Shallow Copy and Deep Copy

      A shallow copy creates a new instance of the same type as the original object, and then copies the non-static fields of the original object.

The MemberwiseClone method creates a shallow copy by creating a new object, and then copying the non static fields of the current object to the new object. If the field is a value type, a bit-by-bit copy of the field is performed. If the field is a reference type, the reference is copied but the referred object is not; 

Simply saying, shallow copy copies the structure of the object, deep copy copies structure as well as data

In a deep copy, all objects are duplicated; whereas, in a shallow copy, only the top-level objects are duplicated and the lower levels contain references..

           For example, consider an object called X that references objects A and B. Object B, in turn, references object C. A shallow copy of X creates new object X2 that also references objects A and B. In contrast, a deep copy of X creates a new object X2 that references the new objects A2 and B2, which are copies of A and B. B2, in turn, references the new object C2, which is a copy C. Use a class that implements the ICloneable interface to perform a deep or shallow copy of an object.

The following program will explain ...

namespace shallowcopyingexpl {    public class IdInfo     {         public int IdNumber;         public IdInfo(int IdNumber)         {             this.IdNumber = IdNumber;         }     }     public class Person     {         public int Age;         public string Name;         public IdInfo IdInfo;         public Person ShallowCopy()         {             return (Person)this.MemberwiseClone();         }         public Person DeepCopy()         {             Person other = (Person)this.MemberwiseClone();             other.IdInfo = new IdInfo(this.IdInfo.IdNumber);             return other;         }     }     public class Example     {         public static void Main()         {             // Create an instance of Person and assign values to its fields.             Person p1 = new Person();             p1.Age = 42;             p1.Name = "Sam";             p1.IdInfo = new IdInfo(6565);             // Perform a shallow copy of p1 and assign it to p2.             Person p2 = (Person)p1.ShallowCopy();             // Display values of p1, p2             Console.WriteLine("Original values of p1 and p2:");             Console.WriteLine("   p1 instance values: ");             DisplayValues(p1);             Console.WriteLine("   p2 instance values:");             DisplayValues(p2);             // Change the value of p1 properties and display the values of p1 and p2.             p1.Age = 32;             p1.Name = "Frank";             p1.IdInfo.IdNumber = 7878;             Console.WriteLine("\nValues of p1 and p2 after changes to p1:");             Console.WriteLine("   p1 instance values: ");             DisplayValues(p1);             Console.WriteLine("   p2 instance values:");             DisplayValues(p2);             // Make a deep copy of p1 and assign it to p3.             Person p3 = p1.DeepCopy();             // Change the members of the p1 class to new values to show the deep copy.             p1.Name = "George";             p1.Age = 39;             p1.IdInfo.IdNumber = 8641;             Console.WriteLine("\nValues of p1 and p3 after changes to p1:");             Console.WriteLine("   p1 instance values: ");             DisplayValues(p1);             Console.WriteLine("   p3 instance values:");             DisplayValues(p3);             Console.Read();         }         public static void DisplayValues(Person p)         {             Console.WriteLine("      Name: {0:s}, Age: {1:d}", p.Name, p.Age);             Console.WriteLine("      Value: {0:d}", p.IdInfo.IdNumber);         }     } } //changes in one object doesn't reflect the other object .just structure only copied from one object to other not data. Output: Original values of p1 and p2:    p1 instance values:       Name: Sam, Age: 42       Value: 6565    p2 instance values:       Name: Sam, Age: 42       Value: 6565 Values of p1 and p2 after changes to p1:    p1 instance values:       Name: Frank, Age: 32       Value: 7878    p2 instance values:       Name: Sam, Age: 42       Value: 7878 Values of p1 and p3 after changes to p1:    p1 instance values:       Name: George, Age: 39       Value: 8641    p3 instance values:       Name: Frank, Age: 32       Value: 7878