using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"(<xref>[^\d]+)(\d)(<\/xref)";
string substitution = @"$1eqvalue$2$3";
string input = @"This is a example string and first line with <xref>id1</xref>then,<xref>id2</xref>and with no line breaks<xref>id3</xref>. This is a second line which has <xref>id4</xref>";
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