WorkflowApplication generate unhandle exception in ASP.NET

am using simple persistence workflow application in ASP.NET when i try start workflow using WorkflowApplication invoker the .NET framework generate unhandled exception.

the exception is:

Type 'VacationRe开发者_StackOverflow社区questWorkflow.VacationRequestModel' in Assembly 'VacationRequestWorkflow, Version=1.0.0.0, Culture=neutral, PublicKeyToken=84fad1a74027a4c8' is not marked as serializable.

i used

ActivityXamlServices.Load(
                ActivityXamlServices.CreateReader(
                    new XamlXmlReader("*XAML path*",
                        new XamlXmlReaderSettings { LocalAssembly = Assembly.GetExecutingAssembly() })));

to resolve this issue but didn't work.

please advice.

Maybe I'm missing something, but isn't this as simple as marking your class Serializable, using the Serializable attribute?