how to protect my program from input user of 01 instead 1

Question

i have a integer input that the user supposed to enter. how can i protect my program from input of 01 instead of 1. my input is integer !

choice = int.Parse(Console.ReadLine());       
if (choice < 1 || choice > 3)
{
    v = true;
    Console.WriteLine("Please enter number between 1 - 3: ");
}

check the length, since it should always be 1, or compare to an array of valid input such as [1,2,3] — Josh Adams, Jan 08 '19 at 14:13
only 01 or anything that starts a zero like: 012, or 0123, 00001 ? — styx, Jan 08 '19 at 14:14
For *numbers* it doesn't matter what input was, only the parsed value matter. Are you trying to do masked input (e.g. phone number) or numbers? — Sinatr, Jan 08 '19 at 14:14
i tried to make sure the user entered only numbers between 1-3 and not 01 or 02 or 03 because now the program accepted this issue — Shahar Dvora, Jan 08 '19 at 14:16
What's wrong with 01? How can it cause an issue since it's converted into a numeric value? — Cid, Jan 08 '19 at 14:18
As soon as you `int.Parse()` you lose the ability to do what you're trying to do. Don't convert it - just leave it as a string. Once you've validated it then you can convert it and do whatever you want. Also, `Console.ReadKey()` might be more suitable since that will only allow 1 character and not wait for enter to be pressed. — Reinstate Monica Cellio, Jan 08 '19 at 14:18
If user prompted to enter number, he can enter `01` or `+00000000001`. Both should be *OK* if you allow number `1`. Because after parsing both will be `1`. — Sinatr, Jan 08 '19 at 14:20
and if the input is integer can i do something else to solve that. — Shahar Dvora, Jan 08 '19 at 14:22
Solve what? You get input as `string` (this is what `Console.ReadLine()` returns), don't parse that to `int`. For a single number the value of string `Length` has to be 1, and this character (use indexer to get `char` from `string`) [IsNumber()](https://learn.microsoft.com/en-us/dotnet/api/system.char.isnumber?view=netframework-4.7.2) should return `true`. Of if you want character from `'1'` to `'2'`, then stick to `char` in your `if`. — Sinatr, Jan 08 '19 at 14:28
You can [hide input](https://stackoverflow.com/q/23433980/1997232). — Sinatr, Jan 08 '19 at 14:29
@Sinatr my input is integer because of that i used - int.Parse and if i change the input to string it will affect on other things. — Shahar Dvora, Jan 08 '19 at 14:34

score 0 · Answer 1 · answered Jan 08 '19 at 14:36

If you really want to prevent the user inputting 01, etc, you can just evaluate the string.

switch(Console.ReadLine()) {
    case "1": //do something
        break;
    case "2": //do something else 
        break;
    case "3": //do a third thing
        break;
    default: 
        v = true;
        Console.WriteLine("Please enter number between 1 - 3: ");
        break;
}

But as others already said in the comments, it shouldn't really matter if the user puts 01 instead of 1.

how to protect my program from input user of 01 instead 1

1 Answers1