How to prevent non-numeric input in VB.NET?

I'm working on a program that requires the user to input an integer. How do I prevent the user from enter开发者_JAVA百科ing a non-numeric value? I tried using the IsNumeric() function but I get an error before I can use it. I get the error at the console.read, before I can call the IsNumeric() function. Here is my code:

Dim num As Integer

    Console.Write("enter num:")
    num = Console.ReadLine 

    If IsNumeric(num) = True Then
        Console.WriteLine("valid. num = " & num)
    Else
        Console.WriteLine("invalid")
    End If

Any help is greatly appreciated.

---

Try this:

Dim num As Integer

Console.Write("enter num:")
Dim input = Console.ReadLine

If Integer.TryParse(input, num) Then
    Console.WriteLine("valid. num = " & num)
Else
    Console.WriteLine("invalid")
End If

---

This is exactly the situation that Integer.TryParse() is designed for. TryParse will return false if the string you test can't be converted into an integer.

---

Rather try something like:

Dim num as Integer
Console.Write("Enter num: ")

While (Not (Integer.TryParse(num, Console.ReadLine())))
    Console.WriteLine("Please enter an Integer only: ")
End While

The TryParse method tries to parse the input value and returns a false when the value couldn't be parsed to the said type. The above code will ask the used for input until they enter an integer.

---

You could read a string, then attempt to convert it into the integer. Trap any exceptions produced by the conversion, to handle non-numeric input.

---

In C# sorry...

using System;
    class Program
    {
        static void Main(string[] args)
        {
            int a = GetNumericInput();
            Console.WriteLine("Success, number {0} entered!",a);
            Console.Read();
        }

        private static int GetNumericInput()
        {
            int number;
            string input;
            bool first = true;
            do
            {
                if (!first)
                {
                    Console.WriteLine("Invalid Number, try again");
                }
                Console.WriteLine("enter a number");
                input = Console.ReadLine();
                first = false;
            } while (!int.TryParse(input, out number));
            return number;
        }
    }