What is Predicate<T>?

Simply put it is a delegate which is looking for a method that accepts one parameter and returns true or false.

It is used by several methods in .Net Framework mostly in List<T> and Array.

for example ,If you have a list of Person class and try to find out who is less than 30

public class Person

{

public string Name { get; set; }

public int Age { get; set; }

}

var persons = new List<Person>()

{

new Person(){Name="azadeh",Age=30},

new Person(){Name="elham",Age=30},

new Person(){Name="maryam",Age=31},

new Person(){Name="asal",Age=28},

new Person(){Name="arezoo",Age=27},

};

You will see that all of them return a same result.

var inTwenties1 = persons.FindAll(x => x.Age < 30);

var inTwenties2 = persons.FindAll(Test);

var inTwenties3 = persons.FindAll(delegate(Person p) { return p.Age < 30; });

public static bool Test(Person p)

{

return p.Age < 30;

}

Predicate <T> or Func<T, bool>?

These two are exactly same. The only difference is that Predicate is older than Func<T, bool>.

Azadeh Khojandi