Dameng.SepEx

A high-performance, Native AOT compatible source generator for working with separated values (CSV/TSV) files in C#. This library extends the excellent Sep library by providing compile-time code generation for strongly-typed reading and writing of CSV data.

Perfect for developers migrating from CSVHelper who need Native AOT support or want better performance through source generation.

Features

• Source Generator: Automatically generates type-safe CSV readers and writers at compile time
• High Performance: Built on top of the fast Sep library
• Attribute-Based Configuration: Use attributes to configure column mapping, formatting, and behavior
• Flexible Column Mapping: Support for column names, indexes, default values, and formatting
• Type Safety: Compile-time type checking and IntelliSense support
• NativeAOT Compatible: Full support for Native AOT compilation, unlike CSVHelper

Installation

Install the NuGet packages:

dotnet add package Dameng.SepEx

Usage & Migration

Basic Usage

Define your data model as a partial class with [GenSepParsable] and use attributes to configure column mapping:

[GenSepParsable]
public partial class Person
{
    [SepColumnName("FullName")]
    [SepColumnIndex(0)]
    public string Name { get; set; }
    
    [SepColumnName("Age")]
    public int Age { get; set; }
    
    [SepDefaultValue("Unknown")]
    public string City { get; set; }
    
    [SepColumnIgnore]
    public string InternalId { get; set; }
}

// Reading CSV
using var reader = Sep.Reader().FromFile("people.csv");
foreach (var person in reader.GetRecords<Person>())
{
    Console.WriteLine($"{person.Name} is {person.Age} years old");
}

// Writing CSV
var people = new List<Person> { /* ... */ };
using var writer = Sep.Writer().ToFile("output.csv");
writer.WriteRecords(people);

Migrating from CSVHelper

If you're migrating from CSVHelper, simply update your attributes and make classes partial:

CSVHelper	Dameng.SepEx
[Name("column")]	[SepColumnName("column")]
[Index(0)]	[SepColumnIndex(0)]
[Ignore]	[SepColumnIgnore]
[Default("value")]	[SepDefaultValue("value")]
[Format("format")]	[SepColumnFormat("format")]

Key changes:

• Add [GenSepParsable] attribute and make class partial
• Replace CSVHelper attributes with Dameng.SepEx equivalents
• Use Sep.Reader() and Sep.Writer() instead of CSVHelper APIs

External Data Models

For classes you can't modify (e.g., from external libraries), use type info generation:

[GenSepTypeInfo<ExternalPerson>()]
public partial class ExternalPersonTypeInfo;

// Usage
using var reader = Sep.Reader().FromFile("people.csv");
foreach (var person in reader.GetRecords<ExternalPerson>(ExternalPersonTypeInfo.ExternalPerson))
{
    // Process person
}

Available Attributes

• [GenSepTypeInfo<T>()]: Generate type info for the specified type
• [SepColumnName(string name)]: Specify column name
• [SepColumnIndex(int index)]: Specify column index for reading/writing order
• [SepDefaultValue(object value)]: Set default value when column is missing
• [SepColumnIgnore]: Ignore property/field during CSV operations
• [SepColumnFormat(string format)]: Specify format for writing values

License

This project is licensed under the MIT License - see the LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.