Exists

Returns true if the given predicate functions return true when applied to either value. Otherwise, returns false.

Parâmetros	Retorno
Func<TRight, bool> predicateWhenRight Func<TLeft, bool> predicateWhenLeft Either<TLeft, TRight> either	bool

Usage

When the Either IsLeft, the result will be the return of predicateWhenLeft function, otherwise will be the return of predicateWhenRight.

When Either IsRight and predicate returns true

Either<string, int> either = 20;
bool result = 
    either.Exists(
        right => right == 20,
        left => left == "Hello World");

//result = true

When Either IsLeft and predicate returns true

Either<string, int> either = "Hello World";
bool result = 
    either.Exists(
        right => right == 20,
        left => left == "Hello World");

//result = true

When Either IsRight and predicate returns false

Either<string, int> either = 15;
bool result = either.Exists(
right => right == 20,
left => left == "Hello World");
//result = false

One sided approach

You can also use the ExistsLeft and ExistsRight to produce the same results, but with these methods the predicated is applied just to one of the possible values.

When the target type is different from Either current value the result always will be false

ExistsRight when Either IsRight

Either<string, int> either = 20;
bool result = either.ExistsRight(right => right == 20);

//result = true

ExistsLeft when Either IsRight

Either<string, int> either = 20;
bool result = either.ExistsLeft(left => left == "Hello World");

//result = false