+A, +CC[X] <: Traversable[X]] extends HasNewBuilder[A, CC[A] @uncheckedVariance] Question: Why does Traversable extend GenericTraversableTemplate with type parameters [A, Traversable] - why not [A, Traversable[A]]? I tried some experimenting with a small program with the same structure and got a strange error message when I tried to change it to Traversable[A]: error: Traversable[A] takes no type parameters, expected: one I guess that the use of the @uncheckedVariance annotation in GenericTraversableTemplate also has to do with this? (That seems like a kind of potentially unsafe hack to force things to work...). Question: When you look at the hierarchy, you see that Traversable inherits HasNewBuilder twice (once via TraversableLike and once via GenericTraversableTemplate), but with slightly different type parameters. How does this work exactly? Why don't the different type parameters cause an error?

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  • Why is TreeSet<T> an internal type in .NET?

    - by Justin Niessner
    So, I was just digging around Reflector trying to find the implementation details of HashSet (out of sheer curiosity based on the answer to another question here) and noticed the following: internal class TreeSet<T> : ICollection<T>, IEnumerable<T>, ICollection, IEnumerable, ISerializable, IDeserializationCallback Without looking too deep into the details, it looks like a Self-Balancing Binary Search Tree. My question is, is there anybody out there with the insight as to why this class is internal? Is it simply because the other collection types use it internally and hide the complexities of a BST from the general masses...or am I way off base?

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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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  • MSMQ - Message Queue Abstraction and Pattern

    - by Maxim Gershkovich
    Hi All, Let me define the problem first and why a messagequeue has been chosen. I have a datalayer that will be transactional and EXTREMELY insert heavy and rather then attempt to deal with these issues when they occur I am hoping to implement my application from the ground up with this in mind. I have decided to tackle this problem by using the Microsoft Message Queue and perform inserts as time permits asynchronously. However I quickly ran into a problem. Certain inserts that I perform may need to be recalled (ie: retrieved) immediately (imagine this is for POS system and what happens if you need to recall the last transaction - one that still hasn’t been inserted). The way I decided to tackle this problem is by abstracting the MessageQueue and combining it in my data access layer thereby creating the illusion of a single set of data being returned to the user of the datalayer (I have considered the other issues that occur in such a scenario (ie: essentially dirty reads and such) and have concluded for my purposes I can control these issues). However this is where things get a little nasty... I’ve worked out how to get the messages back and such (trivial enough problem) but where I am stuck is; how do I create a generic (or at least somewhat generic) way of querying my message queue? One where I can minimize the duplication between the SQL queries and MessageQueue queries. I have considered using LINQ (but have very limited understanding of the technology) and have also attempted an implementation with Predicates which so far is pretty smelly. Are there any patterns for such a problem that I can utilize? Am I going about this the wrong way? Does anyone have an of their own ideas about how I can tackle this problem? Does anyone even understand what I am talking about? :-) Any and ALL input would be highly appreciated and seriously considered… Thanks again.

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  • Generic Class Vb.net

    - by KoolKabin
    hi guys, I am stuck with a problem about generic classes. I am confused how I call the constructor with parameters. My interface: Public Interface IDBObject Sub [Get](ByRef DataRow As DataRow) Property UIN() As Integer End Interface My Child Class: Public Class User Implements IDBObject Public Sub [Get](ByRef DataRow As System.Data.DataRow) Implements IDBObject.Get End Sub Public Property UIN() As Integer Implements IDBObject.UIN Get End Get Set(ByVal value As Integer) End Set End Property End Class My Next Class: Public Class Users Inherits DBLayer(Of User) #Region " Standard Methods " #End Region End Class My DBObject Class: Public Class DBLayer(Of DBObject As {New, IDBObject}) Public Shared Function GetData() As List(Of DBObject) Dim QueryString As String = "SELECT * ***;" Dim Dataset As DataSet = New DataSet() Dim DataList As List(Of DBObject) = New List(Of DBObject) Try Dataset = Query(QueryString) For Each DataRow As DataRow In Dataset.Tables(0).Rows **DataList.Add(New DBObject(DataRow))** Next Catch ex As Exception DataList = Nothing End Try Return DataList End Function End Class I get error in the starred area of the DBLayer Object. What might be the possible reason? what can I do to fix it? I even want to add New(byval someval as datatype) in IDBObject interface for overloading construction. but it also gives an error? how can i do it? Adding Sub New(ByVal DataRow As DataRow) in IDBObject producess following error 'Sub New' cannot be declared in an interface. Error Produced in DBLayer Object line: DataList.Add(New DBObject(DataRow)) Msg: Arguments cannot be passed to a 'New' used on a type parameter.

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  • Using a Type object to create a generic

    - by Richard Neil Ilagan
    Hello all! I'm trying to create an instance of a generic class using a Type object. Basically, I'll have a collection of objects of varying types at runtime, and since there's no way for sure to know what types they exactly will be, I'm thinking that I'll have to use Reflection. I was working on something like: Type elType = Type.GetType(obj); Type genType = typeof(GenericType<>).MakeGenericType(elType); object obj = Activator.CreateInstance(genType); Which is well and good. ^_^ The problem is, I'd like to access a method of my GenericType< instance, which I can't because it's typed as an object class. I can't find a way to cast it obj into the specific GenericType<, because that was the problem in the first place (i.e., I just can't put in something like:) ((GenericType<elType>)obj).MyMethod(); How should one go about tackling this problem? Many thanks! ^_^

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  • Why membership provider is not generic?

    - by Timmy O' Tool
    I have to confess that I hate membership provider. The default implementation is not very appropriate normally and I haven't seen so far a good implementation of a custom membership provider, probably because this is not possible :-) So the question is: In your opinion: which are the reasons for not having membership/role provider as a generic class? I mean, why Microsoft didn't selected this approach.

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  • C# - implementing GetEnumerator() for a collection inherited from List<string>

    - by Vojtech
    Hi, I am trying to implement FilePathCollection. Its items would be simple file names (without a path - such as "image.jpg"). Once the collection is used via foreach cycle, it should return the full path created by concatenating with "baseDirectory". How can I do that? public class FilePathCollection : List<string> { string baseDirectory; public FileCollection(string baseDirectory) { this.baseDirectory = baseDirectory; } new public System.Collections.IEnumerator GetEnumerator() { foreach (string value in this._list) //this does not work because _list is private yield return baseDirectory + value; } } Thanks in advance! :-)

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  • C# Get Keys from a Dictionary<string, Stream>

    - by alex
    Suppose I have a Dictionary like so: Dictionary<string, Stream> How can I get a list (or IEnumerable or whatever) of JUST the Keys from this dictionary? Is this possible? I could enumerate the dictionary, and extract the keys one by one, but I was hoping to avoid this. In my instance, the Dictionary contains a list of filenames (file1.doc, filex.bmp etc...) and the stream content of the file from another part of the application.

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  • Is converting this ArrayList to a Generic List efficient?

    - by Greg
    The code I'm writing receives an ArrayList from unmanaged code, and this ArrayList will always contain one or more objects of type Grid_Heading_Blk. I've considered changing this ArrayList to a generic List, but I'm unsure if the conversion operation will be so expensive as to nullify the benefits of working with the generic list. Currently, I'm just running a foreach (Grid_Heading_Blk in myArrayList) operation to work with the ArrayList contents after passing the ArrayList to the class that will use it. Should I convert the ArrayList to a generic typed list? And if so, what is the most efficient way of doing so?

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  • how do I best create a set of list classes to match my business objects

    - by ken-forslund
    I'm a bit fuzzy on the best way to solve the problem of needing a list for each of my business objects that implements some overridden functions. Here's the setup: I have a baseObject that sets up database, and has its proper Dispose() method All my other business objects inherit from it, and if necessary, override Dispose() Some of these classes also contain arrays (lists) of other objects. So I create a class that holds a List of these. I'm aware I could just use the generic List, but that doesn't let me add extra features like Dispose() so it will loop through and clean up. So if I had objects called User, Project and Schedule, I would create UserList, ProjectList, ScheduleList. In the past, I have simply had these inherit from List< with the appropriate class named and then written the pile of common functions I wanted it to have, like Dispose(). this meant I would verify by hand, that each of these List classes had the same set of methods. Some of these classes had pretty simple versions of these methods that could have been inherited from a base list class. I could write an interface, to force me to ensure that each of my List classes has the same functions, but interfaces don't let me write common base functions that SOME of the lists might override. I had tried to write a baseObjectList that inherited from List, and then make my other Lists inherit from that, but there are issues with that (which is really why I came here). One of which was trying to use the Find() method with a predicate. I've simplified the problem down to just a discussion of Dispose() method on the list that loops through and disposes its contents, but in reality, I have several other common functions that I want all my lists to have. What's the best practice to solve this organizational matter?

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  • Casting Type array to Generic array?

    - by George R
    The short version of the question - why can't I do this? I'm restricted to .NET 3.5. T[] genericArray; // Obviously T should be float! genericArray = new T[3]{ 1.0f, 2.0f, 0.0f }; // Can't do this either, why the hell not genericArray = new float[3]{ 1.0f, 2.0f, 0.0f }; Longer version - I'm working with the Unity engine here, although that's not important. What is - I'm trying to throw conversion between its fixed Vector2 (2 floats) and Vector3 (3 floats) and my generic Vector< class. I can't cast types directly to a generic array. using UnityEngine; public struct Vector { private readonly T[] _axes; #region Constructors public Vector(int axisCount) { this._axes = new T[axisCount]; } public Vector(T x, T y) { this._axes = new T[2] { x, y }; } public Vector(T x, T y, T z) { this._axes = new T[3]{x, y, z}; } public Vector(Vector2 vector2) { // This doesn't work this._axes = new T[2] { vector2.x, vector2.y }; } public Vector(Vector3 vector3) { // Nor does this this._axes = new T[3] { vector3.x, vector3.y, vector3.z }; } #endregion #region Properties public T this[int i] { get { return _axes[i]; } set { _axes[i] = value; } } public T X { get { return _axes[0];} set { _axes[0] = value; } } public T Y { get { return _axes[1]; } set { _axes[1] = value; } } public T Z { get { return this._axes.Length (Vector2 vector2) { Vector vector = new Vector(vector2); return vector; } public static explicit operator Vector(Vector3 vector3) { Vector vector = new Vector(vector3); return vector; } #endregion }

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