I have simple function checking if string is number or not. Suddenly I discovered that it don't work with "0" or "00". Tell me why, please! And how to make it works?

string num = "00";
Int32.TryParse(num, out int n);
if (n > 0) return true; // It works nice on any digits except 0 and 00.

Also I tried:

double.TryParse(num, out double n);

But don't work too.

So I went in such way:

if ((n > 0) | (num == "0") | (num == "00")) return true;

CodePudding user response：

Of course 0 is not greater than 0, what did you expect? :)

int.TryParse returns a boolean letting you know if parsing the number was successful:

Returns

Boolean

true if s was converted successfully; otherwise, false.

So what you oughta do is the following:

return int.TryParse(num, out int _);

CodePudding user response：

You can create a function and call it to check if it is a number or not.

class Program
{
    static void Main(string[] args)
    {
        string num = "00";
        if (IsNumber(num))
            Console.WriteLine($"'{num}' is a number");
        else
            Console.WriteLine($"'{num}' is not a number");
    }

    private static bool IsNumber(string num)
    {
        return int.TryParse(num, out _);
    }
}