// REFERENCE TYPES

// https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/passing-reference-type-parameters

​

// A variable of a reference type does not contain its data directly; it contains a reference to its data.

// When you pass a reference-type parameter by value, it is possible to change the data belonging to the 

// referenced object, such as the value of a class member. However, you cannot change the value of the reference itself; 

// for example, you cannot use the same reference to allocate memory for a new object and have it persist outside the 

// method. To do that, pass the parameter using the ref or out keyword. For simplicity, the following examples use ref.

​

// VALUE TYPES

// https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/passing-value-type-parameters

​

// A value-type variable contains its data directly as opposed to a reference-type variable, which contains a reference 

// to its data. Passing a value-type variable to a method by value means passing a copy of the variable to the method. 

// Any changes to the parameter that take place inside the method have no affect on the original data stored in the

//  argument variable. If you want the called method to change the value of the argument, you must pass it by reference, 

// using the ref or out keyword. You may also use the in keyword to pass a value parameter by reference to avoid the copy 

// while guaranteeing that the value will not be changed. For simplicity, the following examples use ref.

​

​

using System;

​

​

namespace GradeBook.Tests

{

    public class Program

    {

        public void Main()

        {

            CSharpIsPassByValue();

        }

​

        public void CSharpIsPassByValue()

        {

            var book1 = GetBook("Book 1");

            GetBookSetName(book1, "New Name");

            // Assert.Equals("Book 1", book1.Name);

            Console.WriteLine(book1.Name.Equals(("Book 1"))); // <= 'True'

        }

​

        public Book GetBook(string name)

        {

            var book = new Book{Name = name}; // CAN change the value of a reference's data.

            return book;

        }

​

        public void GetBookSetName(Book book, string name)

        {

            book = new Book{Name = name}; // CANNOT change the value of a reference... only its data.

            book.Name = name;

        }

    }

​

    public class Book

    {

        public string Name

        {

            get;

            set;

        }

    }

}