Fluent Builder

ApplicationBuilder.cs

using System;
using System.Collections.Generic;

namespace FunWithPatterns.Builder
{
    public class ApplicationBuilder
    {
        private string _name;
        private string _sureName;
        private DateTime _birthDate;
        private string _scholarship;
        private IList<RepetentClass> _repetentClasses = new List<RepetentClass>();
        private decimal _repetentCost;
        private bool _dormitoryAssignment;
        private string _dormitoryName;
        private string _dormitoryAddress;

        public ApplicationBuilder CreateApplication(string name, string sureName, DateTime birthDate)
        {
            _name = name;
            _sureName = sureName;
            _birthDate = birthDate;

            return this;
        }

        public ApplicationBuilder WithScholarship(string scholarship)
        {
            _scholarship = scholarship;
            return this;
        }

        public ApplicationBuilder WithRepetition(string className, int theoryHours, int practicalHours, decimal repetentCost)
        {
            if (string.IsNullOrEmpty(className))
                throw new ArgumentNullException(nameof(className));
            
            _repetentClasses.Add(new RepetentClass
            {
                ClassName = className,
                TheoryHours = theoryHours,
                PracticalHours = practicalHours
            });
            _repetentCost += repetentCost;

            return this;
        }

        public ApplicationBuilder WithDormitoryAssignment(string dormitoryName, string dormitoryAddress)
        {
            _dormitoryAssignment = true;
            _dormitoryName = dormitoryName;
            _dormitoryAddress = dormitoryAddress;

            return this;
        }

        public RecruitmentApplication Build()
        {
            var application = new RecruitmentApplication();
            application.Name = _name;
            application.SureName = _sureName;
            application.BirthDate = _birthDate;

            application.Scholarship = _scholarship;

            application.RepetentClasses = _repetentClasses;
            application.RepetentCost = _repetentCost;

            application.DormitoryAssignment = _dormitoryAssignment;
            application.DormitoryName = _dormitoryName;
            application.DormitoryAddress = _dormitoryAddress;

            return application;
        }
    }
}

FirstApplicationBuilder.cs

using System;

namespace FunWithPatterns.Builder
{
    class FirstApplicationBuilder
    {
        private RecruitmentApplication _application;

        public FirstApplicationBuilder CreateApplication(string name, string sureName, DateTime birthDate)
        {
            _application = new RecruitmentApplication
            {
                Name = name,
                SureName = sureName,
                BirthDate = birthDate,
                RepetentClasses = new List<RepetentClass>()
            };

            return this;
        }

        public FirstApplicationBuilder WithScholarship(string scholarship)
        {
            _application.Scholarship = scholarship;
            return this;
        }

        public FirstApplicationBuilder WithRepetition(string className, int theoryHours, int practicalHours, decimal repetentCost)
        {
            if (string.IsNullOrEmpty(className))
                throw new ArgumentNullException(nameof(className));

            _application.RepetentClasses.Add(new RepetentClass
            {
                ClassName = className,
                TheoryHours = theoryHours,
                PracticalHours = practicalHours
            });

            _application.RepetentCost += repetentCost;

            return this;
        }

        public FirstApplicationBuilder WithDormitoryAssignment(string dormitoryName, string dormitoryAddress)
        {
            _application.DormitoryAssignment = true;
            _application.DormitoryName = dormitoryName;
            _application.DormitoryAddress = dormitoryAddress;

            return this;
        }

        public RecruitmentApplication Build()
        {
            return _application;
        }
    }
}

Program.cs

static void Main(string[] args)
{
    var builder = new ApplicationBuilder();
    var application = builder
        .CreateApplication("Zaba", "Zul", new DateTime(1990, 9, 2))
        .WithDormitoryAssignment("Filon", "Kilinskiego 11")
        .WithRepetition("Electronics", 10, 10, 550)
        .WithRepetition("Object Oriented Programming", 20, 15, 850)
        .Build();
}

RecruitmentApplication.cs

using System;
using System.Collections.Generic;

namespace FunWithPatterns.Builder
{
    public enum StudyType
    {
        FullTimeStudies,
        ExtramuralStudies
    }

    public class RecruitmentApplication
    {
        public string Name { get; set; }
        public string SureName { get; set; }
        public DateTime BirthDate { get; set; }
        public string FieldOfStudy { get; set; }
        public StudyType StudyType { get; set; }

        #region Freshman

        public string Scholarship { get; set; }
        
        #endregion

        #region Repetition

        public string IndexNumber { get; set; }
        public IList<RepetentClass> RepetentClasses { get; set; }
        public decimal RepetentCost { get; set; }

        #endregion

        #region Dormitory assignment

        public bool DormitoryAssignment { get; set; }
        public string DormitoryName { get; set; }
        public string DormitoryAddress { get; set; }

        #endregion
    }

    public class RepetentClass
    {
        public string ClassName { get; set; }
        public int TheoryHours { get; set; }
        public int PracticalHours { get; set; }
    }
}