C# Program: Numeric and integer input validation

Last update on December 20 2024 12:40:20 (UTC/GMT +8 hours)

Write a C# program that prompts the user to input a numeric integer and throws an exception if the number is less than 0 or greater than 1000.

Sample Solution:

C# Sharp Code:

using System;

class Program {
  static void Main() {
    try {
      // Prompt user to input a numeric integer and read the input
      Console.Write("Input a numeric integer: ");
      int number = Convert.ToInt32(Console.ReadLine());

      // Call method to validate number range
      ValidateNumberRange(number);

      // Display valid input if no exception was thrown
      Console.WriteLine("Valid input: " + number);
    } catch (NumberOutOfRangeException ex) {
      // Catch block for handling NumberOutOfRangeException
      Console.WriteLine("Error: " + ex.Message);
    } catch (FormatException) {
      // Catch block for handling FormatException when non-numeric input is entered
      Console.WriteLine("Error: Invalid input. Please enter a numeric integer.");
    } catch (Exception ex) {
      // Catch block for handling other types of exceptions
      Console.WriteLine("An error occurred: " + ex.Message);
    }
  }

  // Method to validate if the number is within the specified range
  static void ValidateNumberRange(int number) {
    if (number < 0 || number > 1000) {
      // Throw NumberOutOfRangeException if the number is out of the specified range
      throw new NumberOutOfRangeException("Number out of range. Please enter a number between 0 and 1000.");
    }
  }
}

// Custom exception class for NumberOutOfRangeException
class NumberOutOfRangeException: Exception {
  public NumberOutOfRangeException(string message): base(message) {}
}

Sample Output:

Input a numeric integer: -1
Error: Number out of range. Please enter a number between 0 and 1000. 

 
Input a numeric integer: 1001
Error: Number out of range. Please enter a number between 0 and 1000.

  
Input a numeric integer: 0
Valid input: 0

  
Input a numeric integer: 1000
Valid input: 1000

  
Input a numeric integer: 666
Valid input: 666

Explanation:

In the above exercise,

• The Main() method prompts the user to input a numeric integer using Console.Write() and Console.ReadLine(). The input is converted to an int using Convert.ToInt32() and stored in the variable number.
• The ValidateNumberRange method is called with the number as an argument. This method checks if the number is less than 0 or greater than 1000. If it is, it throws a custom exception called NumberOutOfRangeException with the message "Number out of range. Please enter a number between 0 and 1000."
• In the Main method, the exceptions are handled using catch blocks. If a NumberOutOfRangeException is thrown by the ValidateNumberRange method, it is caught and the error message is displayed.
• If a FormatException occurs, the user entered a non-integer value. This exception is caught and an appropriate error message is displayed.
• Any other exceptions are caught by the generic catch block, and a general error message is displayed.

Flowchart:

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