char[] znaky = new char[moje.Length];
for (int i = 0; i < znaky.Length; i++)
{
    znaky[i] = moje[i];
}

string binary = "";
foreach (int a in znaky)
{
    binary += Convert.ToString(znaky[a], 2);
}

for (int a = 0; a < znaky.Length; a++)

Convert.ToString(a, 2);