Get parent & child relationship using Recursive in C#

var regex = new Regex(@"
\( # Match (
(
[^()]+ # all chars except ()
| (?\() # or if ( then Level += 1
| (?<-Level>\)) # or if ) then Level -= 1
)+ # Repeat (to go from inside to outside)
(?(Level)(?!)) # zero-width negative lookahead assertion
\) # Match )",

RegexOptions.IgnorePatternWhitespace);

foreach (Match c in regex.Matches(input))
{

Multiplestring1.Add(c.Value.Remove(c.Length - 1).Substring(1));

}

StringBuilder builder = new StringBuilder();

foreach (var safePrime in Multiplestring1)
{

// Append each int to the StringBuilder overload.
builder.Append(safePrime).AppendLine(Environment.NewLine);

}

result = builder.ToString();

Multiplestring2.Add(result.Split(new string[] { "\r\n"},StringSplitOptions.RemoveEmptyEntries));

Multiplestring1.RemoveAt(1);
Multiplestring1.RemoveAt(0);
GetNestedCheckedItems(result, level + 1, objparentclass);