using System;

using System.Text.RegularExpressions;

​

namespace Rextester{

    public class Program{

        public static void Main(string[] args){

            // Create a regex pattern to match 25 lines with various newline characters

        string pattern = @"^(.*(\r\n|\n|\r)){25}.*$";

        Regex regex = new Regex(pattern);

​

        // Test string containing 25 lines with various newline characters

        string testString = @"y|S1|12345678-12| 3UM ||

y|S2|12345678-12| 3UM ||

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​

        // Test the regex pattern

        bool isMatch = regex.IsMatch(testString);

        Console.WriteLine(isMatch); // Output: true if there are exactly 25 lines

        }

    }

}