OptionTypes 1.1.0

OptionTypes

Description

OptionTypes is a package to use some useful monads in C#. It contains basically 2 classes:

• The Maybe<T> class allows to create an item of type T that may have no value. This value cannot be accessed in an unsafe manner, making really easy to completely remove null references from your code and reducing the number of NullReferenceException thrown.

• The Result class represents an operation that has been completed. It's slim API makes taking a decision based on the result of the operation straightforward.

How to use it

To create a variable as a Maybe<T>, helper methods in the static Maybe class can be used, or use the static Some/None methods in Maybe<T> class.

To use the value inside the Maybe class, use the Map, Bind, Match or ValueOr methods.

To create a Result type, use the static methods Ok/Error.

Usage example

Maybe

public static async Task Main(string[] args)
{
    var userTelephone = await GetUser(args[0])
        .Map(u => u.Telephone);

    Console.WriteLine(userTelephone.ValueOr("Telephone not found"));
}

private static async Task<Maybe<User>> GetUser(string id)
{
    var user = await UserManager.GetAsync(id);

    return Maybe.FromValue(user);
}

Result

public Result<Unit, string> WriteFile(string path, byte[] content)
{
    try
    {
        File.WriteAllBytes(path, content);

        return Result<Unit, string>.Ok(default);
    }
    catch
    {
        return Result<Unit, string>.Error("Error");
    }
}

public static void Main(string[] args)
{
    var result = WriteFile(path, content);

    result.Match(
        _ => Console.WriteLine("Success"),
        err => Console.WriteLine(err)
    );
}

Usage inside Entity Framework Core

This uses the internal EF Api

The project OptionTypes.Ef contains the ValueConverters needed to map the Maybe<T> type to the Entity Framework columns.

In the OnModelCreating method overriden in your DbContext, call AddOptionTypeConverters. This will add all the converters needed in your model.