Deserializing a byte array

If I wanted to fill a structure from a binary file, I would use something like this:

using (BinaryReader br = new BinaryReader(File.Open(filename, FileMode.Open)))
{
    myStruct.ID = br.ReadSingle();
    myStruct.name = br.ReadBytes(20);
}

However, I must read the whole file into a byte array before deserializing, because I want to do some pre-processing. Is there any managed way to fill my structure from the byte array, preferably similar to the one above?