CsvCSharp 0.1.5

Csv-CSharp

Csv-CSharp is a highly performant CSV (TSV) parser for .NET and Unity. It is designed to parse UTF-8 binaries directly and leverage Source Generators to enable serialization/deserialization between CSV (TSV) and object arrays with zero (or very low) allocation.

Installation

NuGet packages

Csv-CSharp requires .NET Standard 2.1 or higher. The package can be obtained from NuGet.

PM> Install-Package CsvCSharp

Unity

You can install Csv-CSharp in Unity by using NugetForUnity. For details, refer to the NugetForUnity README.

Quick Start

Csv-CSharp serializes/deserializes CSV data to and from arrays of classes/structs.

Define a class/struct and add the [CsvObject] attribute and the partial keyword.

[CsvObject]
public partial class Person
{
    [Column(0)]
    public string Name { get; set; }

    [Column(1)]
    public int Age { get; set; }
}

All public fields/properties of a type marked with [CsvObject] must have either the [Column] or [IgnoreMember] attribute. (An analyzer will output a compile error if it does not find either attribute on public members.)

The [Column] attribute can specify a column index as an int or a header name as a string.

To serialize this type to CSV or deserialize it from CSV, use CsvSerializer.

var array = new Person[]
{
    new() { Name = "Alice", Age = 18 },
    new() { Name = "Bob", Age = 23 },
    new() { Name = "Carol", Age = 31 },
}

// Person[] -> CSV (UTF-8)
byte[] csv = CsvSerializer.Serialize(array);

// Person[] -> CSV (UTF-16)
string csvText = CsvSerializer.SerializeToString(array);

// CSV (UTF-8) -> Person[]
array = CsvSerializer.Deserialize<Person>(csv);

// CSV (UTF-16) -> Person[]
array = CsvSerializer.Deserialize<Person>(csvText);

Serialize has an overload that returns a UTF-8 encoded byte[], and you can also pass a Stream or IBufferWriter<byte> for writing. Deserialize accepts UTF-8 byte arrays as byte[] and also supports string, Stream, and ReadOnlySequence<byte>.

The default supported types for fields are sbyte, byte, short, ushort, int, uint, long, ulong, char, string, Enum, Nullable<T>, DateTime, TimeSpan, and Guid. To support other types, refer to the Extensions section.

Serialization

The class/struct passed to CsvSerializer should have the [CsvObject] attribute and the partial keyword.

By default, fields and properties with the [Column] attribute are the targets for serialization/deserialization. The [Column] attribute is mandatory for public members, but you can target private members by adding the [Column] attribute.

[CsvObject]
public partial class Person
{
    [Column(0)]
    public string Name { get; set; }

    [Column(1)]
    int age;

    [IgnoreMember]
    public int Age => age;
}

To specify header names instead of indices, use a string key.

[CsvObject]
public partial class Person
{
    [Column("name")]
    public string Name { get; set; }

    [Column("age")]
    public int Age { get; set; }
}

To use member names as keys, specify [CsvObject(keyAsPropertyName: true)]. In this case, the [Column] attribute is not required.

[CsvObject(keyAsPropertyName: true)]
public partial class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
}

[!NOTE] Currently, deserialization with a specified constructor is not implemented. Types marked with [CsvObject] require a parameterless constructor. This feature is expected to be implemented by version 1.0.

CsvDocument

If you need to directly parse CSV fields, you can use CsvDocument.

var array = new Person[]
{
    new() { Name = "Alice", Age = 18 },
    new() { Name = "Bob", Age = 23 },
    new() { Name = "Carol", Age = 31 },
};

byte[] csv = CsvSerializer.Serialize(array);

// CSV (UTF-8) -> CsvDocument
var document = CsvSerializer.ConvertToDocument(csv);

foreach (var row in document.Rows)
{
    var name = row["Name"].GetValue<string>();
    var age = row["Age"].GetValue<int>();
}

Options

You can change CSV settings by passing CsvOptions to Serialize/Deserialize.

CsvSerializer.Serialize(array, new CsvOptions()
{
    HasHeader = true, // Include header row
    AllowComments = true, // Allow comments starting with '#''
    NewLine = NewLineType.LF, // Newline type
    Separator = SeparatorType.Comma, // Separator character
    QuoteMode = QuoteMode.Minimal, // Conditions for quoting fields (Minimal quotes only strings containing escape characters)
    FormatterProvider = StandardFormatterProvider.Instance, // ICsvFormatterProvider to use
});

CSV Specifications

The default settings of Csv-CSharp generally follow the specifications outlined in RFC 4180. However, please note that for performance and practicality reasons, some specifications may be disregarded.

• The default newline character is LF instead of CRLF.
• Records with a mismatch in the number of fields can be read without errors being output; missing fields will be set to their default values.

Extensions

Interfaces ICsvFormatter<T> and ICsvFormatterProvider are provided to customize field serialization/deserialization.

Use ICsvFormatter<T> for type serialization/deserialization. Here is an example of implementing a formatter for a struct wrapping an int.

public struct Foo
{
    public int Value;

    public Foo(int value)
    {
        this.Value = value;
    }
}

public sealed class FooFormatter : ICsvFormatter<Foo>
{
    public Foo Deserialize(ref CsvReader reader)
    {
        var value = reader.ReadInt32();
        return new Foo(value);
    }

    public void Serialize(ref CsvWriter writer, Foo value)
    {
        writer.WriteInt32(value.Value);
    }
}

Next, implement a formatter provider to retrieve the formatter.

public class CustomFormatterProvider : ICsvFormatterProvider
{
    public static readonly ICsvFormatterProvider Instance = new CustomFormatterProvider();

    CustomFormatterProvider()
    {
    }

    static CustomFormatterProvider()
    {
        FormatterCache<Foo>.Formatter = new FooFormatter();
    }

    public ICsvFormatter<T>? GetFormatter<T>()
    {
        return FormatterCache<T>.Formatter;
    }

    static class FormatterCache<T>
    {
        public static readonly ICsvFormatter<T> Formatter;
    }
}

You can set the created formatter provider in CsvOptions. The above CustomFormatterProvider only supports the Foo struct, so combine it with the standard formatter provider StandardFormatterProvider.

var array = new Foo[10];

// Create a composite formatter provider combining multiple formatter providers
var provider = CompositeFormatterProvider.Create(
    CustomFormatterProvider.Instance,
    StandardFormatterProvider.Instance
);

CsvSerializer.Serialize(array, new CsvOptions()
{
    FormatterProvider = provider
});

License

This library is released under the MIT license.