A Simple CSV Reader

Introduction 

This tip details a simple method to read CSV files.

Using the code

The main problem  when reading CSV is to determine when a comma is being used to separate values from each other and when  a comma is not a separator but part of a value. The following snippet resolves this problem:

if (c == ‘,’ && quoteCount % 2 == 0)
{
//comma is being used as a separator
}

Where variable c is the character under consideration and quoteCount is the running total of ‘”’ characters  in the string at this point. Using this method it is possible to write a simple, if not robust, CSV Reader in a few lines of code.

public static List<List<string>> ReadCsv(string[] data, char separator)
{
    var rows = new List<List<string>>();
    foreach (string text in data)
    {
        int quoteCount = 0;
        int startIndex = 0;
        int endIndex = 0;
        var cols = new List<string>();
        foreach (char c in text)
        {
            if (c == '"')
            {
              quoteCount += 1;
            }
            else
            {
             if (c == separator && quoteCount % 2 == 0)
              {
               cols.Add(trimQuotes(text.Substring(startIndex, endIndex - startIndex)));
               startIndex = endIndex + 1;
              }
            }
            endIndex++;
        }
        cols.Add(trimQuotes(text.Substring(startIndex, endIndex - startIndex)));
        rows.Add(cols);
    }
    return rows;
}

private static string trimQuotes(string text)
{
    if (String.IsNullOrEmpty(text))
    {
        return text;
    }
    return text[0] == '"' && text.Length > 2
               ? text.Substring(1, text.Length - 2).Replace("\"\"", "\"")
               : text.Replace("\"\"", "\"");
}

Conclusion

I am grateful to Jonathan Wood's excellent article, Reading and Writing CSV Files in C# , for the inspiration to write this tip. His method for parsing text into the CSV format is simply brilliant.