Hi,
I have been trying to understand the workings of viewstate in ch 8.i think i understand that theoretically but then i seemed to not get the workings of it - especially when i attempt the exercise question 2 and modify the code accordingly.
can u please help?

our objective:
1. when the page 1st loads - the AboutUs.aspx will show the banner in left - vertically
thru this code: in Banner.ascx.cs

public Direction DisplayDirection
{
get
{
object displaydirection = ViewState["DisplayDirection"];
if (displaydirection != null)
{
return (Direction)displaydirection;
}
else
{
return Direction.Vertical;
}
}

set
{
ViewState["DisplayDirection"] = value;
}
}

2. if it is a postback:
return (Direction)displaydirection;
would be used.
and besides i think
<Wrox:Banner ID="Banner2" runat="server" DisplayDirection="Horizontal" />
is already set.
so in the subsequent loads the banner is horizontal.

is this what is happening? am i thinking correct??

i would love to get more info on viewstate.
can u please suggest something?

thanks a ton,
sarala

Hi there,

With a normal property (e.g. one not using ViewState) the value would be lost after each post back. Consider this:

if (!Page.IsPostBack)
{
myBanner.NavigateUrl = "SomeUrl";
}

What happens when NavigateUrl is a simple property and the user clicks a button on the page? The following:

1. The page loads
2. Because Page.IsPostBack is not true, the NavigateUrl is set to "SomeUrl"
3. The user clicks a button and posts back
4. Because Page.IsPostBack is now true, the NavigateUrl value is not set. Since it can't keep its own value, the previous value is lost.

When you change the property to a ViewState property, the following happens:

1. The page loads
2. Because Page.IsPostBack is not true, the NavigateUrl is set to "SomeUrl"
3. The user clicks a button and postbacks
4. Because Page.IsPostBack is now true, the NavigateUrl value is not set. However, it stored its value in ViewState in step 2, so it still contains that value.

Does that help?

Imar

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Imar Spaanjaars
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Author of Beginning ASP.NET 4.5 : in C# and VB, Beginning ASP.NET Web Pages with WebMatrix
and Beginning ASP.NET 4 : in C# and VB.
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