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Invoke a Type From Dictionary<T>

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  • User profile image
    phreaks

    Still trying to get a good handle on generics.

    Trying to migrate all my non-generic code to run more efficiently and really take advantgage of Generics and I am running into some headaches.

    I used to Load objects by adding them to a dictionary as an Instance.

    === Sample ===
    Dictionary<String, BaseClass> _objDict = new Dictionary<String, BaseClass>();

    _objDict.Add("ConcreteClass1", new ConcreteClass1());
    _objDict.Add("ConcreteClass2", new ConcreteClass2());

    === /End ===

    Now I am trying something like:

    === New Sample ===

    private Dictionary<Type, Type> _objects = new Dictionary<Type, Type>();

    _objects.Add(typeof(MyNamespace.ConcreteClass1), typeof(Frames.DateRangeFrame));
    _objects.Add(
    typeof(MyNamespace.ConcreteClass2), typeof(Frames.DateFrame));

    === /End  ===

    The goal is to be able to get an instance of the key and value Types conatined in the Dictionary.

    Am I thinking about this right? Is there a better way? How would I even get an instance of the Type this way?

    I don't know what types I need until run-time and don't want the overhead of keeping initialized instances around in the Collection.

    //EDIT: also, if anyone can recommend a good book/video on generics, I would appreciatte it.

  • User profile image
    ronin1855

    If you are going to do it that way, you need to use reflection to create an instance of the type you are trying to get -- OOPs the generic activitator won't work because you need to pass in a type parameter at compile time, and you said you won't know till runtime. Use this instead Activator.CreateInstance(Type). Then invoke the instance.

    It sounds like you are looking for a strategy pattern or the provider pattern. You should look into those patterns, and you'll get a better idea of how to design your classes. http://dofactory.com/Patterns/Patterns.aspx, has quick & dirty examples of different patterns check it out, and then you can look at other docs

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