101 LINQ Samples: Custom Sequence Operators

Combine

This sample calculates the dot product of two integer vectors. It uses a user-created sequence operator, Combine, to calculate the dot product, passing it a lambda function to multiply two arrays, element by element, and sum the result.

public static class CustomSequenceOperators
{
    public static IEnumerable Combine(this IEnumerable first, IEnumerable second, 
    Func func) {
        using (IEnumerator e1 = first.GetEnumerator(), e2 = second.GetEnumerator())
        {
            while (e1.MoveNext() && e2.MoveNext()) {
                yield return func(e1.Current, e2.Current);
            }
        }
    }
}

public void Linq98() {            
    int[] vectorA = { 0, 2, 4, 5, 6 };
    int[] vectorB = { 1, 3, 5, 7, 8 };
    
    int dotProduct = vectorA.Combine(vectorB, (a, b) => a * b).Sum();
    
    Console.WriteLine("Dot product: {0}", dotProduct);
}

Result

Dot product: 109