• ​Inherited by default by all the types created

• ​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

• ​MemberwiseClone() - reates a shallow copy of the current object

• static
  • ReferenceEquals() - determines whether the specified object instances are the same instance
• instance
  • GetType() - gets the type of the current instance.

• Compares the addresses for reference types
• Or the binary representation for value types

• You can override Equals() and use its implementation for == and !=

• Checks if an object is an instance of some type
• Polymorphic operation
  • 5 is Int
  • 5 is object
  • 5 is IComparable<int>

• Casts a reference type to another reference type
• Returns null value if it fails
  • E.g. if the types are incompatible

• 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

• 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

• 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