C# :: Store Each Char Of A String Into Byte-array?

I am trying to store each char of a string(string a ="1100") into a byteArray ( byte[] byteArray = new byte[4]. its not showing any error but its storing like below:

byteArray[0] = 49
byteArray[1] = 49
byteArray[2] = 48
byteArray[3] = 48

and what i want is

byteArray[0] = 1
byteArray[1] = 1
byteArray[2] = 0
byteArray[3] = 0

I don't know why but its replacing 1 with 49 and 0 with 48.what am I doing wrong or how to do this?

my code is as below

byte[] byteArray = new byte[4];)/>
int binArrayAdd = 0;
string a ="1100";
foreach (char Character in a)
{
byteArray [binArrayAdd] = Convert.ToByte(Character);
binArrayAdd++;
}