variable scope and persistence

[Cole Trickle]

Hello...
I assign a variable from the querystring to a class level private variable
as follows

public class CrsInstnc : System.Web.UI.Page {
private string tcoRef = "";

private void Page_Load(object sender, System.EventArgs e) {
if(!IsPostBack){
if(Request.QueryString["ref"] != null){
this.tcoRef = Request.QueryString["ref"].ToString();
}
...
}
}

Every time the page posts back to itself the variable this.tcoRef is empty.
Am I doing something wrong? When the page posts back to itself does the
whole class start from scratch? Should I store the information elsewhere?
Thanks

 

[Eliyahu Goldin]

Every time the page posts back to itself the variable this.tcoRef is
empty.

Am I doing something wrong? When the page posts back to itself does the
whole class start from scratch?

Exactly, this is how web applications work.

Should I store the information elsewhere?

Yes, in a session variable.

Eliyahu

 

[=?ISO-8859-1?Q?=22Anders_Nor=E5s_=5BMCAD=5D=22?=]

Every time the page posts back to itself the variable this.tcoRef is empty.
Am I doing something wrong? When the page posts back to itself does the
whole class start from scratch? Should I store the information elsewhere?

The class is not persisted between postbacks. You must store the value
in either the session state or in the page's view state to persist it
between postbacks.

To stor a value in and retrieve it from the session state do this (C#):
if (Page.IsPostBack) {
// Read from session state
myString=(string) Session["MyValue"];
} else {
// Store in session state
Session["MyValue"] = myString;
}

To store a value in and retrieve it from the view state do this (C#):
if (Page.IsPostBack) {
// Read from view state
myString=(string) ViewState["MyValue"];
} else {
// Store in view state
ViewState["MyValue"] = myString;
}

Anders Norås
http://dotnetjunkies.com/weblog/anoras/

 

[David Jessee]

Or, try this....

public class CrsInstnc : System.Web.UI.Page {
private const string vs_TcoRef = "TcoRef";

private void Page_Load(object sender, System.EventArgs e) {
if(!IsPostBack){
if(Request.QueryString["ref"] != null){
this.tcoRef = Request.QueryString["ref"].ToString();
}
...
}

protected string TcoRef{
get{
return
(this.ViewState[vs_TcoRef]==null)?string.Emptystring)this.ViewState[vs_Tco
Ref]);
}
set{
this.ViewState[vs_TcoRef]=value;
}
}