How to get predecessor id from task predecessor string?

I'm working on MPXJ library. I want to get predecessors id from below string. It's complex for me. Please help me get all predecessors id. Thanks.

Task predecessor string:

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]]]

I need get the predecessors id: 10, 11, 9

Pattern:

[Task id=12 uniqueID=145 name=Alibaba1] -> [Task id=10 uniqueID=143 name=Alibaba2]]

Solution

To grab those ID's you need to look for the Task id after -> You can try the following using Matches method.

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

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

Working Demo

Explanation:

->          # '->'
\s*         # whitespace (\n, \r, \t, \f, and " ") (0 or more times)
\[          # '['
 Task       # 'Task'
 \s*        # whitespace (\n, \r, \t, \f, and " ") (0 or more times)
 id=        # 'id='
  (         # group and capture to \1:
   \d+      #   digits (0-9) (1 or more times)
  )         # end of \1