Hey, i did google but still not able to understand why am I not able to do it. Also, I have a doubt, if am doing some thing like this(code below) in a normal project(not an excel addin),this is working fine: emp[] e = { new emp(1,"Mark",5000), new emp(2,"Mich",6000), new emp ( 3, "Amol", 4460 ), new emp ( 4, "Anil", 9456 ), new emp ( 5, "Srikanth", 9500 ), }; //SERIALIZING PART Stream s = File.Open("c:\\New Folder\\emp.txt", FileMode.Create,FileAccess.ReadWrite); BinaryFormatter b = new BinaryFormatter(); b.Serialize(s, e); s.Close(); //DESERIALIZING PART s = File.Open("c:\\New Folder\\emp.txt", FileMode.Open, FileAccess.ReadWrite); emp[] ee = (emp[])b.Deserialize(s); foreach (emp ez in ee) MessageBox.Show(ez.ToString()); s.Close(); But, the same is not working when am introducing this piece of code in my excel-addin project. What could be the reason for this behavour?! Thanks.