A predicate is a function that returns
true or
false & a predicate delegate is a reference to a predicate.
So basically a predicate delegate is a reference to a function that returns
true or
false. Predicates are very useful for filtering a list of values - here is an example.
using System;
using System.Collections.Generic;
class Program
{
static void Main()
{
List list = new List { 1, 2, 3 };
Predicate predicate = new Predicate(greaterThanTwo);
List newList = list.FindAll(predicate);
}
static bool greaterThanTwo(int arg)
{
return arg > 2;
}
}
Now if you are using C# 3 you can use a lambda to represent the predicate in a cleaner fashion:
using System;
using System.Collections.Generic;
class Program
{
static void Main()
{
List list = new List { 1, 2, 3 };
List newList = list.FindAll(i => i > 2);
}
}
OR use the plane old inline Function delegate:
using System;
using System.Collections.Generic;
class Program
{
static void Main()
{
List list = new List { 1, 2, 3 };
List newList = list.FindAll(delegate(int arg)
{
return arg> 2;
});
}
}
