using System;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{

          
String input = @"Task Predecessors:[[Relation [Task id=12 uniqueID=145 name=Alibaba1] -> [Task id=10 uniqueID=143 name=Alibaba2]], [Relation [Task id=12 uniqueID=145 name=Alibaba3] -> [Task id=11 uniqueID=144 name=Alibaba4]], [Relation [Task id=12 uniqueID=145 name=Alibaba5] -> [Task id=9 uniqueID=142 name=Alibaba6]]]";

Regex rgx = new Regex(@"(?i)->\s*\[Task\s*id=(\d+)");

foreach (Match m in rgx.Matches(input))
         Console.WriteLine(m.Groups[1].Value);
         
	}
}