[c#] How to Fill an array from user input C#?

It made a lot more sense to add this as an answer to arin's code than to keep doing it in comments...

1) Consider using decimal instead of double. It's more likely to give the answer the user expects. See http://pobox.com/~skeet/csharp/floatingpoint.html and http://pobox.com/~skeet/csharp/decimal.html for reasons why. Basically decimal works a lot closer to how humans think about numbers than double does. Double works more like how computers "naturally" think about numbers, which is why it's faster - but that's not relevant here.

2) For user input, it's usually worth using a method which doesn't throw an exception on bad input - e.g. decimal.TryParse and int.TryParse. These return a Boolean value to say whether or not the parse succeeded, and use an out parameter to give the result. If you haven't started learning about out parameters yet, it might be worth ignoring this point for the moment.

3) It's only a little point, but I think it's wise to have braces round all "for"/"if" (etc) bodies, so I'd change this:

for (int counter = 0; counter < 6; counter++)
    Console.WriteLine("{0,5}{1,8}", counter, array[counter]);

to this:

for (int counter = 0; counter < 6; counter++)
{
    Console.WriteLine("{0,5}{1,8}", counter, array[counter]);
}

It makes the block clearer, and means you don't accidentally write:

for (int counter = 0; counter < 6; counter++)
    Console.WriteLine("{0,5}{1,8}", counter, array[counter]);
    Console.WriteLine("----"); // This isn't part of the for loop!

4) Your switch statement doesn't have a default case - so if the user types anything other than "yes" or "no" it will just ignore them and quit. You might want to have something like:

bool keepGoing = true;
while (keepGoing)
{
    switch (answer)
    {
        case "yes":
            Console.WriteLine("===============================================");
            Console.WriteLine("please enter the array index you wish to get the value of it");
            int index = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("===============================================");
            Console.WriteLine("The Value of the selected index is:");
            Console.WriteLine(array[index]);
            keepGoing = false;
            break;

        case "no":
            Console.WriteLine("===============================================");
            Console.WriteLine("HAVE A NICE DAY SIR");
            keepGoing = false;
            break;

        default:
            Console.WriteLine("Sorry, I didn't understand that. Please enter yes or no");
            break;
    }
}

5) When you've started learning about LINQ, you might want to come back to this and replace your for loop which sums the input as just:

// Or decimal, of course, if you've made the earlier selected change
double sum = input.Sum();

Again, this is fairly advanced - don't worry about it for now!