C# how to get type of generic class using reflection

In the following example, given an instance of SystemFolder, how would you find the generic type 
Folder given that SystemFolder : IDropTarget<Folder>?

using System;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Linq;
 
namespace CSharpGenerics
{

public class GenericUtilities
    {
        // Example Type type = GenericUtilities.GetGenericType(new SystemFolder()); will return Folder
        public static Type GetGenericType(object @object)
        {
            var type = @object.GetType();
            var iDropTargetObject = type.GetInterfaces().
FirstOrDefault(x => x.IsGenericType && x.GetGenericTypeDefinition() == typeof(IDropTarget<>));
            Debug.Assert(iDropTargetObject != null);
            return iDropTargetObject.GetGenericArguments()[0];
        }
    }

    public class SystemFolder : IDropTarget<Folder>
    {
        public SystemFolder()
        {
            Items = new Collection<Folder>();
        }
 
        public Collection<Folder> Items { get; set; }
 
        #region IDropTarget Members
 
        public string Name
        {
            get { return "My Drop Target"; }
        }
 
        public void Add(Folder item)
        {
            Items.Add(item);
        }
 
        #endregion IDropTarget Members
    }
 
    public class Folder
    {
    }
 
    public interface IDropTarget
    {
        string Name { get; }
 
        void Add(T item);
    }
}

Test Class

using Microsoft.VisualStudio.TestTools.UnitTesting;
 
namespace CSharpGenerics.Tests
{
    [TestClass]
    public class SystemFolderTest
    {
        [TestMethod]
        public void GetGenericType()
        {
            // Act
            var genericType = GenericUtilities.GetGenericType(new SystemFolder());
 
           // Assert
            Assert.AreEqual(genericType, typeof(Folder));
 
        }
    }
}