using System;
using System.Text.RegularExpressions;
 
public class Test
{
public static void Main()
{
string str = "abc=0;def=2;abc=1;ghi=4;jkl=2";
Regex rgx = new Regex(@"(?<=abc=)\d+");
 foreach (Match m in rgx.Matches(str))
Console.WriteLine(m.Value);
}
}