Reflection and Generics

Brad Abrams Reflection and Generics | work from home

Brad Abrams Reflection and Generics | work from home — Tue, 16 Jun 2009 16:26:07 GMT

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Generics and the special constraints

Brad Abrams — Tue, 05 Oct 2004 06:28:00 GMT

re: Reflection and Generics

J. Ambrose Little — Tue, 22 Jun 2004 12:31:00 GMT

Thanks, Joel. I suppose that once you're aware of it, it's not a big deal, but it did throw me for a loop, especially since the BindGenericParameters example in the current docs didn't have that. I had to go into debug to figure out what the type name actually was.

It would be nice to have it do some sort of search if no arity is indicated, e.g.:
1. Look for a non-generic match first.
2. Look for generic match, going from 1-n arity, matching the first found.

Granted, this might cause more confusion than it's worth, but as long as this or the current format is documented, we'll probably be okay.

Just curious, do you find or expect much overloading on arity?

re: Reflection and Generics

Joel Pobar — Tue, 22 Jun 2004 04:18:00 GMT

Backtick "`" plus integer specifies the arity of the Generic type, and is actually burned in at the metadata level as the string type name. GetType() takes an unmangled string name and simply brings it to life by string comparing over the metadata table. It's unfortunate that we couldn't use angle brackets to specify arity, ala C# syntax, but the C++ folk have already reserved them in the type name grammar. :)

For now, you'll need to specify the string name according to the type name grammar rules (which should be specified in the next revision of the ECMA specification). Which means, Foo`1 for Foo<T>, Foo`2 for Foo<K,V> etc. We may look at adding helper methods for string name mangling sometime in the future.

re: Reflection and Generics

J. Ambrose Little — Tue, 22 Jun 2004 03:22:00 GMT

I ended up using BindGenericParameters:

System.Type constructedType, genericType;
genericType = compiled.CompiledAssembly.GetType(dynamicTypeName + "`1");
constructedType = genericType.BindGenericParameters(new Type[1] {typeof(T)});
comparer = constructedType.GetConstructor(new Type[0] {}).Invoke(null)
as System.Collections.Generic.IComparer<T>;

I am wondering why I have to add the "`1" at the end of my type name to get the generic. I can see that it indicates the number of type parameters, but the example for BindGenericParameters in the docs didn't, IIRC, add that (so its code shouldn't work). Are you guys going to work around this or is this the format you're sticking with?

re: Reflection and Generics

J. Ambrose Little — Tue, 22 Jun 2004 01:25:00 GMT

Brad,

Can you help me out with this problem? I've got some code that is dynamically compiled and loaded into an Assembly type. In the past, I could use myAssembly.CreateInstance to get an instance of a type in the Assembly. But what if the type I need to create requires a type argument? Is there any way to pass that through reflection to get an instance of the type?

Thanks.

re: Reflection and Generics

Mahavir — Tue, 25 May 2004 12:07:00 GMT

Please help me with the questions below :

re: Reflection and Generics

Brad Abrams — Wed, 28 Jan 2004 14:23:00 GMT

Rich -- Yes, this code supports the new constraint...
typeof(System.Runtime.CompilerServices.NewConstraintAttribute))

{

Write("new()");

}

More on Generics from Brad

autoCode( my_dotnet_baby ); — Wed, 28 Jan 2004 12:30:00 GMT

re: Reflection and Generics

RichB — Wed, 28 Jan 2004 11:26:00 GMT

Does your code also work on types which have a constructor constraint?