I am working on a program to display "flash cards." Basically, the flash cards are 2 jpeg files, the front and the back. I'm using them to aid in learning a foreign language. Currently, I have this code: private void btAdd_Click(object sender, EventArgs e) { hpClass blah = new hpClass(); blah.addToArray( tbFrontFile.Text, tbBackFile.Text ); blah.serializeArray( blah, "test.txt" ); } [Serializable] public class hpClass { Stream[,] images; FileStream fsFront; FileStream fsBack; FileStream fsData; BinaryFormatter bfSerial; public void addToArray(string front, string back) { fsFront = new FileStream( front, FileMode.Open ); fsBack = new FileStream( back, FileMode.Open ); images = new Stream[1, 2] { { fsFront, fsBack } }; } public void serializeArray(object anything, string path) { fsData = new FileStream( path, FileMode.Create ); bfSerial = new BinaryFormatter(); bfSerial.Serialize( fsData, anything ); fsData.Close(); } } The error I am getting is this: Type 'System.IO.FileStream' in Assembly 'mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' is not marked as serializable. And the bfSerial.Serialize line is the one generating the error. I'm using the C# 2005 Express Edition Beta. I'm completely lost :( Any suggestions?