How can I extract 5 digit numbers from a large string?

Question

I have used a timer to run through a string, I have used a while too but I am wondering is there a faster way. I have string that contains date serial number, the date is always after the text d|

private void Timer1_Tick(object sender, EventArgs e)
{
    string caldata = textBox6.Text;
    textBox7.Text = caldata.Length.ToString();

    if (caldata.Substring(0, 2) == "d|")
    {
        // MessageBox.Show("Found date" + caldata.Substring(2, 5));
        listBox1.Items.Add(caldata.Substring(2, 5));

        textBox6.Text = caldata.Remove(0, 7);
        caldata = textBox6.Text;
    }
    else
    {
        textBox6.Text = caldata.Remove(0, 1);
        caldata = textBox6.Text;
    }


    if (caldata.Length < 4)
    {
        timer1.Enabled = false;
    }
}

My string that contains the data looks like the attached.

Hard to see a question. You make it faster by not using a timer. — Hans Passant, Sep 20 '19 at 12:09
Please don't downvote, he is a new bee. Also what make you use timer? — Harshad Vekariya, Sep 20 '19 at 12:12
Possible duplicate of [Find and extract a number from a string](https://stackoverflow.com/questions/4734116/find-and-extract-a-number-from-a-string) — Liam, Sep 20 '19 at 12:15
To see if it is doing something ...lol ... I tried while but it looks like it hangs and takes minutes and then it responds so it takes to long to start doing its job — Oxley Pilot, Sep 20 '19 at 12:15
*My string that contains the data looks like the attached.* you seemed to of forgotten to finish this? — Liam, Sep 20 '19 at 12:16
@OxleyPilot where's the string? Post the question in the question itself. What are you searching for? Righ now people have to guess what you want from the code and a missing input string — Panagiotis Kanavos, Sep 20 '19 at 12:17

score 1 · Accepted Answer · edited Sep 20 '19 at 12:48

1

Generally, your problem could be solved with careful debugging and stepping through the code.

Anyway, below is my suggestion:

You could use regular expressions: (?<=d\|)\d{5}

Explanation:

(?<=d\|) - positive lookbeihnd: assert what preceds is d\|

\d{5} - match 5 digits

Code sample

  string caldata = "";
  MatchCollection matches = Regex.Matches(caldata, @"(?<=d\|)\d{5}");
  foreach (Match match in matches)
  {
    string txt = match.Value;
    // ... do smoething with text
  }

edited Sep 20 '19 at 12:48

Gönnhardt

13
3

answered Sep 20 '19 at 12:15

Michał Turczyn

32,028
14
47
69

Why the positive look behind? `\d{5}` should do it fine? – Liam Sep 20 '19 at 12:17
@Liam To assert what preceds is desired `d|`, then take (match) five numbers – Michał Turczyn Sep 20 '19 at 12:17
I've just seen the `d|` requirement! – Liam Sep 20 '19 at 12:19
Now I have learnt something, Finding the data is much faster, I was looking into regex now, but this has put me on the correct path. Thank you! – Oxley Pilot Sep 20 '19 at 12:34

Gönnhardt · Answer 2 · 2019-09-20T12:32:26.957

Remove and Substring are pretty slow string operations, if you want to extract data from a string you should try to find only that and not remove the irrelevant data around it.

Regex seems to be the way go here, in this case "(?!d\|)\d{5}" should be the fastest.

So your code would look like this:

var matches = Regex.Matches(caldata, @"(?!d\|)\d{5}");
foreach(Match m in matches)
{
  listbox1.Items.Add(m.Value);
}

How can I extract 5 digit numbers from a large string?

2 Answers2