Question

Consider a web form (aspx) wth an associated codefile (aspx.cs).

In the codefile, for instance, we have the following:

public partial class MyPage : System.Web.UI.Page {

   int myint;
   string mystring;

   public void Page_Load(object sender, EventArgs e) {
      ...
      if (!this.IsPostBack) {
         this.myint = 2;
         this.mystring = "Hello";
      }
      ...
   }

}

Can I expect to have the two variables everytime the page is posted back? I mean: are page class fields kept as part of the web form state?

Thankyou

Answer 1

No, these objects would be disposed at the end of the Page-Lifecycle.
If you want to persist them in ViewState you have to add them to it.

Objects that need to be stored in ViewState must be serializable.

Storing Simple Data Types in the ViewState

Like most types of state management in
ASP.NET, view state relies on a
dictionary collection, where each item
is indexed with a unique string name.
For example, consider this code:

ViewState["ViewStateVariableName"] = 1;

This places the value 1 (or rather, an
integer that contains the value 1)
into the ViewState collection and
gives it the descriptive name
ViewStateVariable. If there is
currently no item with the name
ViewStateVariable, a new item will be
added automatically. If there is
already an item indexed under this
name, it will be replaced.

You can access this variable anywhere
within the page/control where the
viewstate variable has been added.
When retrieving a value, you use the
key name.

int number = (int) ViewState["ViewStateVariable"];

You also need to cast the retrieved
value to the appropriate data type.
This is because the ViewState
collection stores all items as generic
objects which also give you the
flexibility to store any type of basic
data types in it. In fact, you can
even store your custom objects in the
view state.

Storing Objects in View State

You can store your own objects in view
state just as easily as you store
numeric and string types. However, to
store an item in view state, ASP.NET
must be able to convert it into a
stream of bytes so that it can be
added to the hidden input field in the
page. This process is called
serialization. If your objects aren’t
serializable (and by default they
aren’t), you’ll receive an error
message when you attempt to place them
in view state.

• http://www.beansoftware.com/ASP.NET-Tutorials/ViewState-In-ASP.NET.aspx
• http://msdn.microsoft.com/en-us/magazine/cc188774.aspx