Generic type from string value
Solution 1
I figured it out, I used InvokeMember to access it. :)
typeHandler.InvokeMember("Handle", BindingFlags.InvokeMethod, null, handler, new[] { requestItem });
Solution 2
You need Type.MakeGenericType
:
Type typeArgument = Type.GetType(string.Format("Mynamespace.{0}", typeString));
Type template = typeof(MyClass<>);
Type genericType = template.MakeGenericType(typeArgument);
object instance = Activator.CreateInstance(genericType);
Note that you can't cast this to a particular MyClass<T>
because you don't know T
- but it will be an instance of the right class at execution time.
Solution 3
Type closedType = typeof(MyClass<>).MakeGenericType(myGeneric);
object obj = Activator.CreateInstance(closedType);
Note that unless you have a non-generic interface or base-type, it is very tricky to talk to this type of object (unless you cheat by using dynamic
). For example, a non-generic interface can be helpful:
var obj = (ISomeInterface)Activator.CreateInstance(closedType);
obj.SomeMethodOnTheNonGenericInterface();
Rik De Peuter
Updated on July 06, 2022Comments
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Rik De Peuter almost 2 years
I got a custom class, who relies on a generic type T to be passed along. I only know what type it is in string form, because that's how it's being sent. I've been searching around but can't seem to find exactly what I need. I can parse the string value to a type, but I need to parse it to... something, that I can pass as a generic parameter.
I've rewritten my problem, as such:
// Classes structure namespace Mynamespace { public interface IRequest { } public interface IHandler<T> where T : IRequest { void Handle(T item); } public class MyRequest : IRequest { } public class MyHandler : IHandler<MyRequest> { void Handle(MyRequest item) { } } } // The info I get, and I know typeString is a IRequest string typeString = "My"; object requestItem = [insert xml parsing here]; // I then create a handler, to handle the request Type typeHandler = Type.GetType("Mynamespace." + typeString + "Handler"); var handler = Activator.CreateInstance(typeHandler); Type typeRequest = Type.GetType("Mynamespace." + typeString + "Request"); // what I want to do: handler.Handle(requestItem);
I can't do that because handler and requestItem are just objects So I need to parse 'handler' to 'typeHandler', and requestItem to 'typeRequest'
Edit: I figured it out, I used InvokeMember to access it. :)
typeHandler.InvokeMember("Handle", BindingFlags.InvokeMethod, null, handler, new[] { requestItem });
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Daniel Pryden over 12 years+1. Also note that, although you can't cast the result to a particular
MyClass<T>
, you may want to define a non-generic interface (e.g.IMyClass
) and cast to that. -
Jon Skeet over 12 years@Daniel: Indeed. I thought I'd hold back from that until the OP gave more information :)
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Rik De Peuter over 12 yearsThis is what I sort of do as well already, to create a new instance. But that returns an object, and that object, I need to parse to a MyClass<T>. Because the 'MyClass' has a void that requires the T.
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Rik De Peuter over 12 years@Daniel: In my real code I use an interface, and an extra class in between, but I tried here to make a sample of what my problem is, without making it too complicated. :)
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Daniel Pryden over 12 years@FrieK: What do you mean, "has a void that requires the T"? You aren't going to be able to use compile-time generic dispatch based on a type that is only determined at run time -- it's simply not possible. Perhaps
dynamic
will do what you want, but I don't understand your problem well enough to be sure. -
Rik De Peuter over 12 yearsHmm, I think it's the impossible one that I want, but I am rewriting my question to make it more obvious, I hope.
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Rik De Peuter over 12 yearsHi Daniel, I've rewritten my problem, maybe it will make more sense like that. :) Thanks again!