C# Common Type System
Telerik Academy Alpha

 

 Table of contents

Object, is, as, yield, ref, out

System.Object

 C# Types

 Object class

  • Base class for each .NET type
    • ​Inherited by default by all the types created
  • ​Provides a few virtual methods which are useful for certain tasks
    • ​Equals() - compare with other object
    • ToString() - represents the object as a string
    • GetHashCode() - provides this hash code for algorithms that need quick checks of object equality
    • Finalize() - allows an object to try to free resources and perform other cleanup operations

 

 Object class

  • ​Provides protected method which can be used only inside class definition
  • Provides two public methods
    • static
      • ReferenceEquals() - determines whether the specified object instances are the same instance
    • instance

 

 Override virtual methods

  • By default the operator == calls the ReferenceEquals() method
    • Compares the addresses for reference types
    • Or the binary representation for value types
  • The methods Equals(), GetHashCode() should be defined at the same time to be sure that the the two objects are going to be compared correctly
  • The same applies for the operators == and !=
    • You can override Equals() and use its implementation for == and !=

 

Type operators

 is and as operators

  • The is operator
    • Checks if an object is an instance of some type
    • Polymorphic operation
      • 5 is Int
      • 5 is object
      • 5 is IComparable<int>
  • The as operator
    • Casts a reference type to another reference type
    • Returns null value if it fails
      • E.g. if the types are incompatible

Live Demo

 Live Demo

yield return

 yield return

  • The yield return construct in C# simplifies the IEnumerator<T> implementations
    • When a yield return statement is reached
      • The expression is returned, and the current location in code is retained (for later use)

  • Populating a temporary list is like downloading the whole video, whereas using yield is like streaming that video.

  • If you have expensive operation you can stream the data, instead of waiting for the completion

 yield return

  • Run the example below in Visual Studio because it doesn't work as expected here

ref and out

 Passing parameters

  • Parameters can be passed in several ways to the methods:
    • in (default)
      • Passing value for value types
      • Passing heap address for reference types
    • out
      • Passed by stack address for both value types and reference types
      • The initialization can be done by the called method

 Passing parameters

  • Parameters can be passed in several ways to the methods:
    • ref
      • Passed by stack address for both value types and reference types
      • Initialization can't be done by the called method – access is for read and write

 Passing parameters

Questions?

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