How can I validate console input as integers?

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I have written my codes and i want to validate it in such a way thet it will only allow intergers to be inputed and not alphabets. Here is the code, please I will love you to help me. Thanks.

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

namespace minimum
    class Program
        static void Main(string[] args)
            int a = Convert.ToInt32(Console.ReadLine());
            int b = Convert.ToInt32(Console.ReadLine());
            int c = Convert.ToInt32(Console.ReadLine());

            if (a < b)
                if (a < c)
                    Console.WriteLine(a + "is the minimum number");
            if (b < a)
                if (b < c)
                    Console.WriteLine(b + "is the minimum number");
            if (c < a)
                if (c < b)
                    Console.WriteLine(c + "is the minimum number");


You should test if it's an int instead of converting in right away. Try something like :

string line = Console.ReadLine();
int value;
if (int.TryParse(line, out value))
   // this is an int
   // do you minimum number check here
   // this is not an int

Validation Controls In ASP.NET, Displays a report of all validation errors occurred in a Web page Simply call Readline() and loop with Int.TryParse until the user inputs a valid number :) To get the console to filter out alphabetical keystrokes you have to take over input parsing. The Console.ReadKey() method is fundamental to this, it lets you sniff the pressed key.

Simply call Readline() and loop with Int.TryParse until the user inputs a valid number :)

int X;

String Result = Console.ReadLine();

while(!Int32.TryParse(Result, out X))
   Console.WriteLine("Not a valid number, try again.");

   Result = Console.ReadLine();

Hope that helps

C#, whether the specified string at specified position matches with any number or not. If it matches then it returns True otherwise returns False. If it can't, it returns false. Solutions using the int.Parse(someString) alternative shown in other responses works, but it is much slower because throwing exceptions is very expensive. If you want to accept decimal numbers, the decimal class also has a .TryParse() method. Replace int with decimal in above, and the same principles apply.

To get the console to filter out alphabetical keystrokes you have to take over input parsing. The Console.ReadKey() method is fundamental to this, it lets you sniff the pressed key. Here's a sample implementation:

    static string ReadNumber() {
        var buf = new StringBuilder();
        for (; ; ) {
            var key = Console.ReadKey(true);
            if (key.Key == ConsoleKey.Enter && buf.Length > 0) {
                return buf.ToString() ;
            else if (key.Key == ConsoleKey.Backspace && buf.Length > 0) {
                buf.Remove(buf.Length-1, 1);
                Console.Write("\b \b");
            else if ("0123456789.-".Contains(key.KeyChar)) {
            else {

You could add, say, Decimal.TryParse() in the if() statement that detects the Enter key to verify that the entered string is still a valid number. That way you can reject input like "1-2".

Console.Read() Method in C#, the next character from the standard input stream. This method basically blocks its return when the user types some input characters. As soon as the user press ENTER key it terminates. Reading integers from files is a very different matter. Raúl Roa's approach can be good for that if properly worked out. I also suggest that wrong input files should not be tolerated, but it really depends on the application. Be warned that using >> and getline() in the same program on cin will lead to some problems. Use one of them only, or

Do not Convert the input from the user immediately. Put it in a string and use Int32.TryParse(...) to find out whether or not a number was entered. Like this:

int i;
string input = Console.ReadLine();
if(Int32.TryParse(input, out i))
    // it is a number and it is stored in i
    // it is not a number

Input Validations in C# at C Sharp for Beginners Course Codeasy.Net, Now I need an input validation system; otherwise, if I expect an int but receive a string, Console.WriteLine("Input your name"); var name = Console.ReadLine()​  I have a piece of code where I ask the user to input a number as an answer to my question. I can do to_i but tricky/garbage inputs would escape through to_i. For example, if a user inputs 693iirum5 as an answer then #to_i would strip it to 693. Please suggest a function, not a regular expression. Thanks in advance for replying.

Note that

if (a < b) {
    if (a < c) {

is equivalent to

if (a < b && a < c) {

and that this latter form introduces less nesting and is more readable, particularly if your code grows more complex. Also, you should probably never use Convert.ToInt32 - it has a particularly ill-conceived and surprising corner case; and it's also less type-safe than int.Parse which is the superior choice where possible - or int.TryParse when you're unsure whether the string is valid. Basically, avoid Convert.... wherever possible.

Validating integer or string input, I'm at uni and working on an assignment in c# that takes some user input (from they keyboard via console). The input validation required: numbers must be within  It would be better you use the method Double.TryParse.This way you will check if the string that user provided can be parsed to a double. // This is the variable, in which will be stored the temperature. double temperature; // Ask the user input the temperature. Console.WriteLine("Please enter the temperature in Celsius: "); // If the given temperature hasn't the right format, // ask the user

How to verify if user input is a number in C#, In the console you can do something like, if you are looking for an integer (whole number): [code]bool Valid = False; int Number; while(Valid == False){ string  You can convert the string to integer using Convert.ToInt32 () function. int intTemp = Convert.ToInt32(Console.ReadLine()); improve this answer. edited Sep 1 '15 at 12:48. 16 silver badges. 28 bronze badges. answered Jun 27 '14 at 4:15. 12 silver badges. 13 bronze badges. Amazing, I tried this before and it didn't work. But just tried it again

C# Console.ReadLine Example (While Loop), Console.ReadLine. This reads input from the console. When the user presses enter, ReadLine(); // Get string from user if (line == "exit") // Check string { break; } Next: This program tries to multiply an integer value received by the user by 10  I have to write a simple console application that counts how many coins are required to make up a particular number given by the user. My question is how do I check that the input giving by the user is a valid integer before I convert the string (Num) to an Integer (i).

C# Sharp exercises: Check if an integer is in the range -10 to 10 , Tasks; public class Exercise36 { static void Main(string[] args) { Console.Write("​Input a first number: "); int m = Convert.ToInt32(Console. Validate That Input Contains Only Integers. The result of dividing two random integers can result in an integer or a number with a fractional part

  • +1 But you should probably validate for modifiers :-) (Ctrl, Alt...)
  • That's true. Let's call it a feature :)
  • WOW is that a record having all these solutions thrown in at the same time? Should we delete them?
  • The code? a puzzle? hmm, that's not good :-) - I intended to make the functionality compositional and avoid large functions - I suppose the generate function takes a little getting used to...