Question

i want to count how many numbers from 0 to 9 is in string. tried some code but it don’t works, it returns 0 every time. whats wrong and how to fix? also if u can tell me how do it with srting.Count() method. thanks.

// Attempt 1
string str = textBox1.Text;
int b = 0;
int n = 0;
foreach (char a in str)
{
    if ((b > 0) && (b < 9))
    {
        if ((char)b == a)
            n++;
    }
}
label1.Text = n;

// Attempt 2
string str = textBox1.Text;
int n = 0;
foreach (char a in str)
{
    int[] k = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
    foreach (int b in k)
    {
        if (b == a)
            n += 1;
    }
}
label1.Text = n

Answer 1

Use a simple regex for that?

  var matches = System.Text.RegularExpressions.Regex.Matches("1 2 3 4 5 6 10 11 12", "(?<![0-9])[0-9](?![0-9])");
  Console.WriteLine(matches.Count);

Outputs 6. This picks up only the isolated digits, not the ones that are part of two or more digit numbers.

EDIT: I somehow completely missed the question tag being ‘c#’ and wrote my original answer in python. Conveniently the actual regex pattern syntax required is the same in both python and c#.