using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"(err\s*?\d{1})|[^\d]\s+(\d{3})(?:$|\s+(?!\d))";
string input = @"The below items should match:
-----------------------------
123
456 123
123 324 324
Match the number in this sentence 123 as well
999
The below items should NOT match:
---------------------------------
1234
12345
123456
1234567
£123
$456
Err404
ERR404
err404
Err 404
ERR 404
err 404
there is err 404 on page
this err 1232222222222 as well
a string 12323 like this
asd
4444333322221111
4444 3333 2222 1111
Err123
02012341234
920 1234 1234";
RegexOptions options = RegexOptions.Multiline | 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