Serialize .NET objects to store and retrieve them from a file or viewstate in ASP.NET

Everything is .NET is an object. But sometimes you need to store an object to a file, ASP.NET's viewstate etc. then get it back from the file or viewstate and continue to use it as the object it originally was.

The process of doing this in .NET is called serialization. Serializing an object is like deflating it. Once it is serialized it can be written out to a stream such as a file. Then, it can be read back in and de-serialized or inflated and used just like it was stored in memory the entire time.

Why else serialize an object? Suppose we have a PayeeData object that has no methods but holds all the data for a particular payee. If we want to save all the payee's data across multiple requests for the same ASP.NET web page, we can add the PayeeData object to the page's viewstate. But to do this it must first be serialized.

.NET lets you serialize an object simply be decorating its class with a serializable attribute. After that, .NET handles everything for you.

Making a class serializable in VB.NET:

   <Serializable()> _
      Public Class PayeeData
         ...
      End Class

Making a class serializable in C#:

   [Serializable]_
      public class PayeeData
      {
         ...
      }

Another example. Say you log errors in your application then display them on a web page. You can create a LogEntry object to hold the error information.

Serializable LogEntry class using VB.NET:

   <Serializable()> _
    Public Class LogEntry
        Private _EntryDate As String = ""
        Private _EntryTime As String = ""
        ...
        Public Property EntryDate() As String
            Get
                Return _EntryDate
            End Get
            Set(ByVal Value As String)
                _EntryDate = Value
            End Set
        End Property
        ...
   End Class

In your application you can collect error info by populating the LogEntry object with information on each error and store these entries in an array.

   Dim aryEntryList As ArrayList = New ArrayList
   Entry = New LogEntry
   Entry.EntryDate = ...
   Entry.EntryTime = ...
   ...
   aryEntryList.Add(Entry)

Now you have a list of errors and you want to display them. You can use a Repeater control on your ASP.NET web page.

HTML snippet showing Repeater control:

   <TABLE>
      <asp:Repeater id="LogRepeater" runat="server">
         <ItemTemplate>
            <TR><TD>
               Entry Date: <%# DataBinder.Eval(Container.DataItem, "EntryDate") %><br>
               Entry Time: <%# DataBinder.Eval(Container.DataItem, "EntryTime") %>
               ...
            </TD></TR>
         </ItemTemplate>
      </asp:Repeater>
   </TABLE>

The Repeater control gets bound to a datasource and repeats the HTML code for each entry in the datasource. To understand the DataBinder.Eval statement, see my DataBinder page. So, back to serialization. We can use the aryEntryList array of errors as our datasource for the Repeater control provided it is serializable.

   LogRepeater.DataSource = aryEntryList
   LogRepeater.DataBind()