CODEWITHSUNDEEP
c#regexstringdigits
toosweetnitemare
toosweetnitemare

Reputation: 2276

C# string starts with a number regex

I've been searching around for a little while to figure out how to confirm a string begins with a number. I came across a regex statement '/^\d/' which I can confirm says if starts with digit. However I can not seem to get it to work in the code below. Where did I went wrong in the statement if(Regex.Match(info,"/^\d/"))?

//String attachbody is the attachment body from an email C read into a string
string[] data = Regex.Split(attachbody, "\n");

foreach (String info in data)
{
    if (Regex.Match(info,"/^\d/"))
    {
        string[] tabbedHeaderData = Regex.Split(info, "\t");
        TicketID = tabbedHeaderData[0].ToString();
        Status = tabbedHeaderData[1].ToString();
        URL = tabbedHeaderData[2].ToString();
        InitCats = tabbedHeaderData[3].ToString();
        PostRevCats = tabbedHeaderData[4].ToString();
        ListNumClosed = tabbedHeaderData[5].ToString();

        Console.WriteLine(TicketID);
        Console.WriteLine(Status);
        Console.WriteLine(URL);
        Console.WriteLine(InitCats);
        Console.WriteLine(PostRevCats);
        Console.WriteLine(ListNumClosed);
        Console.ReadLine();
    }
}

example data (tab delimited):
TicketID Status URL InitCats PostRevCats ListNumClosed 555555 Closed http://5555555.com/searcho Malicious Sites 55555

Upvotes: 32

Views: 67722

Answers (6)

Nainesh Patel
Nainesh Patel

Reputation: 588

If you do not want to use Regex (some inteview question platforms do not allow regex ) and Char.IsDigit(info[0]),

You can use if(info[0] => 0 && info[9] <= 9) to check if char is numeric or not.

Depends on requirements if you do not want to consider '.' as Digit (for e.g. Integer values only) do not use Char.IsDigit(info[0]) since this function returns true for '.'

Upvotes: 0

agent-j
agent-j

Reputation: 27913

You don't need a regex for this. Try

if (info.Length > 0 && char.IsDigit(info[0]))
{
   ...
}

If you want to use the regex, take out the // so it's just Regex.IsMatch(info,@"^\d").

Upvotes: 44

Yogurt The Wise
Yogurt The Wise

Reputation: 4489

If your only trying to find out if the string begins with a number. Like above, you canskip using regex. Just use Substring, remove the first character and test if it is a number.

Now if your trying to remove the entire number, then I would convert the string to a char array, and test the chars.

pseudo string s = "" for each c in chars{ if c is number then s += c else exit for } convert the s to an integer, you got the number at the begining of the string.

Upvotes: 0

erlando
erlando

Reputation: 6756

Your regex is wrong. .Net doesn't use perl-style regexs. The correct expression is @"^\d".

And you should use Regex.IsMatch(...) if you're not going to use the MatchCollection from .Match for anything:

RegEx.IsMatch(info, @"^\d")

Upvotes: 1

Darin Dimitrov
Darin Dimitrov

Reputation: 1038720

Your regex is wrong. /.../ is javascript convention for defining regular expressions. Try like this in C#:

if (Regex.IsMatch(info, @"^\d"))

Also notice that you should use the IsMatch method which returns boolean or your code won't even compile.

And if you wanted to match that the string starts with one or more digits:

if (Regex.IsMatch(info, @"^\d+"))

Upvotes: 76

Alistair Evans
Alistair Evans

Reputation: 36473

It's the format of the string that you've supplied to Regex.Match.

The correct format would be:

Regex.Match(info,@"^\d")

The @ means that escape characters (like the backward slash) are treated as normal characters. Without it your regex would need to be "^\\d".

Upvotes: 4

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