What's the difference between struct and class in .NET?

Question

What\'s the difference between struct and class in .NET?

Answer 1

Besides the basic difference of access specifier, and few mentioned above I would like to add some of the major differences including few of the mentioned above with a code sample with output, which will give a more clear idea of the reference and value

Structs:

• Are value types and do not require heap allocation.
• Memory allocation is different and is stored in stack
• Useful for small data structures
• Affect performance, when we pass value to method, we pass the entire data structure and all is passed to the stack.
• Constructor simply returns the struct value itself (typically in a temporary location on the stack), and this value is then copied as necessary
• The variables each have their own copy of the data, and it is not possible for operations on one to affect the other.
• Do not support user-specified inheritance, and they implicitly inherit from type object

Class:

• Reference Type value
• Stored in Heap
• Store a reference to a dynamically allocated object
• Constructors are invoked with the new operator, but that does not allocate memory on the heap
• Multiple variables may have a reference to the same object
• It is possible for operations on one variable to affect the object referenced by the other variable

Code Sample

    static void Main(string[] args)
    {
        //Struct
        myStruct objStruct = new myStruct();
        objStruct.x = 10;
        Console.WriteLine("Initial value of Struct Object is: " + objStruct.x);
        Console.WriteLine();
        methodStruct(objStruct);
        Console.WriteLine();
        Console.WriteLine("After Method call value of Struct Object is: " + objStruct.x);
        Console.WriteLine();

        //Class
        myClass objClass = new myClass(10);
        Console.WriteLine("Initial value of Class Object is: " + objClass.x);
        Console.WriteLine();
        methodClass(objClass);
        Console.WriteLine();
        Console.WriteLine("After Method call value of Class Object is: " + objClass.x);
        Console.Read();
    }
    static void methodStruct(myStruct newStruct)
    {
        newStruct.x = 20;
        Console.WriteLine("Inside Struct Method");
        Console.WriteLine("Inside Method value of Struct Object is: " + newStruct.x);
    }
    static void methodClass(myClass newClass)
    {
        newClass.x = 20;
        Console.WriteLine("Inside Class Method");
        Console.WriteLine("Inside Method value of Class Object is: " + newClass.x);
    }
    public struct myStruct
    {
        public int x;
        public myStruct(int xCons)
        {
            this.x = xCons;
        }
    }
    public class myClass
    {
        public int x;
        public myClass(int xCons)
        {
            this.x = xCons;
        }
    }

Output

Initial value of Struct Object is: 10

Inside Struct Method Inside Method value of Struct Object is: 20

After Method call value of Struct Object is: 10

Initial value of Class Object is: 10

Inside Class Method Inside Method value of Class Object is: 20

After Method call value of Class Object is: 20

Here you can clearly see the difference between call by value and call by reference.