如何使用roslyn获得泛型类的运行时类型？

Question

For example I have the following type:

public class MyClass<T>
{
    public T Prop { get; }
}

Or let say I have the following method:

private static void Method<T>() 
{
     //how I can get a real type of <T>
}

How can I get a run-time type of generic class using roslyn ? I mean real type of <T>

static void Main(string[] args)
{
    // here I need to get int
    var m = new MyClass<int>();

    // here I need to get object
    var m1 = new MyClass<object>();
}

Answer 1

If you have the MyClass syntax tree and you want to get the concrete type or instantiated type of ITypeParameterSymbol T , the simple answer is, you can't do it with Roslyn.

If you mean how to get the type from instantiation like this new MyClass<int>() , the answer is:

var genericType = // the ObjectCreationExpressionSyntax from type GenericNameSyntax
var typArg = genericType.TypeArgumentList.Arguments.First();
var type = model.GetSymbolInfo(typeArg).Symbol // this is your concrete type

You can also parse the IdentifierName or TypeSyntax in the TypeArgument but it's syntactically, not semantically.

Update

Please explain from which point of view you want to get the info about the run-time type.

As I wrote, if you hold the syntax tree of MyClass<T> (in your example) you can't get any info. Roslyn can tell you that is a generic type but that it. The only way to get this info is in run-time (for example, if you in debug mode and you set a breakpoint somewhere in this class and inspect the type of T in the watch window).

If you want to get the type from instanciated syntax like var m = new MyClass<int>() in your example, it's easy as I answered.