This article is right for those who are searching for the most elegant way to implement Fibonacci Range Algorithm in C#.
Several days I was trying following variations:

• Recursive
• Recursive with TPL
• Matrices exponential
• Matrices exponential with TPL
• Clean LINQ
• Complicated formulas
• Parallelized LINQ
• Iterative
• Iterative with TPL
• Iterative with yield return

The last one has shown itself absolutely outstanding in both simplicity and performance in selection entire range and certain element. Keeping this algorithm simple allows CLR optimizing it in a way much enough to come over others. This function is all the stuff needed:

public static IEnumerable<Int64> GetFibonacciRange(UInt32 steps)
{
    for (Int64 i = 0, previous = -1, next = 1, sum = 0; i < steps; ++i)
    {
        sum = previous + next;
        previous = next;
        yield return next = sum;
    }
}

And some samples of using it:

//Get first 5 numbers of sequence
GetFibonacciRange(5); //0 1 1 2 3
//Get first 8 numbers of sequence beginning from 1
GetFibonacciRange(9).Skip(1).Take(8); // 1 1 2 3 5 8 13 21
//Get the 15th number of sequence
GetFibonacciRange(15).Last(); //377
//OR
GetFibonacciRange(20).ElementAt(15 - 1); //377