What’s the false operator in C# good for?

by

You can use it to override the && and || operators.

The && and || operators can’t be overridden, but if you override |, &, true and false in exactly the right way the compiler will call | and & when you write || and &&.

For example, look at this code (from http://ayende.com/blog/1574/nhibernate-criteria-api-operator-overloading – where I found out about this trick; archived version by @BiggsTRC):

public static AbstractCriterion operator &(AbstractCriterion lhs, AbstractCriterion rhs)
{
       return new AndExpression(lhs, rhs);
}

public static AbstractCriterion operator |(AbstractCriterion lhs, AbstractCriterion rhs)
{
       return new OrExpression(lhs, rhs);
}

public static bool operator false(AbstractCriterion criteria)
{
       return false;
}
public static bool operator true(AbstractCriterion criteria)
{
       return false;
}

This is obviously a side effect and not the way it’s intended to be used, but it is useful.

More Related Contents:

  1. What is the C# Using block and why should I use it? [duplicate]
  2. What are Automatic Properties in C# and what is their purpose?
  3. What does “DateTime?” mean in C#?
  4. Why is Main method private?
  5. What does the @ prefix do on string literals in C#
  6. How to get ALL child controls of a Windows Forms form of a specific type (Button/Textbox)?
  7. Can attributes be added dynamically in C#?
  8. Detect if deserialized object is missing a field with the JsonConvert class in Json.NET
  9. Detect if running as Administrator with or without elevated privileges?
  10. What is the best way to check for Internet connectivity using .NET?
  11. Kill child process when parent process is killed
  12. Remove items from one list in another
  13. Retrieve current URL from C# windows forms application
  14. Icecast 2: protocol description, streaming to it using C#
  15. How can I print the contents of an array horizontally?
  16. Regex that matches a newline (\n) in C#
  17. How do I marshal a struct that contains a variable-sized array to C#?
  18. What is the correct way to compare char ignoring case?
  19. How to implement a singleton in C#?
  20. What value should I pass into TimeZoneInfo.FindSystemTimeZoneById(String)?
  21. Should a property have the same name as its type?
  22. VS2010 – How to automatically stop compile on first compile error
  23. How to check if the system audio is muted?
  24. Are static members of a generic class tied to the specific instance?
  25. How do I find out what directory my console app is running in?
  26. How do I get .NET to garbage collect aggressively?
  27. Get the property name used in a Lambda Expression in .NET 3.5
  28. What event catches a change of value in a combobox in a DataGridViewCell?
  29. What is the “base class” for numeric value types?
  30. Memory usage in C#

Leave a Comment