如何使用console.readline()读取整数？

Question

I'm a beginner who is learning .NET.

I tried parsing my integer in console readline but it shows a format exception.

My code:

using System;
namespace inputoutput
{
    class Program
    {        
        static void Main()
        {
            string firstname;
            string lastname;
         // int age = int.Parse(Console.ReadLine());
            int age = Convert.ToInt32(Console.ReadLine());
            firstname = Console.ReadLine();
            lastname=Console.ReadLine();
            Console.WriteLine("hello your firstname is {0} Your lastname is {1} Age: {2}",
                firstname, lastname, age);
        }
    }
}

Answer 1

If it's throwing a format exception then that means the input isn't able to be parsed as an int . You can check for this more effectively with something like int.TryParse() . For example:

int age = 0;
string ageInput = Console.ReadLine();
if (!int.TryParse(ageInput, out age))
{
    // Parsing failed, handle the error however you like
}
// If parsing failed, age will still be 0 here.
// If it succeeded, age will be the expected int value.

Answer 2

Your code is absolutely correct but your input may not be integer so you are getting the errors. Try to use the conversion code in try catch block or use int.TryParse instead.

Answer 3

You can handle invalid formats except integer like this;

        int age;
        string ageStr = Console.ReadLine();
        if (!int.TryParse(ageStr, out age))
        {
            Console.WriteLine("Please enter valid input for age ! ");
            return;
        }

Answer 4

Console.WriteLine("Enter number ");
int day = int.Parse(Console.ReadLine());

Answer 5

You can convert numeric input string to integer (your code is correct):

int age = Convert.ToInt32(Console.ReadLine());

If you would handle text input try this:

int.TryParse(Console.ReadLine(), out var age);