How to read byte array into FileStream

I have an byte array and I want to read the byte array into a FileStream. Below is my sample of code:

string fileName = "test.txt";
byte[] file = File.ReadAllBytes(Server.MapPath("~/Files/" + fileName));
FileStream fs = new FileStream();
fs.ReadByte(file);
object obj = LoadFile<object>(fs);

public static T LoadFile<T>(FileStream fs)
{
    using (GZipStream gzip = new GZipStream(fs, CompressionMode.Decompress))
    {
        BinaryFormatter bf = new BinaryFormatter();
        return (T)bf.Deserialize(gzip);
    }
}

In the method above, I have use FileStream to read byte array, but unlucky fs.ReadByte cannot read byte array. Any help please focus on how to Read byte array into a FileStream for using as a parameter in method "LoadFile". Please do not read directly the file into FileStream because the file here is loaded from somewhere else like from database or other source.