Functional Programing in c#

Response<TValue> is a simple class (monad) that contains value or errors.

Here is a simple usage of return error. Usage for validation methods.

    public static Response<int> DivideByZero(int value, int divider)
    {
        if (divider == 0)
        {
            return "Divider value cannot be zero.";
        }

        return value / divider;
    }

Combine methods by using Then method.

    public static Response ProcessByUserId(int userId)
    {
        return GetUserFromDatabase(userId)
              .Then(SendEMailForUser)
              .Then(MarkUserAsMailNotificationCompleted)
              .Then(SaveUser);
    }

    public static Response<UserInfo> GetUserFromDatabase(int userId)
    {
        throw new NotImplementedException();
    }

    public static Response<UserInfo> SendEMailForUser(UserInfo userInfo)
    {
        throw new NotImplementedException();
    }

    public static Response<UserInfo> MarkUserAsMailNotificationCompleted(UserInfo userInfo)
    {
        throw new NotImplementedException();
    }

    public static Response<UserInfo> SaveUser(UserInfo userInfo)
    {
        throw new NotImplementedException();
    }
    public class UserInfo
    {
    }

Usage of Pipe

    public static Response ProcessByUserId(int userId)
    {
        return Pipe(userId,
                    GetUserFromDatabase,
                    SendEMailForUser,
                    MarkUserAsMailNotificationCompleted,
                    SaveUser);
    }

Here is my best practices in functional programing

Avoid mutable states
Avoid side effect
Methods should be pure
Write code in declerative style
Seperate processed data and methods
Write for humans not machines
Use inline methods for reduce parameter passing problems
if method is too complex then seperate flow into a pipe method so you can read main code block more clearly. No need to compile codes in your brain.
Do not pass any monad as parameter to another method.

beyaz/FunctionalProgramingInCSharp

Functional Programing in c#

Here is my best practices in functional programing