string input = @"string error_message= ""{\""2705\"":\""Error importing username:3167763, primary email: pkumar194@google.com, error: User already exists but Email does not match: pkumar194@googlee.com vs pkumar193@google.co.in\"",\""10001\"":\""Error importing username:3195330, primary email: alejandra.mejia@google.com, error: User already exists but Email does not match: alejandra.mejia@google.com vs alejandra.mejia@googlee.com\""}"";";
var collection = Regex.Matches(input, pattern)
.Cast<Match>()
.Select(match =>
new {username = int.Parse(match.Groups[1].Value), primary_email = match.Groups[2].Value}