Predicate delegate type in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Predicate delegate in C#?

A Predicate delegate is a special type of delegate that represents a method that takes one input parameter and returns a boolean value (true or false). It is often used to test conditions.

beginner

How do you declare a Predicate delegate for integers?

You declare it as Predicate<int>. For example: Predicate<int> isEven = x => x % 2 == 0; This means isEven is a method that checks if an integer is even.

beginner

What is the return type of a Predicate delegate method?

The return type is always bool. It returns true if the condition is met, otherwise false.

intermediate

Can Predicate delegates be used with List<T> methods? Give an example.

Yes, Predicate delegates are commonly used with List<T> methods like Find or RemoveAll. Example: list.RemoveAll(x => x < 0); removes all negative numbers from the list.

intermediate

What is the difference between Predicate<T> and Func?

Predicate<T> is a delegate specifically for methods that take one parameter and return bool. Func can do the same but is more general and can have multiple parameters. Predicate<T> is clearer when you want a boolean test.

What does a Predicate delegate return?

A int

B string

C bool

D void

A Predicate delegate always returns a boolean value (true or false).

Which of these is a valid Predicate declaration for strings?

A Predicate<string> isEmpty = s => s.Length == 0;

B Predicate<string> isEmpty = s => s + "";

C Predicate<string> isEmpty = s => Console.WriteLine(s);

D Predicate<string> isEmpty = s => s.Length;

Predicate must return a bool. s => s.Length == 0 returns true if the string is empty.

Which List<T> method commonly uses Predicate<T>?

A Add

B Find

C Sort

D Clear

List.Find uses a Predicate to locate the first element matching the condition.

What parameter count does a Predicate delegate accept?

A One

B Multiple

C Two

D Zero

Predicate delegates accept exactly one input parameter.

Which is a key difference between Predicate<T> and Func?

A Predicate<T> returns int, Func<T, bool> returns bool

B Predicate<T> is a class, Func<T, bool> is a delegate

C Predicate<T> can only be used with strings

D Predicate<T> only takes one parameter, Func<T, bool> can take multiple

Predicate takes one parameter and returns bool; Func can take multiple parameters and returns bool.

Explain what a Predicate delegate is and how it is used in C#.

Think about how you test conditions with a method that returns true or false.

Describe the difference between Predicate and Func delegates.

Focus on parameter count and clarity of intent.