I have a Windows program that prompts the user to input a file path, and file name. I then check that the file exists with Directory.Exists.

  Then the user inputs a filename. I check it using this answer to check whether the filename is valid or not(it may or may not yet exist).

Here is my code:

I need to make sure that

• The filepath exists
• The filename is valid
• That filename + filepath <= 260 (this is max char limit on windows)
• That my program doesn't crash while doing this

I have a Windows program that prompts the user to input a file path and filename. I then check that the file exists with Directory.Exists. Then the user inputs a filename and I check it using this answer to check whether the filename is valid or not  (it may or may not yet exist).

I need to make sure that:

• The filepath exists
• The filename is valid
• That filename + filepath <= 260 (this is max char limit on Windows)
• That my program doesn't crash while doing this

using System;
using System.IO;
using System.Text.RegularExpressions;

public static string GetFilePath()
{
    string filePath = " ";
    bool directoryFound = true;
    do
    {
        if (!directoryFound)
        {
            Console.WriteLine("This directory not found:\n{0}\nPlease double check file path. \nPlease Double check that this program has read and write access to the directory.\n", filePath);
        }

        Console.WriteLine("Please specify file location:");
        filePath = @Console.ReadLine(); 
        Console.Clear();

        directoryFound = Directory.Exists(filePath);
        if (filePath.Length >= 240) //This looks like a bad solution
        {
            directoryFound = false;
            Console.WriteLine("Please keep the filepath under 240 chars so that you still are able to provide a name for the file.");
        }

    } while (!directoryFound);

    filePath = GetFileName(filePath);

    return filePath ;
}
    
    public static string GetFileName(string filePath)
    {
        string fileName = " ";
        bool isValidName = true;
        int fileNameMaxLength = 0;
        do
        {
            if (!isValidName)
            {
                
                Console.WriteLine("{0} \nis not a valid filename. Make sure you enter a valid filename.\nYour max filename length should be {1}", fileName, fileNameMaxLength);
            }

            Console.WriteLine("Please enter the name of the file:");
            fileName = Console.ReadLine();
            Console.Clear();

            string illegalChars = @"^(?!^(PRN|AUX|CLOCK\$|NUL|CON|COM\d|LPT\d|\..*)(\..+)?$)[^\x00-\x1f\\?*:\"";|/]+$";

            isValidName = Regex.IsMatch(fileName, illegalChars, RegexOptions.CultureInvariant);

            if (fileName.Length + filePath.Length > 254)
            {
                isValidName = false;
                fileNameMaxLength = 254 - filePath.Length;
            }

        } while (!isValidName);
        return Path.Combine(filePath, (fileName + ".ppm"));
    }

}

using System;
using System.IO;
using System.Text.RegularExpressions;

public static string GetFilePath()
{
    string filePath = " ";
    bool directoryFound = true;
    do
    {
        if (!directoryFound)
        {
            Console.WriteLine("This directory not found:\n{0}\nPlease double check file path. \nPlease Double check that this program has read and write access to the directory.\n", filePath);
        }

        Console.WriteLine("Please specify file location:");
        filePath = @Console.ReadLine(); 
        Console.Clear();

        directoryFound = Directory.Exists(filePath);
        if (filePath.Length >= 240) //This looks like a bad solution
        {
            directoryFound = false;
            Console.WriteLine("Please keep the filepath under 240 chars so that you still are able to provide a name for the file.");
        }

    } while (!directoryFound);

    filePath = GetFileName(filePath);

    return filePath ;
}
    
    public static string GetFileName(string filePath)
    {
        string fileName = " ";
        bool isValidName = true;
        int fileNameMaxLength = 0;
        do
        {
            if (!isValidName)
            {
                
                Console.WriteLine("{0} \nis not a valid filename. Make sure you enter a valid filename.\nYour max filename length should be {1}", fileName, fileNameMaxLength);
            }

            Console.WriteLine("Please enter the name of the file:");
            fileName = Console.ReadLine();
            Console.Clear();

            string illegalChars = @"^(?!^(PRN|AUX|CLOCK\$|NUL|CON|COM\d|LPT\d|\..*)(\..+)?$)[^\x00-\x1f\\?*:\"";|/]+$";

            isValidName = Regex.IsMatch(fileName, illegalChars, RegexOptions.CultureInvariant);

            if (fileName.Length + filePath.Length > 254) //254 instead of 260 in order to account for file extension
            {
                isValidName = false;
                fileNameMaxLength = 254 - filePath.Length;
            }

        } while (!isValidName);
        return Path.Combine(filePath, (fileName + ".ppm"));
    }

}