NCsv

.NET Standard 2.0 class library for object to CSV serialization and CSV to object deserialization.

NuGet Package

Usage

Serialization and Deserialization (Use Attribute)

Set the CsvColumnAttribute to the property of the class to be serialized.

class User
{
    [CsvColumn(0, Name = "CustomName")]
    public string Name { get; set; } = string.Empty;

    [CsvColumn(1)]
    [CsvFormat("yyyy/MM/dd")]
    public DateTime Birthday { get; set; }

    [CsvColumn(2)]
    public int Height { get; set; }
}

This is the code to serialize.

var users = new User[]
{
    new User()
    {
        Name = "Jackson",
        Birthday = new DateTime(2000, 1, 1),
        Height = 180,
    },
    new User()
    {
        Name = "Foo,Bar",
        Birthday = new DateTime(2001, 1, 1),
        Height = 170,
    },
};

var cs = new CsvSerializer<User>()
{
    HasHeader = true,
};

// Serialize.
string csv = cs.Serialize(users);

// CustomName,Birthday,Height
// Jackson,2000/01/01,180
// "Foo,Bar",2001/01/01,170
Debug.WriteLine(csv);

try
{
    // Deserialize.
    List<User> deserializedUsers = cs.Deserialize(csv);
}
catch (CsvValidationException ex)
{
    // Handle validation errors.
    Debug.WriteLine(ex.Message);
}

// You can also retrieve all validation errors beforehand
// with the CsvSerializer.GetErrors method.
List<CsvErrorItem> errors = cs.GetErrors(csv);
errors.ForEach(error => Debug.WriteLine(error));

// Serialize to file.
using (var writer = new StreamWriter(@"C:\users.csv"))
{
    cs.Serialize(writer, users);
}

// Deserialize from a file.
using (var reader = new StreamReader(@"C:\users.csv"))
{
    List<User> fileUsers = cs.Deserialize(reader);
}

Serialization and Deserialization (Use CsvSerializerBuilder)

It is also possible to serialize using CsvSerializerBuilder without using Attribute.
What you can do with Attribute is also designed to do with CsvSerializerBuilder.

class User
{
    public string Name { get; set; } = string.Empty;
    public DateTime Birthday { get; set; }
    public int Height { get; set; }
}

How to use CsvSerializerBuilder

var users = new User[]
{
    new User()
    {
        Name = "Jackson",
        Birthday = new DateTime(2000, 1, 1),
        Height = 180,
    },
    new User()
    {
        Name = "Foo,Bar",
        Birthday = new DateTime(2001, 1, 1),
        Height = 170,
    },
};

var cb = new CsvSerializerBuilder<User>();
cb.AddColumn(0, x => x.Name).Name("CustomName")
cb.AddColumn(1, x => x.Birthday).Format("yyyy/MM/dd");
cb.AddColumn(2, x => x.Height);

// Convert to CsvSerializer.
var cs = cb.ToCsvSerializer();

// Serialize.
string csv = cs.Serialize(users);

try
{
    // Deserialize.
    List<User> deserializedUsers = cs.Deserialize(csv);
}
catch (CsvValidationException ex)
{
    // Handle validation errors.
    Debug.WriteLine(ex.Message);
}

// The rest is the same as using Attribute.

After you have instantiated CsvSerializer, see here.

Validation

You can use the Attribute to validate the value.
If there is a validation error, CsvValidationException will be thrown when CsvSerializer.Deserialize is called.

class User
{
    [CsvColumn(0)]
    [CsvMaxLength(100)]
    [CsvRequired]
    public string Name { get; set; } = string.Empty;

    [CsvColumn(1)]
    [CsvNumber(3, 0, MinValue = "0")]
    public int Height { get; set; }
}

Customize message

Implement ICsvValidationMessage or inherit CsvValidationDefaultMessage.
See CsvValidationDefaultMessage.cs for an example.

class CustomMessage : ICsvValidationMessage
{
    public string GetNumericConvertError(ICsvItemContext context)
    {
        return $"The {context.Name} on line {context.LineNumber} must be set to a numeric value.";
    }
}

Use it.

CsvConfig.Current.ValidationMessage = new CustomMessage();

Custom validation attributes

Inherit the CsvValidationAttribute to create your own validation attribute.

[AttributeUsage(AttributeTargets.Property)]
public class ExampleValidationAttribute : CsvValidationAttribute
{
    public override bool Validate(CsvValidationContext context, out string errorMessage)
    {
        errorMessage = string.Empty;

        if (string.IsNullOrEmpty(context.Value))
        {
            errorMessage = $"{context.Name} is error.";
            return false;
        }

        return true;
    }
}

Use it.

[CsvColumn(0)]
[ExampleValidation]
public string PropertyA { get; set; }

You can also inherit the CsvRegularExpressionAttribute.

[AttributeUsage(AttributeTargets.Property)]
public class CsvNumberOnlyAttribute : CsvRegularExpressionAttribute
{
    public CsvNumberOnlyAttribute()
    {
        this.Pattern = "^[0-9]+$";
    }

    protected override string GetErrorMessage(ICsvItemContext context)
    {
        return $"{context.Name} must be set to a number only.";
    }
}

Customize the conversion

You can customize the conversion process, so you can support your own types.

Create a class to type a property.

class ValueObject
{
    private readonly string value;

    public ValueObject(string value)
    {
        this.value = value;
    }

    public override string ToString()
    {
        return this.value;
    }
}

Create a converter by inheriting CsvConverter.

class ValueObjectConverter : CsvConverter
{
    public bool TryConvertToObjectItem(ConvertToObjectItemContext context, out object result, out string errorMessage)
    {
        result = new ValueObject(context.CsvItem);
        errorMessage = string.Empty;
        return true;
    }
}

It is a class to serialize.

class Foo
{
    [CsvColumn(0)]
    [CsvConverter(typeof(ValueObjectConverter))]
    public ValueObject PropertyA { get; set; }
}