How do make this C# program keep looping until the user has entered an integer?

Question

I want the program to keep asking the user to put in a number until they finally use the correct data type, instead of just exiting the program. This is what I have written.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace test1
{
    class Program
    {
        static void Main(string[] args)
        {
            //declare and initialize variables
            int a = 0;
            int b = 0;
            int area = 0;
            string read;
            
            do { 
                try
                {
                    //input data solicited
                    Console.WriteLine("Rectangle height: ");
                    read = Console.ReadLine();
                    a = int.Parse(line);

                    Console.WriteLine("Rectangle width: ");
                    read = Console.ReadLine();
                    b = int.Parse(line);

                    //operation
                    area = a * b;

                    //print result
                    Console.WriteLine("The area of the rectangle is: " + area + " cm²");
                    
                }
                catch (Exception e)
                {
                    Console.WriteLine("ERROR. Wrong data type.");
                }
            }while (e);
        }
    }
} 

I tried using a boolean as a random guess to make the do-while loop keep going until the user successfully entered a whole number but that didn't work either. The while (e); you see at the bottom was also a wild guess.

                    Console.WriteLine("The area of the rectangle is: " + area + " cm²");
                    cont = false; 
                    
                }
                catch (Exception e)
                {
                    Console.WriteLine("ERROR. Ingresa un numero entero.");
                    cont = false; 
                }
            }while (cont);

I can't use if statements for this.

Answer 1

There's two ways to make it loop until number.

One way is to create a bool starting with false and then loop until the bool is true, so if succeed, then doesn't continue the loop.

And another way is to create a do {} while (true) but with break on end of try stack.

Since that to the code reach at the end (being break or isValid = true), it would need the code to work correctly.

If you prefer, you can replace try {} with a variable type check, if it's a number, then proceed, if anything else, continue to loop (with negate condition).

Using variable

...
static void Main(string[] args)
{
    // declare and initialize variables
    int a = 0;
    int b = 0;
    int area = 0;
    string read;
    bool isValid = false;

    while (!isValid) { 
        try
        {
            // Input data solicited
            Console.WriteLine("Rectangle height: ");
            read = Console.ReadLine();
            a = int.Parse(read);

            Console.WriteLine("Rectangle width: ");
            read = Console.ReadLine();
            b = int.Parse(read);

            //operation
            area = a * b;

            //print result
            Console.WriteLine("The area of the rectangle is: " + area + " cm²");
            isValid = true;
            
        }
        catch (Exception e)
        {
            Console.WriteLine("ERROR. Wrong data type, expected number.");
        }
    };
}
...

Using break

...
static void Main(string[] args)
{
    // declare and initialize variables
    int a = 0;
    int b = 0;
    int area = 0;
    string read;

    do { 
        try
        {
            ...
            break
            
        }
        catch (Exception e)
        {
            ...
        }
    } while (true);
}
...

Also, there was one error in a = int.Parse(line), there's no line var. Same with variable b.