CODEWITHSUNDEEP
c#csv
Paul Lambert
Paul Lambert

Reputation: 420

Parsing CSV strings (not files) in C#

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.

Upvotes: 0

Views: 225

Answers (1)

glut
glut

Reputation: 51

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;
}

Upvotes: 3

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