初学者使用C＃验证数字和字母

Question

I'm new to C# and can't figure out how to validate within the code I already wrote. I have the code working perfect, but want to keep adding features. I'm looking for tips or anything you care to mention. Thanks ahead of time. Here is the code I have so far and need validation on the 3 getInputs near the green comments.

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

namespace BasicUserInterface
{
    class Program
    {
        static void DisplayApplicationInformation()
        {
            Console.WriteLine("Welcome to the Basic User Interface Program");
            Console.WriteLine("CIS247, Week 2 Lab");
            Console.WriteLine("Name: Fred Ziyad");
            Console.WriteLine();
            Console.WriteLine("This program accepts user input as a string, then makes the");
            Console.WriteLine("approppriate data conversion and display the results.");
            Console.WriteLine();
        }

        static void DisplayDivider(String outputTitle)
        {
            Console.WriteLine("************* " + outputTitle + " **************");
        }

        static string GetInput(string inputType)
        {
            string strInput;

            Console.Write("Enter " + inputType + ": ");
            strInput = Console.ReadLine();

            return strInput;
        }

        static void TerminateApplication()
        {
            Console.WriteLine();
            Console.WriteLine("Thank you for using the Basic User Interface program");
            Console.Read();
        }

        static void Main(string[] args)
        {
            int age;
            double mileage;
            string strInput, name;

            DisplayApplicationInformation();

            DisplayDivider("Start Program");
            Console.WriteLine();

            DisplayDivider("Get Name");
            name = GetInput("your name");
            Console.WriteLine("Your name is " + name);
            Console.WriteLine();
            //Validate name to be a string of letters.

            DisplayDivider("Get Age");
            strInput = GetInput("your age");
            age = int.Parse(strInput);
            Console.WriteLine("Your age is: " + age);
            Console.WriteLine();
            //Validate age to be a number.

            DisplayDivider("Get Mileage");
            strInput = GetInput("gas mileage");
            mileage = double.Parse(strInput);
            Console.WriteLine("Your car MPT is: " + mileage);
            //Validate mileage to be a number.

            TerminateApplication();
        }
    }
}

Answer 1

The numeric types have a TryParse method that you can use to catch illegal input.

Example:

DisplayDivider("Get Age");
strInput = GetInput("your age");
if (int.TryParse(strInput, out age)) {
  Console.WriteLine("Your age is: " + age);
  Console.WriteLine();
} else {
  Console.WriteLine("Age input was not a valid number.");
}

Answer 2

//Validate age to be a number.

Here's how you validate whether a string is a number:

string str = "123";
int result;
if (!Int32.TryParse(str, out result))
    ; //not a whole number

TryParse will return false if the string doesn't successfully parse out as a valid integer, and, if it does parse successfully, will return the converted int in the out parameter.

Or if you want to allow decimals:

string str = "123.5";
double result;
if (!Double.TryParse(str, out result))
    ; //not a number

Same idea

---

//Validate name to be a string of letters.

Here's how you count the number of characters in a string that are not letters :

string str = "AB3C";
int numberOfNonLetters = str.Count(c => !Char.IsLetter(c));

To make sure a string has only letters, just make sure numberOfNonLetters is zero