StreamReader read CRLF

Question

I'm working on validating some files from our customers who have to meet a specific file format. Each line has multiple fixed length fields and ends at 511 characters with characters 512 and 513 being CR and LF.

I've been able to use a substring to get each field easily enough, but I'm having an issue with StreamReader/ReadLine locating the 512th and 513th characters. When trying to use a substring to locate those characters, I'm getting the "System.ArgumentOutofRangeException" error.

StreamReader file = new StreamReader(textBox2.Text);
while ((line = file.ReadLine()) != null)
{
    int lineLength = line.Length;
    string crlf = "";
    /*
    if (lineLength == 511)
    {
        crlf = line.Substring(511, 2);
    }
    */
 }

I've commented out the part that gives the error. What are my options to confirm the end of each line is CRLF?

Answer 1

As others have said in the comments, you can't use ReadLine() and expect to find the EOL characters in the returned string. Now, if I understand you correctly, with StreamReader, you can do something like this:

using (var sr = new StreamReader(filePath))
{
    long position = 0;
    char[] buffer;
    while (sr.Peek() >= 0)
    {
        buffer = new char[513];
        sr.Read(buffer, 0, buffer.Length);
        if (buffer[511] == '\r' && buffer[512] == '\n')
        {
            position += 513;
            Console.WriteLine("CRLF");
        }
        else if (buffer[511] == '\r' || buffer[511] == '\n')
        {
            position += 512;
            sr.BaseStream.Seek(position, SeekOrigin.Begin);
            sr.DiscardBufferedData();
            Console.WriteLine("CR or LF");
        }
        else
        {
            Console.WriteLine("Something went wrong!");
            break;
        }
    }
}

This will read chunks of 513 characters at a time and check for the following:

• If the last two characters are CRLF, then we're good to go and it will continue reading the next 513 characters.

• If the above test doesn't pass but the character in position 511 is either a CR or an LF, it will set the position one character back (considering that the previous "line" was 512 characters, not 513) and continue reading the next 513 characters.

• If none of the above tests passes (i.e., the character in position 511 is neither CR nor LF), it will exit the loop. You can adjust this as per your requirements.

And if you wanted to access the current line as a string, you can easily do that using something like:

string line = new string(buffer, 0, 511);