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

Extra Material
Passing Parameters ***NEW!

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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.