在将相当大的数字从二进制转换为十进制时遇到困难

我正在将二进制数转换为十进制数，直到我的数字似乎超过$2^64$。这似乎是因为数据类型不能容纳大于2^64的数字，明白了吗?发生的事情是，存储在我的base_2变量的数字似乎不能超过$2^64$，因为它应该处理巨大的二进制数，但它溢出，因为数据类型太小，重置为0…有什么办法能让我绕过或解决这个问题吗?

        //Vector to store the Binary # that user has input
        List<ulong> binaryVector = new List<ulong>();
        //Vector to store the Decimal Vector I will output
        List<string> decimalVector = new List<string>();
        //Variable to store the input
        string input = "";
        //Variables to do conversions
        ulong base2 = 1;
        ulong decimalOutput = 0;
        Console.WriteLine("2^64=" + Math.Pow(2.00,64));
        //Prompt User
        Console.WriteLine("Enter the Binary Number you would like to convert to decimal: ");
        input = Console.ReadLine();
        //Store the user input in a vector
        for(int i = 0; i < input.Length; i++)
        {
            //If we find a 0, store it in the appropriate vector, otherwise we found a 1..
            if (input[i].Equals('0'))
            {
                binaryVector.Add(0);
            }
            else
            {
                binaryVector.Add(1);
            }
        }
        //Reverse the vector
        binaryVector.Reverse();
        //Convert the Binary # to Decimal
        for(int i = 0; i < binaryVector.Count; i++)
        {
            //0101 For Example: 0 + (0*1) = 0 Thus: 0 is out current Decimal
            //While our base2 variable is now a multiple of 2 (1 * 2 = 2)..
            decimalOutput = decimalOutput + (binaryVector[i] * base2);
            base2 = base2 * 2;
            Console.WriteLine("'nTest base2 Output Position[" + i + "]::" + base2);
        }
        //Convert Decimal Output to String
        string tempString = decimalOutput.ToString();