Converting byte array to string and back again in C#

So here's the deal: I'm trying to open a file (from bytes), convert it to a string so I can mess with some metadata in the header, convert it back to bytes, and save it. The problem I'm running into right now is with this code. When I compare the string that's been converted back and forth (but not otherwise modified) to the original byte array, it's unequal. How can I make this work?

public static byte[] StringToByteArray(string str)
{
    UTF8Encoding encoding = new UTF8Encoding();
    return encoding.GetBytes(str);
}

public string ByteArrayToString(byte[] input)
{
    UTF8Encoding enc = new UTF8Encoding();
    string str = enc.GetString(input);
    return str;
}

Here's how I'm comparing them.

byte[] fileData = GetBinaryData(filesindir[0], Convert.ToInt32(fi.Length));
string fileDataString = ByteArrayToString(fileData);
byte[] recapturedBytes = StringToByteArray(fileDataString);
Response.Write((fileData == recapturedBytes));

I'm sure it's UTF-8, using:

StreamReader sr = new StreamReader(filesindir[0]);
Response.Write(sr.CurrentEncoding);

which returns "System.Text.UTF8Encoding".