IEnumerable<T>.Contains with predicate

Question

I need just to clarify that given collection contains an element.

I can do that via collection.Count(foo => foo.Bar == "Bar") > 0) but it will do the unnecessary job - iterate the whole collection while I need to stop on the first occurrence.

But I want to try to use Contains() with a predicate, e.g. foo => foo.Bar == "Bar".

Currently IEnumerable<T>.Contains has two signatures:

• IEnumerable<T>.Contains(T)

• IEnumerable<T>.Contains(T, IEqualityComparer<T>)

So I have to specify some variable to check:

var collection = new List<Foo>() { foo, bar }; collection.Contains(foo); 

or write my custom IEqualityComparer<Foo> which will be used against my collection:

class FooComparer : IEqualityComparer<Foo> {     public bool Equals(Foo f1, Foo f2)     {         return (f1.Bar == f2.Bar); // my predicate     }      public int GetHashCode(Foo f)     {         return f.GetHashCode();     }    } 

So are there any other methods to use predicate?

Answer 1

.Any(predicate) 

sounds like what you want; returns bool, returning true as soon as a match is found, else false. There is also:

.All(predicate) 

which behaves in a similar way, returning false as soon as a non-match is found, else true.