C#

public class BinaryEncoder
{
	public static int[] bitValues = new int[8]{128,64,32,16,8,4,2,1};

	/// <summary>
	/// Creates a bytearray with the ones and zeroes from a given string
	/// </summary>
	/// <param name="stringToEncode">The string to convert to a binary array</param>
	/// <returns>The ones and zeroes in a bytearray</returns>
	public static byte[] StringToBinary(string stringToEncode)
	{
		//make a bytearray 8 times the size of the string to encode
		byte[] bytes = new byte[stringToEncode.Length * 8];
		//create two temporary countervariables
		int byteOffset = 0;
		int byteIndex = 0;

		//for each character in the string
		for(int charCounter = 0; charCounter< stringToEncode.Length; charCounter++)
		{
			//find the basic byteoffset by multiplying the character's position by eight
			//basically how far should we start inside the bytearray, when adding the bits
			//from another character
			byteOffset = charCounter*8;

			//now for each bit in the character
			for (int bitCounter = 0; bitCounter < 8; bitCounter++)
			{
				//find the specific place in the bytearray
				byteIndex = byteOffset + bitCounter;
				//if there is a 1-bit inside the character at the specified place
				if((stringToEncode[charCounter] & bitValues[bitCounter]) != 0)
					bytes[byteIndex] = 1;	//then we store a 1 in the bytearray
				else
					//otherwise we store a zero
					bytes[byteIndex] = 0;
			}
		}
		//return the created array
		return bytes;
	}
}