foo1.cs

    [NotNull, Pure]
    public static string Present(this TypeKind kind) {
      switch (kind) {
        case TypeKind.StaticClass:   return "S";
        case TypeKind.AbstractClass: return "A";
        case TypeKind.Interface:     return "I";
        case TypeKind.Enumeration:   return "E";
        case TypeKind.ValueType:     return "V";
        default:                     return "C";
      }
    }

foo2.cs

    [NotNull, Pure]
    public static string Present(this TypeKind kind) {
      return kind switch {
        TypeKind.StaticClass   => "S",
        TypeKind.AbstractClass => "A",
        TypeKind.Interface     => "I",
        TypeKind.Enumeration   => "E",
        TypeKind.ValueType     => "V",
        _                      => "C"
      }
    }