c#
    // Helper function to convert text inside double quotes to lowercase
    private static string ConvertToLowerCaseInsideQuotes(string text)
    {
        int startQuoteIndex = text.IndexOf('"');
        int endQuoteIndex = text.LastIndexOf('"');
        if (startQuoteIndex >= 0 && endQuoteIndex >= 0 && startQuoteIndex < endQuoteIndex)
        {
            string insideQuotes = text.Substring(startQuoteIndex, endQuoteIndex - startQuoteIndex + 1);
            string lowercaseInsideQuotes = insideQuotes.ToLower();
            return text.Substring(0, startQuoteIndex) + lowercaseInsideQuotes + text.Substring(endQuoteIndex + 1);
        }
        return text;
    }
}

c#
    // Helper function to convert text inside double quotes to lowercase
    private static string ConvertToLowerCaseInsideQuotes(string text)
    {
        int startQuoteIndex = text.IndexOf('"');
        int endQuoteIndex = text.LastIndexOf('"');
        if (startQuoteIndex >= 0 && endQuoteIndex >= 0 && startQuoteIndex < endQuoteIndex)
        {
            string insideQuotes = text.Substring(startQuoteIndex, endQuoteIndex - startQuoteIndex + 1);
            string lowercaseInsideQuotes = insideQuotes.ToLower();
            return text.Substring(0, startQuoteIndex) + lowercaseInsideQuotes + text.Substring(endQuoteIndex + 1);
        }
        return text;
    }
}

c#
using System;
using System.IO;

class Program
{
    static void Main(string[] args)
    {
        // Define the input and output file paths
        string inputFile = "input.txt";
        string outputFile = "output.txt";

        // Read the input file
        string[] lines = File.ReadAllLines(inputFile);

        // Process and write to the output file
        using (StreamWriter writer = new StreamWriter(outputFile))
        {
            foreach (string line in lines)
            {
                // Split the line based on the first occurrence of a double quote
                int firstQuoteIndex = line.IndexOf('"');
                if (firstQuoteIndex >= 0)
                {
                    string firstPart = line.Substring(0, firstQuoteIndex);
                    string secondPart = line.Substring(firstQuoteIndex);
                    
                    // Convert the second part (inside double quotes) to lowercase
                    string modifiedSecondPart = ConvertToLowerCaseInsideQuotes(secondPart);

                    // Combine the first part and the modified second part
                    string modifiedLine = firstPart + modifiedSecondPart;

                    // Write the modified line to the output file
                    writer.WriteLine(modifiedLine);
                }
                else
                {
                    // If there's no double quote, write the line as is
                    writer.WriteLine(line);
                }
            }
        }

        Console.WriteLine("Conversion completed. Check the output file for the result.");

    }

c#
using System;
using System.IO;

class Program
{
    static void Main(string[] args)
    {
        // Define the input and output file paths
        string inputFile = "input.txt";
        string outputFile = "output.txt";

        // Read the input file
        string[] lines = File.ReadAllLines(inputFile);

        // Process and write to the output file
        using (StreamWriter writer = new StreamWriter(outputFile))
        {
            foreach (string line in lines)
            {
                // Split the line based on the first occurrence of a double quote
                int firstQuoteIndex = line.IndexOf('"');
                if (firstQuoteIndex >= 0)
                {
                    string firstPart = line.Substring(0, firstQuoteIndex);
                    string secondPart = line.Substring(firstQuoteIndex);
                    
                    // Convert the second part (inside double quotes) to lowercase
                    string modifiedSecondPart = ConvertToLowerCaseInsideQuotes(secondPart);

                    // Combine the first part and the modified second part
                    string modifiedLine = firstPart + modifiedSecondPart;

                    // Write the modified line to the output file
                    writer.WriteLine(modifiedLine);
                }
                else
                {
                    // If there's no double quote, write the line as is
                    writer.WriteLine(line);
                }
            }
        }

        Console.WriteLine("Conversion completed. Check the output file for the result.");

    }