detect escaped json-string, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Microsoft (R) Visual C# Compiler version 2.9.0.63208 (958f2354)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using Newtonsoft.Json;

namespace Rextester
{
    public class Program
    {
        //is escaped or unescaped?
        public static bool isEscaped(string str){
            try{
                JsonConvert.DeserializeObject<string>(str);
                return ( (str[0]=='"') && (str[str.Length-1]=='"') ); //if double quotes at beginning and in the end
            }
            catch{
                return false;
            }
        }
        
        public static void Main(string[] args)
        {
            //Your code goes here
            string str = "Hello, world!'\"\r\n()!";
            string json = JsonConvert.SerializeObject(str);
            Console.WriteLine("str: "+str);
            Console.WriteLine("JsonString: "+json);
            string str2 = JsonConvert.DeserializeObject<string>(json);
            Console.WriteLine("str2: "+str2);
            Console.WriteLine("strings equals? (str== str2): "+(str==str2));
            
            string str3 = "";
            
            //str
            str3 = str;
            Console.WriteLine( "isEscaped(str3)? " + isEscaped(str3) ); // False

//json
            str3 = json;
            Console.WriteLine( "isEscaped(str3)? " + isEscaped(str3) ); // True
        }
    }
}

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Compilation time: 0,64 sec, absolute running time: 0,69 sec, cpu time: 0,38 sec, average memory usage: 24 Mb, average nr of threads: 4, absolute service time: 1,36 sec