using System; using System.Linq.Expressions; class ConversionTest { static int Main () { byte b = 3; FormattableString c1; c1 = $"{b}"; if (c1.Format != "{0}") return 1; IFormattable c2; c2 = $"format { b }"; if (!(c2 is FormattableString)) return 2; return 0; } }