using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"(?<=\{\{mecha.*?\}\})(?<!\{\{track.*?\}\})(\{\{track)";
string substitution = @"|tracks=$1";
string input = @"{{mecha|p=Neutron Stampeder}}{{track|p=Ignited}}{{track|p=Ignited}}
{{track|p=Mizu no Akashi}}
{{track|p=Mizu no Akashi}}";
RegexOptions options = RegexOptions.Multiline;
Regex regex = new Regex(pattern, options);
string result = regex.Replace(input, substitution);
}
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx