CSV parser, compliant with RFC4180 can be customized to do new line normalization and does handle new line in quoted string literal without reading all text up front

CSVParser.cs

static class CSV
{
	public struct Record
	{
		public readonly string[] Row;

		public string this[int index] => Row[index];

		public Record(string[] row)
		{
			Row = row;
		}
	}

	public static List<Record> ParseText(string text)
	{
		return Parse(new StringReader(text));
	}

	public static List<Record> ParseFile(string fn)
	{
		using (var reader = File.OpenText(fn))
		{
			return Parse(reader);
		}
	}

	public static List<Record> Parse(TextReader reader)
	{
		var data = new List<Record>();

		var col = new StringBuilder();
		var row = new List<string>();
		for (; ; )
		{
			var ln = reader.ReadLine();
			if (ln == null) break;
			if (Tokenize(ln, col, row))
			{
				data.Add(new Record(row.ToArray()));
				row.Clear();
			}
		}

		return data;
	}

	public static bool Tokenize(string s, StringBuilder col, List<string> row)
	{
		int i = 0;

		if (col.Length > 0)
		{
			col.AppendLine(); // continuation

			if (!TokenizeQuote(s, ref i, col, row))
			{
				return false;
			}
		}

		while (i < s.Length)
		{
			var ch = s[i];
			if (ch == ',')
			{
				row.Add(col.ToString().Trim());
				col.Length = 0;
				i++;
			}
			else if (ch == '"')
			{
				i++;
				if (!TokenizeQuote(s, ref i, col, row))
				{
					return false;
				}
			}
			else
			{
				col.Append(ch);
				i++;
			}
		}

		if (col.Length > 0)
		{
			row.Add(col.ToString().Trim());
			col.Length = 0;
		}

		return true;
	}

	public static bool TokenizeQuote(string s, ref int i, StringBuilder col, List<string> row)
	{
		while (i < s.Length)
		{
			var ch = s[i];
			if (ch == '"')
			{
				// escape sequence
				if (i + 1 < s.Length && s[i + 1] == '"')
				{
					col.Append('"');
					i++;
					i++;
					continue;
				}
				i++;
				return true;
			}
			else
			{
				col.Append(ch);
				i++;
			}
		}
		return false;
	}
}