title: c# how do i ask the user to press any keys to exit when they enter an invalid input
body: <p>I don't know how to ask user to press any keys to exit when they enter an invalid input.</p>
  
  <p>Whenever i try to put <code>Console.ReadKey</code>(), the program just keeps on going. I don't know how to make it stop when user did not put a valid input.</p>
  
  <p>Here's a screenshot
  <a href="https://i.stack.imgur.com/lShop.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/lShop.png" alt="enter image description here"></a></p>
  
  <p>Here's the code</p>
  
  <pre><code> /* Variable */
  
          int height = 0;                // stores user's height input
          int weight = 0;               // stores user's weight input
          const int factorBMI = 703;        // stores user's constant bmi which is 703
          double bmi = 0.0;                // stores user's calculated bmi
          /* User's Input */
          Console.WriteLine("************************************************************************************************************************");
          Console.WriteLine(" Please enter the person's height in inches:");                                         // Ask user to enter their height in inches
          if (Int32.TryParse(Console.ReadLine(), out height))
              Convert.ToDecimal(height);
          if (height &gt; 120)                                                                                        // Print an error message stating that if user's input is over 120 then an error pops
              Console.Write("\n height should be less than 120 inches, please press any key to exit:");
          if (height &lt; 5)                                                                                          // Print an error message stating that if user's input is less than 5 then an error pops
              Console.Write("\n height should be greater than 5 inches and if you entered a letter, \n please enter a number next time:\n");
          Console.WriteLine("\n Please enter the person's weight pounds:");                                       // Ask user to enter their weight in pounds
          if (Int32.TryParse(Console.ReadLine(), out weight))
              Convert.ToDecimal(weight);
          if (weight &gt;= 999)                                                                                     // Print an error message if the user's input is more than 999 lbs
              Console.Write("\n weight should be less than 999 pounds, please exit the application");
          if (weight &lt;= 0.5)                                                                                    // Print an error message if the user's input is less than 0.5 lbs
              Console.Write("\n weight should be greater than 0.5, \n if you did not enter a number, please enter a number next time:\n");
  
          /* Processing */
  
          bmi = Math.Round(weight / Math.Pow(height, 2) * factorBMI, 1);                                         // Calculates the user's BMI based on their height and weight input
  
          /* Output */
          Console.WriteLine("************************************************************************************************************************");
          Console.WriteLine("\n the BMI for a " + height + "\" tall person who weighs: " + weight + "lb. is " + bmi); // Print user's height, weight and calculated BMI
          if (bmi &lt; 16)                                                                                              // If BMI is less than 16 then print the message
              Console.WriteLine("\n base on your BMI you are severly underweight");
          else if (bmi &lt;= 18)                                                                                        // If BMI is less than 18 then print the message
              Console.WriteLine("\n base on your BMI you are underweight");
          else if (bmi &lt;= 25)                                                                                       // If BMI is less than 25 then print the message
              Console.WriteLine("\n base on your BMI you are healthy");
          else if (bmi &lt;= 30)                                                                                      // If BMI is less than 30 then print the message
              Console.WriteLine("\n base on your BMI you are overweight");
          else if (bmi &gt; 30)                                                                                      // If BMI is more than 30 then print the message
              Console.WriteLine("\n base on your BMI you are obese");
  
          /* Exit  */
  
          Console.WriteLine("\n\n Thanks for using our program, you may now exit this program by presing any key:");// Print message telling the user to press any keys to exit application
          Console.ReadKey();
  </code></pre>