c-sharp-switch-expression-when.cs

            var userType = "";

            var result = userType switch
            {
               //要使用 when 關鍵字來使用
                var t when string.IsNullOrEmpty(t) => "DEFAULT",
                "PLUS" => "CALL_PLUS",
                "PREMIUM" => "CALL_PREMIUM",
                "Ultimate" => "CALL_ULTIMATE",
                _ => "CALL_DEFAULT"
            };