csv

Really simple csv library

This library targets .NET Standard 2.0, .NET 8.0, and .NET 9.0, with enhanced Span/Memory APIs available for .NET 8.0+.

Install

To install csv, use the following command in the Package Manager Console

PM> Install-Package Csv

Basic Usage

More examples can be found in the tests.

Reading a CSV file

// NOTE: Library assumes that the csv data will have a header row by default, see CsvOptions.HeaderMode
/*
# comments are ignored
Column name,Second column,Third column
First cell,second cell,
Second row,second cell,third cell
*/ 
var csv = File.ReadAllText("sample.csv");
foreach (var line in CsvReader.ReadFromText(csv))
{
    // Header is handled, each line will contain the actual row data
    var firstCell = line[0];
    var byName = line["Column name"];
}

CsvReader also supports reading from a TextReader (CsvReader.Read(TextReader, CsvOptions)) or a Stream (CsvReader.ReadFromStream(Stream, CsvOptions))

For .NET 8.0+ the library exposes:

• CsvReader.ReadAsync and CsvReader.ReadFromStreamAsync which return IAsyncEnumerable<ICsvLine>
• CsvReader.ReadFromMemory to read from a ReadOnlyMemory<char> without allocating intermediate strings
• CsvReader.ReadAsSpan, CsvReader.ReadFromStreamAsSpan, and CsvReader.ReadFromTextAsSpan which return IEnumerable<ICsvLineSpan> for zero-allocation Span/Memory access to CSV data
• CsvReader.ReadFromMemoryOptimized with CsvMemoryOptions for high-performance scenarios using ArrayPool-based buffering

High-performance reading with Span/Memory (.NET 8.0+)

var csv = File.ReadAllText("sample.csv");
foreach (var line in CsvReader.ReadFromTextAsSpan(csv))
{
    // Access data as ReadOnlySpan<char> for zero allocations
    ReadOnlySpan<char> firstCell = line.GetSpan(0);
    ReadOnlySpan<char> byName = line.GetSpan("Column name");

    // Or as ReadOnlyMemory<char> if you need to store references
    ReadOnlyMemory<char> cellMemory = line.GetMemory(0);
}

CsvOptions can be used to configure the csv parsing:

var options = new CsvOptions // Defaults
{
    RowsToSkip = 0, // Allows skipping of initial rows without csv data
    SkipRow = (row, idx) => string.IsNullOrEmpty(row) || row[0] == '#',
    Separator = '\0', // Autodetects based on first row
    TrimData = false, // Can be used to trim each cell
    Comparer = null, // Can be used for case-insensitive comparison for names
    HeaderMode = HeaderMode.HeaderPresent, // Assumes first row is a header row
    ValidateColumnCount = false, // Checks each row immediately for column count
    ReturnEmptyForMissingColumn = false, // Allows for accessing invalid column names
    Aliases = null, // A collection of alternative column names
    AllowNewLineInEnclosedFieldValues = false, // Respects new line (either \r\n or \n) characters inside field values enclosed in double quotes.
    AllowBackSlashToEscapeQuote = false, // Allows the sequence "\"" to be a valid quoted value (in addition to the standard """")
    AllowSingleQuoteToEncloseFieldValues = false, // Allows the single-quote character to be used to enclose field values
    NewLine = Environment.NewLine // The new line string to use when multiline field values are read (Requires "AllowNewLineInEnclosedFieldValues" to be set to "true" for this to have any effect.)
};

Writing a CSV file

With headers

var columnNames = new [] { "Id", "Name" };
var rows = new []
{
    new [] { "0", "John Doe" },
    new [] { "1", "Jane Doe" }
};
var csv = CsvWriter.WriteToText(columnNames, rows, ',');
File.WriteAllText("people.csv", csv);
/*
Writes the following to the file:

Id,Name
0,John Doe
1,Jane Doe
*/

Without headers

var rows = new []
{
    new [] { "0", "John Doe" },
    new [] { "1", "Jane Doe" }
};
// Convenience overload - no need to pass headers or skipHeaderRow
var csv = CsvWriter.WriteToText(rows);
File.WriteAllText("people.csv", csv);
/*
Writes the following to the file (no header row):

0,John Doe
1,Jane Doe
*/

Skipping headers

var columnNames = new [] { "Id", "Name" };
var rows = new []
{
    new [] { "0", "John Doe" },
    new [] { "1", "Jane Doe" }
};
// Pass null for headers and skipHeaderRow: true
// Column count is determined from the first data row
var csv = CsvWriter.WriteToText(null, rows, ',', skipHeaderRow: true);

Custom separator

var rows = new [] { new [] { "A", "B" }, new [] { "C", "D" } };
var csv = CsvWriter.WriteToText(rows, ';'); // semicolon separator
// Output: A;B
//         C;D

CsvWriter also includes asynchronous overloads (WriteAsync and WriteToTextAsync) which operate on IAsyncEnumerable<string[]> and support passing a CancellationToken. For .NET 8.0+, memory-efficient overloads using ReadOnlyMemory<char> are available.

Helper extensions

CsvReader provides extension methods to work with the returned IEnumerable<ICsvLine>:

• GetColumn(int columnNo) / GetColumn<T>(int columnNo, Func<string, T>) – extract a single column from all rows.
• GetBlock(int row_start = 0, int row_length = -1, int col_start = 0, int col_length = -1) – get a rectangular subset of the data.

Status

License