ASP .NET using C# problem !!

wireblock · July 9th, 2003, 02:51 AM

Hi,

I got the following code:

<script runat="server" language="c#">
void Page_Load()
{
if (Request.Form["list1"] != "")
{
message.Text = "You have selected " + Request.Form["list1"];
}
}
</script>
<html>
<head>
<title>Drop Down List Example</title>
</head>
<body>
<asp:label id="message" runat="server"/>
<br />
<form runat="server">
Which city do you wish to look at hotels for?<br /><br />
<asp:listbox id="list1" runat="server" selectionmode="multiple">
<asp:listitem>Madrid</asp:listitem>
<asp:listitem>Oslo</asp:listitem>
<asp:listitem>Lisbon</asp:listitem>
</asp:listbox>
<br /><br /><br /><br />
<input type="Submit">
</form>
</body>
</html>

When the 1st time I ran this page in IE 6.0 by entering 127.0.0.1/ch01/listpage.aspx

The message label shouldn't come out with the phrase "You have selected " since I have prevented it from appearing using the asp script with the if statement. But it still display when I 1st load the page.
Pls...................help......................!!

NotNowJohn · July 9th, 2003, 09:15 AM

If you want to prevent the label's text from appearing you can use IsPostBack page's property. That means that the code piece will be run only if the form has submitted.

Code:

void Page_Load()
{
    if (IsPostBack)
    {
        if (Request.Form["list1"] != "") 
        {
            message.Text = "You have selected " + Request.Form["list1"];
        }
    }
}

Regs,
NNJ

...but the Soon is eclipsed by the Moon

wireblock · July 9th, 2003, 10:40 AM

Thanks a lot NotNowJohn ! It's working now !

wireblock · July 9th, 2003, 09:54 PM

Hi,

  If I changed the asp script to below:

  void Page_Load()
  {
if (IsPostBack)
{
     if (Request.Form["list1"] != "")
        message.Text = "You have selected " + Request.Form["list1"];
     else
        message.Text = "You have selected nothing";
    }
  }

  and select nothing from the listbox, the label(message) should display "You have selected nothing". Why is that it still display "You have selected " ??

R there a lot of bugs inside Wrox book?

Quote:

quote:Originally posted by NotNowJohn
If you want to prevent the label's text from appearing you can use IsPostBack page's property. That means that the code piece will be run only if the form has submitted.

Code:

void Page_Load()
{
    if (IsPostBack)
    {
        if (Request.Form["list1"] != "") 
        {
            message.Text = "You have selected " + Request.Form["list1"];
        }
    }
}

Regs,
NNJ

...but the Soon is eclipsed by the Moon

NotNowJohn · July 10th, 2003, 10:38 AM

You don't have to use Request.Form collection in order to restore the value of listbox. In ASPX pages u can use the variable list1 instead of Request.Form["list1"];
For the appropriate message u can use following code:

Code:

 if (list1.SelectedIndex!=-1) 
        message.Text = "You have selected " + list1.SelectedItem.Text;
     else
        message.Text = "You have selected nothing";

...but the Soon is eclipsed by the Moon

wireblock · July 11th, 2003, 09:33 AM

Thks a lot John !