Reading CSV files using C#

Question

I\'m writing a simple import application and need to read a CSV file, show result in a DataGrid and show corrupted lines of the CSV file in another grid. For ex

Answer 1

Here's a solution I coded up today for a situation where I needed to parse a CSV without relying on external libraries. I haven't tested performance for large files since it wasn't relevant to my particular use case but I'd expect it to perform reasonably well for most situations.

        static List> ParseCsv(string csv) {
            var parsedCsv = new List>();
            var row = new List();
            string field = "";
            bool inQuotedField = false;

            for (int i = 0; i < csv.Length; i++) {
                char current = csv[i];
                char next = i == csv.Length - 1 ? ' ' : csv[i + 1];

                // if current character is not a quote or comma or carriage return or newline (or not a quote and currently in an a quoted field), just add the character to the current field text
                if ((current != '"' && current != ',' && current != '\r' && current != '\n') || (current != '"' && inQuotedField)) {
                    field += current;
                } else if (current == ' ' || current == '\t') {
                    continue; // ignore whitespace outside a quoted field
                } else if (current == '"') {
                    if (inQuotedField && next == '"') { // quote is escaping a quote within a quoted field
                        i++; // skip escaping quote
                        field += current;
                    } else if (inQuotedField) { // quote signifies the end of a quoted field
                        row.Add(field);
                        if (next == ',') {
                            i++; // skip the comma separator since we've already found the end of the field
                        }
                        field = "";
                        inQuotedField = false;
                    } else { // quote signifies the beginning of a quoted field
                        inQuotedField = true; 
                    }
                } else if (current == ',') { //
                    row.Add(field);
                    field = "";
                } else if (current == '\n') {
                    row.Add(field);
                    parsedCsv.Add(new List(row));
                    field = "";
                    row.Clear();
                }
            }

            return parsedCsv;
        }