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POC# Generics on interface
 

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    <p>I'm creating a generic interface to work as command pattern:</p> <pre><code>public interface IGenericComponent&lt;T&gt; where T : IVisitableObject { void Update(T msg); } </code></pre> <p>Then, I'll have another class that I'll hold a bunch of implementations of this interface (each one with its own type). There I would have a dictionary to put the list of commands to execute like this:</p> <pre><code>private Dictionary&lt;MessageType, List&lt;IGenericComponent&gt;&gt; _components; </code></pre> <p>This generates a compilation error because I don't put the type for the IGenericComponent. I have a thread that calls the Update method and a method to subscribe (inserta an component to the dictionary):</p> <pre><code>public void Subscribe&lt;T&gt;(MessageType messageType, IGenericComponent&lt;T&gt; component) where T : IVisitableObject, new() { lock (_monitorDictionary) { List&lt;IGenericComponent&gt; subscribedList; if (_components.TryGetValue(messageType, out subscribedList)) { subscribedList.Add(component); IVisitableObject firstUpdate; if(_messageBuffer.TryGetValue(messageType, out firstUpdate)) component.Update((T)firstUpdate); } else { subscribedList = new List&lt;IGenericComponent&gt;(); subscribedList.Add(component); _components[messageType] = subscribedList; } } } private void ProcessQueue() { while (true) { IVisitableObject msg; lock (_monitorQueue) { msg = _queue.Dequeue(); } List&lt;IGenericComponent&gt; components; lock(_monitorDictionary) { components = _components[msg.MsgType]; } if(components!= null) { foreach (IGenericComponent genericComponent in components) genericComponent.Update(msg); } } } </code></pre> <p>This code does not compile... I came from Java programming, and in Java I can ommit the parametrized type when I instantiate the type. So... I would like to know if is it possible to do that in C# so it would assume that its the generic type (IVisitableObject). Or if you know a better way to solve this problem... The way I've solved this is not the way I would like to use. I've removed generics from the interface and used the generic type IVisitableObject as the parameter of Update method. Thanks in advance.</p>
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    1. COJava does generics completely different from .NET. In Java, generics are pretty much a bit of metadata and some compiler sugar to check for type safety at compile time, emitting typecasts where necessary ("erasure"). In .NET, however, each generic type is built as its own type at runtime; they are just as if you had written the code with the specific type, which is why they also work for value types and primitives (e.g. a `Dictionary<int, double>` etc. doesn't box the key or the value).
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