using System;

public class Program

{

    public partial interface IUnionSample<T>

    {

        public T Key { get; set; }

    }

​

    public partial class FooClass : IUnionSample<string>

    {

        public int XYZ { get; set; }

        public string Key { get; set; }

    }

​

    public partial class BarClass : IUnionSample<string>

    {

        public string? OPQ { get; set; }

        public string Key { get; set; }

    }

    public static void Main()

    {

        Console.WriteLine(typeof(IUnionSample).IsGenericType);

    }

}