字母v的正则表达式前加下划线…，后跟任意长度的数字

Question

I have a string like below

string a= "idh_abcdef_normal_verymuch_ext_v1_20131101000000";

How do I find the index of "_v1" (small letter v followed by a number ( of any length ).

Below code is not working :(

Console.WriteLine(System.Text.RegularExpressions.Regex.Match(a,"^[v][0-9]$").Index);

could someone help me please.

Answer 1

If you are sure that the string contains the given substring:

int index = Regex.Match(s, "_v\\d").Index;

otherwise

Match match = Regex.Match(s, "_v\\d");
if (match.Success)
    index = match.Index;

Answer 2

The problem with your regex:

^[v][0-9]$

Is that you are using a pattern to start with v and finish with a number. So, only strings like v0 , v2 ... v9 are valid. Btw, you don't need to use [v] since it's exactly the same as v .

You can use a regex look ahead like this:

_v(?=\d)

Working demo

Or a simple regex

_v\d

Working demo

Answer 3

Use:

_v\d+

As the regex you need.

Answer 4

Why not a simple search:

string searchString = "_v1_";
int index = a.IndexOf(searchString);
string sNumber = a.Substring(index + searchString.Length);
long lNumber = long.Parse(sNumber);