Difference Between Struct And Class In C#

Structs are light versions of classes. Structs are value types and can be used to create objects that behave like the built-in types.

Structs share many features with classes but with the following limitations as compared to classes.

  • Struct cannot have default constructor (a constructor without parameters) or a destructor.

  • Structs are value type and copied on assignment.

  • Structs are value types while classes are reference types.

  • Structs can be instantiated without using a new operator.

  • A struct cannot inherit from another struct or class, and it cannot be the base of a class. All structs inherit directly from System.ValueType, which inherits from System.Object.

  • Struct cannot be base class. So, Struct types cannot abstract and are always implicitly sealed.

  •  Abstract and sealed modifiers are not allowed and struct member cannot be protected or protected internals.

  • Function members in a struct cannot be abstract or virtual, and the override modifier is allowed only to the override methods inherited fromSystem.ValueType.

  • Struct does not allow the instance field declarations to include variable initializers. But, static fields of a struct are allowed to include variable initializers.

  • A struct can implement interfaces.

  • A struct can be used as a nullable type and can be assigned a null value.

So, when to use struct or classes?

To answer this question, we should have good understanding of differences.

 S.N  Struct  Classes
 1  Structs are value types, allocated either on the stack or inline in containing types. Classes are reference types, allocated on the heap and garbage-collected. 
 2   Allocations and de-allocations of value types are in general cheaper than allocations and de-allocations of reference types.  Assignments of large reference types are cheaper than assignments of large value types.
 3 In structs, each variable contains its own copy of the data (except in the case of ref and out parameter variables), and any operation on one variable does not affect another variable.
 In classes, two variables can contain reference of the same object and any operation on one variable can affect another variable.

 In this way, struct should be used only when you are sure that -
  • It logically represents a single value, like primitive types (int, double, etc.).
  • It is immutable.
  • It should not be boxed and un-boxed frequently.

In all other cases, you should define your types as classes.

e.g. Struct

  1. struct Location   
  2. {  
  3.     publicint x, y;  
  4.     publicLocation(int x, int y)  
  5.     {  
  6.         this.x = x;  
  7.         this.y = y;  
  8.     }  
  9. }  
  10. Locationa = new Location(20, 20);  
  11. Locationb = a;  
  12. a.x = 100;  
  13. System.Console.WriteLine(b.x)  
  14. ;  
The output will be 20. Value of "b" is a copy of "a", so "b" is unaffected by change of "a.x". But in class, the output will be 100 because "a" and "b" will reference the same object.

I think, this article clarifies most of the doubts about struct. If you find further queries about struct, please share with me so that everyone can have a clear understanding about this topic.