Program.cs

int theNumber=new Random().Next(20);
bool keepGoing=true;
Console.WriteLine("Let's play 'Guess the Number!'");
Console.WriteLine("I am thinking of a number between 0 and 20.");
Console.WriteLine("Enter your guess, or -1 to give up");
int guessNum=0;
int guessCount=0;
do{
Console.WriteLine("what's your guess?");
string theGuess=Console.ReadLine();
bool result=Int32.TryParse(theGuess, out guessNum);
if (!result)
{
    Console.WriteLine("That does not look like a number . Try again.");
}
else{
    if(guessNum == -1)
    {
        Console.WriteLine("I was thinking of {theNumber}");
        keepGoing=false;
    }
    else 
    {
        guessCount++;
    }
    if (guessNum==theNumber)
    {
        Console.WriteLine($"You got it in {guessCount} guesses!!");
        keepGoing=false ;
    }

        else
        {
            Console.WriteLine("Nope, {0} than that",guessNum<theNumber?"higher":"lower");
            
            }
        
    }
}
while(keepGoing);