Parsing CSV strings (not files) in C#

Question

Using C#, I need to parse a CSV string that doesn't come from a file. I've found a great deal of material on parsing CSV files, but virtually nothing on strings. It seems as though this should be simple, yet thus far I can come up only with inefficient methods, such as this:

using Microsoft.VisualBasic.FileIO;

var csvParser = new TextFieldParser(new StringReader(strCsvLine));
csvParser.SetDelimiters(new string[] { "," });
csvParser.HasFieldsEnclosedInQuotes = true;

Are there good ways of making this more efficient and less ugly? I will be processing huge volumes of strings, so I wouldn't want to pay the cost of all the above. Thanks.

Why do you call the solution you have at hand as inefficient? What efficiency are you expecting from a different solution? — Vikas Gupta
– Vikas Gupta, Commented Oct 10, 2014 at 2:00
Thanks -- yes, I saw that SO entry, but it's generally about files, not strings. As for efficiency, I don't think I want to create a new TextFieldParser and a new StringReader for every single string, since this seems hugely wasteful. Still, I'm starting to believe it may not be so bad after all, given the Pandora's Box I've managed to open. — Paul Lambert
– Paul Lambert, Commented Oct 10, 2014 at 2:04
You have a valid CSV string? Split on Environment.Newline, then on commas. What's the problem? — Jonesopolis
– Jonesopolis, Commented Oct 10, 2014 at 2:38
@Jonesy: I'm gonna guess, from the example the OP has given, that they have commas that are enclosed within quotes that shouldn't be split. Still, it's only slightly more complicated. — Matt Burland
– Matt Burland, Commented Oct 10, 2014 at 2:48

glut · Accepted Answer · 2023-04-15 19:49:21Z

3

Here is a lightly tested parser that handles quotes

public List<string> Parse(string line)
{
    var columns = new List<string>();
    var sb = new StringBuilder();
    bool isQuoted = false;

    for (int i = 0; i < line.Length; i++)
    {
        char c = line[i];

        // If the current character is a double quote
        if (c == '"')
        {
            // If we're not inside a quoted section, set isQuoted to true
            if (!isQuoted && sb.Length == 0)
            {
                isQuoted = true;
            }
            else if (isQuoted && i + 1 < line.Length && line[i + 1] == '"') // Check for escaped double quotes
            {
                sb.Append('"');
                i++; // Skip the next quote
            }
            else if (isQuoted) // If the next character is not a double quote, set isQuoted to false
            {
                isQuoted = false;
            }
            else // Not a quoted string
            {
                sb.Append('"');
            }
            continue;
        }

        // If the current character is a comma and we're not inside a quoted section, add the column and clear the StringBuilder
        if (!isQuoted && c == ',')
        {
            columns.Add(sb.ToString());
            sb.Clear();
            continue;
        }

        // Append the character to the current column
        sb.Append(c);
    }

    // Add the last column
    columns.Add(sb.ToString());

    return columns;
}

edited Apr 15, 2023 at 19:49

answered Jun 1, 2022 at 2:31

glut

796 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Enigmativity Over a year ago

I tested against var examples = new [] { "x,y", "x,\"y\"", "x,\"y\",z", "x,\"y,w\",z", "x,\"y,\"\"w\",z", }; and it works pretty well. Well done!

Collectives™ on Stack Overflow

Parsing CSV strings (not files) in C#

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related