using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"(^[^:\n]+:).*(\n\1.*)*";
string input = @"Subject: this is text not to be matched
Subject2: this is text to be recognized.
Subject2: This text can be different.
Subject2: ..and this text will be also matched in the first match.
Subject3: This text alone.
this text will not be matched
Subject2: New start of a new match.
Subject2: continuation of the above line";
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