FoldBack2

Applies a function to corresponding elements of two collections, starting from the end, threading an accumulator argument through the computation.

Parameters	Returns
Func<T, T2, TState, TState> folder IEnumerable<T> source IEnumerable<T2> source2 TState state	TState

Usage

Accumulating the bigger value in the same position of these two collections

//IEnumerable<Animal> source = { 1, 2, 3 }
//IEnumerable<Animal> source2 = { 3, 2, 1 }

int result = 
    source.FoldBack2( 
        source2, 
        (_state, element1, element2) =>
             _state + Math.Max(element1, element2),
        12);

//result = 20

When the type of elements in your collection are: int, decimal, double, string or bool you can also use this function combined with the Operations described in operations section as folder functions.

Using an operation as a folder

//IEnumerable<int> source = { 2, 3, 5, 0 }
//IEnumerable<int> source2 = { 3, 2, 0, 5 }

source.FoldBack2(source2, IntegerOperations.Add3, 30);

//result = 50