[DotNetDevelopment] From hexadecimal to bit (4 bit format)

[Antony]

Hi everybody,
I have to convert a string (mem) into binary code. Example:
1234A --> 00010010001101001010

I wrote this code, but doesn't work:

string binary = "";
            for (int i = 0; i < mem.Length; i++)
            {
                string s = mem.Substring(i,1);
                binaryString += hex2binary(s);
            }

string hex2binary(string hexvalue)
        {
            string binaryval = "";
            string tmp = Convert.ToString(Convert.ToInt32(hexvalue,
16), 2);
            binaryval = String.Format("{0:X4}", tmp);
            return binaryval;
        }

Thanks for reply!