Error - is not marked as serializable

The error I'm getting is: ``` Type 'OrgPermission' in Assembly 'App_Code.ptjvczom, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' is not marked as serializable. ``` here is my code: I have a gridview, that uses the following DataSource: ``` <asp:ObjectDataSource ID="ObjectDataSource1" runat="server" SelectMethod="GetOrgList" TypeName="Org"> <SelectParameters> <asp:SessionParameter Name="orgCodes" SessionField="UserOrgs" Type="Object" /> <asp:Parameter DefaultValue="Y" Name="active" Type="String" /> </SelectParameters> </asp:ObjectDataSource> ``` I set the session variable in my page load like so: ``` User cUser = new User(userid); //make sure the user is an Admin List<OrgPermission> orgs = new List<OrgPermission>(); foreach(OrgPermission org in cUser.orgs) { if (org.type=='admin') { orgs.Add(org); } } Session["UserOrgs"] = orgs; ``` My user class looks like this: ``` public class OrgPermission { public string Org { get; set; } public List<string> type { get; set; } public OrgPermission() { } } public class cUser { public string userid { get; set; } public List<OrgPermission> orgs { get; set; } public clsUser(string username) { //i set everything here } } ``` I can't understand why it's breaking, can I use it without making it serializable? I tried to debug, and the session variable sets just fine, it then goes into the GetOrgList and returned correct results, but the page does not load and I get the error above. Here is a snippet of my GetOrgList function: ``` public DataTable GetOrgList(List<OrgPermission> orgCodes, string active) { string orgList = null; //code to set OrgList using the parameter is here. DataSet ds = new DataSet(); SqlConnection conn = new SqlConnection(cCon.getConn()); SqlCommand cmd = new SqlCommand("sp_GetOrgList", conn); cmd.CommandType = CommandType.StoredProcedure; cmd.Parameters.Add(new SqlParameter("@orgList", orgList)); cmd.Parameters.Add(new SqlParameter("@active", active)); conn.Open(); SqlDataAdapter sqlDA = new SqlDataAdapter(); sqlDA.SelectCommand = cmd; sqlDA.Fill(ds); conn.Close(); return ds.Tables[0]; } ```