convert string to binary and overhand

public string Encode(string str)
{
   byte[] encbuff = System.Text.Encoding.UTF8.GetBytes(str);
   return Convert.ToBase64String(encbuff);
}
public string Decode(string str)
{
   byte[] decbuff = Convert.FromBase64String(str);
   return System.Text.Encoding.UTF8.GetString(decbuff);
}

string str = "Hello";
byte []arr = System.Text.Encoding.ASCII.GetBytes(str);

string result = string.Empty;
foreach(char ch in yourString)
{
   result += Convert.ToString((int)ch,2);
}

public string ConvertStringToHex(string asciiString)
{
    string hex = "";
    foreach (char c in asciiString)
    {
        int tmp = c;
        hex += String.Format("{0:x2}", (uint)System.Convert.ToUInt32(tmp.ToString()));
    }
    return hex;
}

public string ConvertHexToString(string HexValue)
{
    string StrValue = "";
    while (HexValue.Length > 0)
    {
        StrValue += System.Convert.ToChar(System.Convert.ToUInt32(HexValue.Substring(0, 2), 16)).ToString();
        HexValue = HexValue.Substring(2, HexValue.Length - 2);
    }
    return StrValue;
}