CsvHelper

using CsvHelper;

using var reader = CsvReader.FromFile("orders.csv");    // or Create(stream), Create(byte[]), Create(TextReader), FromText(string)
var price = reader.GetFieldIndex("Unit Price");         // header lookup: exact, then ignoring case and whitespace
while (reader.Read())
{
    string id = reader.GetString(0);                    // by index
    string name = reader.GetString("Name");             // by header name
    decimal unitPrice = reader.Parse<decimal>(price);   // also int, long, double, bool, DateTime, Guid, ...
    ReadOnlySpan<byte> raw = reader.GetSpan(3);         // UTF-8, already unquoted, no allocation
    DateOnly ordered = reader.Parse<DateOnly>(4);       // any ISpanParsable<T> (.NET 8 and later)
}

using CsvHelper;

[CsvRecord]
public partial class Order
{
    public string Id { get; set; } = "";
    [CsvColumn("Unit Price")]
    public decimal Price { get; set; }
    [CsvColumn(Optional = true)]
    public int? Quantity { get; set; }
    [CsvIgnore]
    public decimal Total { get; set; }
}

[CsvRecord]
public partial record Line(string Sku, [CsvColumn(Index = 3)] double Weight, int Count = 1);

using var reader = CsvReader.FromFile("orders.csv");
foreach (Order order in reader.GetRecords<Order>()) { }          // also GetRecordsAsync<T>() and ParallelEnumerate<T>()
while (reader.Read()) { Order order = reader.GetRecord<Order>(); } // the current record

using var writer = CsvWriter.ToFile("copy.csv");
writer.WriteRecords(orders);                                     // the header, then the records

using CsvHelper;

using var writer = CsvWriter.ToFile("out.csv");           // or Create(stream), Create(TextWriter)
writer.WriteHeader("Id", "Name", "Price", "When");
foreach (var item in items)
{
    writer.WriteField(item.Id);                           // numbers format straight to UTF-8
    writer.WriteField(item.Name);                         // quoted only if it contains , " CR or LF
    writer.WriteField(item.Price);
    writer.WriteField(item.Timestamp);                    // DateTime/DateTimeOffset: ISO 8601 ("O") by default
    writer.EndRecord();                                   // or await writer.EndRecordAsync()
}