Convert an integer to a binary string with leading zeros

Question

I need to convert int to bin and with extra bits.

string aaa = Convert.ToString(3, 2);

it returns 11, but I need 0011

Answer 1

public static String HexToBinString(this String value)
{
        String binaryString = Convert.ToString(Convert.ToInt32(value, 16), 2);
        Int32 zeroCount = Convert.ToInt32(Math.Ceiling(Convert.ToDouble(binaryString.Length) / 8)) * 8;

        return binaryString.PadLeft(zeroCount, '0');
}