Repro.cs

using System;

namespace ConsoleApp1
{
    interface IBar
    {
        void Foo();
    }
    class Program : IBar
    {
        string _foo = "wignew";
        static void Main(string[] args)
        {
        }

        void IBar.Foo()
        {
            lock (_foo)
            {
                Console.WriteLine();
            }
        }
    }
}