using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"(?<=<a>)(\s*?<b>([^<]+)<\/b>)(\s*?<b>([^<]+)<\/b>)?(\s*?<b>([^<]+)<\/b>)?(\s*?<b>([^<]+)<\/b>)?";
string input = @"<a>
<b>test11</b>
</a>
<a>
<b>test21</b>
<b>test22</b>
</a>
<a>
<b>test31</b>
<b>test32</b>
<b>test33</b>
</a>
<a>
<b>test41</b>
<b>test42</b>
<b>test43</b>
<b>test44</b>
</a>
<c>
<b>test51</b>
<b>test52</b>
</c>";
RegexOptions options = RegexOptions.Multiline;
foreach (Match m in Regex.Matches(input, pattern, options))
{
Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index);
}
}
}
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