c# - 配列に追加できません

Question

私は配列のチュートリアルに取り組んでいます。配列に関する私の知識は限られています。「演算子 '+=' はタイプ 'double[]' のオペランドに適用できません。これが機能しない理由がわかりません。チュートリアルで配列を使用して変更するように要求されるまで、元のコードは正しく機能していました。アイデア？

配列のない元のコード:

string inputString;
        double sales=0, totalA = 0, totalB = 0, totalC=0;
        double total = 0;
        string initial;

        Console.Write("Enter family initial: ");
        inputString = Console.ReadLine();
        initial = inputString.ToString();

        while (initial != "z" && initial != "Z")
        {
            Console.Write("Enter a sales amount: ");
            inputString = Console.ReadLine();
            sales = Convert.ToDouble(inputString);
            total += sales;

            if (initial == "A")
            {
                totalA += sales;
            }
            else if (initial == "B")
            {
                totalB += sales;
            }
            else if (initial == "C")
            {
                totalC += sales;
            }


            Console.Write("Enter family initial: ");
            inputString = Console.ReadLine();
            initial = inputString.ToString();

        }
        Console.WriteLine("Family A earned: {0}", totalA.ToString("C"));
        Console.WriteLine("Family B earned: {0}", totalB.ToString("C"));
        Console.WriteLine("Family C earned: {0}", totalC.ToString("C"));
        Console.WriteLine("Grand Total Sales: {0}",total.ToString("c"));

これは、コードを (要求ごとに) 変更して、イニシャルと累計販売額を配列に格納する試みです。それを達成するために私ができることのアイデアはありますか?

string inputString;
// double sales=0, totalA = 0, totalB = 0, totalC=0;
double sales;
double total = 0;
string initial;

string[] familyNames = {"Anderson","Bowman","Claxton"};
string[] inital = { "A", "B", "C" };
double[] totalA, totalB, totalC;

Console.Write("Enter family initial: ");
inputString = Console.ReadLine();
initial = inputString.ToString();

while (initial != "z" && initial != "Z")
{
    Console.Write("Enter a sales amount: ");
    inputString = Console.ReadLine();
    sales = Convert.ToDouble(inputString);
    total += sales;




    if (initial == "A")
    {
        totalA += sales;
    }
    else if (initial == "B")
    {
        totalB += sales;
    }
    else if (initial == "C")
    {
        totalC += sales;
    }


    Console.Write("Enter family initial: ");
    inputString = Console.ReadLine();
    initial = inputString.ToString();

}
Console.WriteLine("Family A earned: {0}", totalA.ToString("C"));
Console.WriteLine("Family B earned: {0}", totalB.ToString("C"));
Console.WriteLine("Family C earned: {0}", totalC.ToString("C"));
Console.WriteLine("Grand Total Sales: {0}",total.ToString("c"));