using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"(?:(?<= [+][1-9])|(?<= [1-9])|(?<= ))([2-9][0-9]{9})\b";
string input = @"abcd +12125551212 xyz should match starting at 212
abcd +2125551212 xyz should NOT match (+ sign only)
abcd 2125551212 xyz match OK!
abcd+12125551212 xyz should NOT match (no white space at start)
abcd 12125551212 xyz should match starting at 212
";
RegexOptions options = RegexOptions.IgnoreCase;
foreach (Match m in Regex.Matches(input, pattern, options))
{
Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index);
}
}
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx