CODEWITHSUNDEEP
c#reflectioncasting
Lieven Cardoen
Lieven Cardoen

Reputation: 25959

Casting to a Type

I'm wondering if it's possible to cast an object to a Type... I've just started using Reflection, so maybe I'm doing it all wrong but here's what I would like to do:

...
Type type = ...;
Type interfaceType = someOtherType.GetInterface("IConverter`2");

return (Cast to interfaceType)Activator.CreateInstance(type);

Is the cast to the interface possible?

Update:

Compiler says that T and K can not be found. The myInterface Type instance knows the T and K class...

public IConverter<T, K> GetConverter(Type type)
{
    if (dtoModelDictionary.ContainsKey(type))
    {
        Type foundType = dtoModelDictionary[type];
        Type myInterface = foundType.GetInterface("IConverter`2");

        return (IConverter<T, K>)Activator.CreateInstance(foundType); 
    }
    else if (dalModelDictionary.ContainsKey(type))
    {
        Type foundType = dalModelDictionary[type];

        return (IConverter<T, K>)Activator.CreateInstance(foundType);
    }
    else
    {
        throw new System.Exception();
    }
}

Second update:

public SomeClass GetConverter(Type type)
    {
        if (dtoModelDictionary.ContainsKey(type))
        {
            Type foundType = dtoModelDictionary[type];
            Type myInterface = foundType.GetInterface("IConverter`2");

            IConverter<T, K> converter = (IConverter<T, K>)Activator.CreateInstance(foundType); 
            return converter.someMethod(); 
        }
    }

Upvotes: 0

Views: 1115

Answers (4)

eulerfx
eulerfx

Reputation: 37719

You can do this:

var type = typeof(IConverter<,>).MakeGenericType(new Type[] { typeof(T), typeof(K) });

Upvotes: 1

Stefan Steinegger
Stefan Steinegger

Reputation: 64628

Answer to you update:

You cannot cast to a type where the generic arguments are not defined. T and K must be defined for the method that is using it.

Either declare it:

public IConverter<T, K> GetConverter<T, K>(Type type)

Or, if you face the problem often that this interface is used but you don't know any T or K types, use an interface without generics:

interface IConverter
{ 
  // general members
}

interface  IConverter<T, K> : IConverter 
{
  // typesave members
}

public IConverter GetConverter(Type type)
{
  // ...
  return (IConverter)Activator.CreateInstance(type);
}

Upvotes: 3

Guffa
Guffa

Reputation: 700342

You can only cast an object to something that it actually is. You can for example cast a String reference to IEnumerable, but you can't cast it to char[].

If what your method returns actually implements the interface, you can just cast it as usual.

Example:

return (IConverter<int,string>)Activator.CreateInstance(type);

Edit:
You need to make the method generic so that you can specify the data types when you call it:

public IConverter<T, K> GetConverter<T, K>(Type type) {
   ...
}

Upvotes: 1

ZeroBugBounce
ZeroBugBounce

Reputation: 3670

Not really, no... at least not in this way. The problem is that your return value is going to have to be whatever your method's return value is typed as. Because everything must be typed at compile-time, there is limited or no real use case that I can see for this particular kind of type coersion - maybe you can say some more about what you are trying to accomplish?

Now if you are using generics, you do have a run-time typing story, you can return your Type parameter type:

public T MyMethod<T>(...)
...
return (T)Activator.CreateInstance(type);

Upvotes: 1

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