Classes can do the same job as C# structs - so why both? Find out in this extract from my new book, Deep C#:Dive Into Modern C#.

Deep C#

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 Chapter List

1. Why C#?
   
   I Strong Typing & Type Safety
2. Strong Typing
      Extract  Why Strong Typing
3. Value & Reference
4.    Extract Value And Reference
5. Structs & Classes
      Extract Structs & Classes 
6. Inheritance
      Extract Inheritance
   
7. Interfaces & Multiple Inheritance
      Extract Interface
   
8. Controlling Inheritance
   II Casting & Generics
9. Casting - The Escape From Strong Typing
      Extract Casting I ***NEW!
   
10. Generics
11. Advanced Generics
12. Anonymous & Dynamic
    Typing III Functions
13. Delegates
14. Multicast Delegates
15. Anonymous Methods, Lambdas & Closures
    IV Async
16. Threading, Tasks & Locking
17. The Invoke Pattern
18. Async Await
19. The Parallel For
    V Data - LINQ, XML & Regular Expressions
20. The LINQ Principle
21. XML
22. LINQ To XML
23. Regular Expressions
    VI Unsafe & Interop
24. Interop
25. COM
26. Custom Attributes
27. Bit Manipulation
28. Advanced Structs
29. Pointers 

Extra Material

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Most languages have something like the C# struct – they may call it something different, often a “record”, but the idea is the same. A struct is a collection of different data types with each data type beginning identified as a “field” – similar to a name and address card or record. C# has structs but they play a deeper role in the language being more like classes than the simple data structures they are in other languages.

Structs Are Value Types

Although value types are often introduced as “simple” types such as int or float, all value types are really just examples of struct which is generally thought of as a more complicated type with multiple values as fields.

The simple value types are structs, but they are also treated differently to avoid the overheads a genuine struct brings with it to make sure that your program runs efficiently. The fact that an int is a struct really only has an impact on your programs because this means that int inherits a set of simple standard methods from object. For example, it is perfectly OK to write:

int a;
string b = a.ToString();

In fact, int is just an alias for the System.Int32 struct and you could write:

System.Int32 a;

in place of int a, but it is usual not to. We will return to the issue of simple data types as objects later in this chapter because there is a little more to it.

It is reasonable to say that the most important division in the C# type system is the split into classes and structs (both descended from object). And the really big difference between the two is that class is a reference type whereas struct is a value type.

Structs are from value and classes are from reference

In many cases you have the choice of implementing something either as a class or a struct. For example consider a simple type designed to store the x,y coordinates of a point.

You can do this as a class:

class PointR
{
  public int x,y;
}

or as a struct:

struct PointV
{
  public int x,y;
}

Notice that the class is named with a trailing R for Reference and the struct with a trailing V for value.

The most important difference is due to the fact that a struct is a value type and a class is a reference type. That is, the class behaves as described earlier for general reference types and struct behaves like a general value type.