Program.cs

using System;
using System.Runtime.CompilerServices;

namespace LeakTest
{
	public class MemoryLeakCheck<T> where T : class
	{
		string filename;
		int lineNumber;
		WeakReference<T> reference;

		public MemoryLeakCheck(T theObject, [CallerFilePath] string filename = "",
					[CallerLineNumber] int lineNumber = 0)
		{
			this.reference = new WeakReference<T>(theObject);
			this.filename = filename;
			this.lineNumber = lineNumber;
		}

		public bool Check()
		{
			GC.Collect();
			GC.WaitForPendingFinalizers();

			T theObject = null;

			reference.TryGetTarget(out theObject);
			bool isAlive = theObject != null;

			if (isAlive)
			{
				Console.WriteLine($"Object allocated at {filename}-{lineNumber} is still alive.");
			}

			return isAlive;
		}
	}

	class Foo
	{
		public Foo(string name)
		{
			_name = name;
		}

		string _name;

		public override string ToString() => "Foo " + _name;

		~Foo()
		{
			Console.WriteLine("Foo " + _name + " is being finalized");
		}
	}

	class Bar
	{
		public Bar(Foo foo)
		{
			TheFoo = foo;
		}
		public Foo TheFoo { get; set; }

		public void BarIt()
		{
			Console.WriteLine("That's my foo: " + TheFoo);
			TheFoo = null;
			Console.WriteLine("Verifying that Foo is null: " + (TheFoo == null));
		}
	}

	class MainClass
	{
		public static void Main(string[] args)
		{

				var o1 = new Bar(new Foo("1"));
				var o2 = new Bar(new Foo("2"));

				var wr1 = new MemoryLeakCheck<Foo>(o1.TheFoo);
				var wr2 = new MemoryLeakCheck<Foo>(o2.TheFoo);

				o1.BarIt();
				o1 = null;

				Console.WriteLine($"o1: {wr1.Check()}");
				Console.WriteLine($"o2: {wr2.Check()}");
		
			Console.ReadKey();
		}
	}
}