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Listbox containing duplicate items - correct selection not maintained on postback?

P: n/a
I have a page containing a list box. This list may contain duplicate
items - in which the ORDER is important.
ex:
a
b
b
a

is significant as compared to:
b
a
a
b

even though the list contains the same elements. The user has buttons on
the page to reorder the list.

The problem is that, say in the first example, the bottom 'a' is selected.
Then a button is pressed that causes a postback. The re-selected item is
now the FIRST a. Likewise, if the second 'b' is selected, on postback the
FIRST b will be selected.

The following page demonstrates this:

<%@ Page language="c#" Codebehind="WebForm1.aspx.cs" AutoEventWireup="false"
Inherits="testListbox.WebForm1" smartNavigation="True"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm1</title>
<meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
<meta name="CODE_LANGUAGE" Content="C#">
<meta name="vs_defaultClientScript" content="JavaScript">
<meta name="vs_targetSchema"
content="http://schemas.microsoft.com/intellisense/ie5">
</HEAD>
<body>
<form id="Form1" method="post" runat="server">
<asp:Button id="Button1" runat="server" Text="Button"></asp:Button>
<asp:ListBox id="ListBox1" runat="server">
<asp:ListItem Value="item1">item1</asp:ListItem>
<asp:ListItem Value="item2">item2</asp:ListItem>
<asp:ListItem Value="item1">item1</asp:ListItem>
</asp:ListBox>
</form>
</body>
</HTML>
There was no code added to the codebehind page. (I just created a simple
web app to demonstrate this).

Is there anyway to resolve this issue such that the correct element is
selected (by index rather than value)?
--
Adam Clauss

Nov 19 '05 #1
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10 Replies


P: n/a
Adam,

Yes the Listbox object has a SelectedIndex property, it gets or sets the
SelectedIndex.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
I have a page containing a list box. This list may contain duplicate
items - in which the ORDER is important.
ex:
a
b
b
a

is significant as compared to:
b
a
a
b

even though the list contains the same elements. The user has buttons on
the page to reorder the list.

The problem is that, say in the first example, the bottom 'a' is selected.
Then a button is pressed that causes a postback. The re-selected item is
now the FIRST a. Likewise, if the second 'b' is selected, on postback the
FIRST b will be selected.

The following page demonstrates this:

<%@ Page language="c#" Codebehind="WebForm1.aspx.cs"
AutoEventWireup="false" Inherits="testListbox.WebForm1"
smartNavigation="True"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm1</title>
<meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
<meta name="CODE_LANGUAGE" Content="C#">
<meta name="vs_defaultClientScript" content="JavaScript">
<meta name="vs_targetSchema"
content="http://schemas.microsoft.com/intellisense/ie5">
</HEAD>
<body>
<form id="Form1" method="post" runat="server">
<asp:Button id="Button1" runat="server" Text="Button"></asp:Button>
<asp:ListBox id="ListBox1" runat="server">
<asp:ListItem Value="item1">item1</asp:ListItem>
<asp:ListItem Value="item2">item2</asp:ListItem>
<asp:ListItem Value="item1">item1</asp:ListItem>
</asp:ListBox>
</form>
</body>
</HTML>
There was no code added to the codebehind page. (I just created a simple
web app to demonstrate this).

Is there anyway to resolve this issue such that the correct element is
selected (by index rather than value)?
--
Adam Clauss

Nov 19 '05 #2

P: n/a
Huh? Yes, I'm aware of that property.
The problem is I'm not setting the selection - ASP.NET is automatically.

--
Adam Clauss

"S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote in
message news:%2******************@tk2msftngp13.phx.gbl...
Adam,

Yes the Listbox object has a SelectedIndex property, it gets or sets the
SelectedIndex.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
I have a page containing a list box. This list may contain duplicate
items - in which the ORDER is important.
ex:
a
b
b
a

is significant as compared to:
b
a
a
b

even though the list contains the same elements. The user has buttons on
the page to reorder the list.

The problem is that, say in the first example, the bottom 'a' is
selected. Then a button is pressed that causes a postback. The
re-selected item is now the FIRST a. Likewise, if the second 'b' is
selected, on postback the FIRST b will be selected.

The following page demonstrates this:

<%@ Page language="c#" Codebehind="WebForm1.aspx.cs"
AutoEventWireup="false" Inherits="testListbox.WebForm1"
smartNavigation="True"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm1</title>
<meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
<meta name="CODE_LANGUAGE" Content="C#">
<meta name="vs_defaultClientScript" content="JavaScript">
<meta name="vs_targetSchema"
content="http://schemas.microsoft.com/intellisense/ie5">
</HEAD>
<body>
<form id="Form1" method="post" runat="server">
<asp:Button id="Button1" runat="server" Text="Button"></asp:Button>
<asp:ListBox id="ListBox1" runat="server">
<asp:ListItem Value="item1">item1</asp:ListItem>
<asp:ListItem Value="item2">item2</asp:ListItem>
<asp:ListItem Value="item1">item1</asp:ListItem>
</asp:ListBox>
</form>
</body>
</HTML>
There was no code added to the codebehind page. (I just created a simple
web app to demonstrate this).

Is there anyway to resolve this issue such that the correct element is
selected (by index rather than value)?
--
Adam Clauss


Nov 19 '05 #3

P: n/a
Yes,

You'll have to set it yourself.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
Huh? Yes, I'm aware of that property.
The problem is I'm not setting the selection - ASP.NET is automatically.

--
Adam Clauss

"S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote in
message news:%2******************@tk2msftngp13.phx.gbl...
Adam,

Yes the Listbox object has a SelectedIndex property, it gets or sets the
SelectedIndex.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
I have a page containing a list box. This list may contain duplicate
items - in which the ORDER is important.
ex:
a
b
b
a

is significant as compared to:
b
a
a
b

even though the list contains the same elements. The user has buttons
on the page to reorder the list.

The problem is that, say in the first example, the bottom 'a' is
selected. Then a button is pressed that causes a postback. The
re-selected item is now the FIRST a. Likewise, if the second 'b' is
selected, on postback the FIRST b will be selected.

The following page demonstrates this:

<%@ Page language="c#" Codebehind="WebForm1.aspx.cs"
AutoEventWireup="false" Inherits="testListbox.WebForm1"
smartNavigation="True"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm1</title>
<meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
<meta name="CODE_LANGUAGE" Content="C#">
<meta name="vs_defaultClientScript" content="JavaScript">
<meta name="vs_targetSchema"
content="http://schemas.microsoft.com/intellisense/ie5">
</HEAD>
<body>
<form id="Form1" method="post" runat="server">
<asp:Button id="Button1" runat="server" Text="Button"></asp:Button>
<asp:ListBox id="ListBox1" runat="server">
<asp:ListItem Value="item1">item1</asp:ListItem>
<asp:ListItem Value="item2">item2</asp:ListItem>
<asp:ListItem Value="item1">item1</asp:ListItem>
</asp:ListBox>
</form>
</body>
</HTML>
There was no code added to the codebehind page. (I just created a
simple web app to demonstrate this).

Is there anyway to resolve this issue such that the correct element is
selected (by index rather than value)?
--
Adam Clauss



Nov 19 '05 #4

P: n/a
In EVERY postback I do?? This page has a lot of postback's on it... that
doesn't seem very efficient.

--
Adam Clauss

"S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote in
message news:eD**************@TK2MSFTNGP09.phx.gbl...
Yes,

You'll have to set it yourself.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
Huh? Yes, I'm aware of that property.
The problem is I'm not setting the selection - ASP.NET is automatically.

--
Adam Clauss

"S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote in
message news:%2******************@tk2msftngp13.phx.gbl...
Adam,

Yes the Listbox object has a SelectedIndex property, it gets or sets the
SelectedIndex.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
I have a page containing a list box. This list may contain duplicate
items - in which the ORDER is important.
ex:
a
b
b
a

is significant as compared to:
b
a
a
b

even though the list contains the same elements. The user has buttons
on the page to reorder the list.

The problem is that, say in the first example, the bottom 'a' is
selected. Then a button is pressed that causes a postback. The
re-selected item is now the FIRST a. Likewise, if the second 'b' is
selected, on postback the FIRST b will be selected.

The following page demonstrates this:

<%@ Page language="c#" Codebehind="WebForm1.aspx.cs"
AutoEventWireup="false" Inherits="testListbox.WebForm1"
smartNavigation="True"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm1</title>
<meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
<meta name="CODE_LANGUAGE" Content="C#">
<meta name="vs_defaultClientScript" content="JavaScript">
<meta name="vs_targetSchema"
content="http://schemas.microsoft.com/intellisense/ie5">
</HEAD>
<body>
<form id="Form1" method="post" runat="server">
<asp:Button id="Button1" runat="server" Text="Button"></asp:Button>
<asp:ListBox id="ListBox1" runat="server">
<asp:ListItem Value="item1">item1</asp:ListItem>
<asp:ListItem Value="item2">item2</asp:ListItem>
<asp:ListItem Value="item1">item1</asp:ListItem>
</asp:ListBox>
</form>
</body>
</HTML>
There was no code added to the codebehind page. (I just created a
simple web app to demonstrate this).

Is there anyway to resolve this issue such that the correct element is
selected (by index rather than value)?
--
Adam Clauss




Nov 19 '05 #5

P: n/a
Adam,

Maybe I'm misunderstanding what you're doing. Does the item order in the
list box change with every post back. If the list box has viewstate enabled
on it it should stay exactly the same unless you re-bind it or the user
changes the order. Every time a post-back is done where the user changes the
order you'll have to set the proper index if .Net can't do it itself. But
that certainly shouldn't be on every post back.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
In EVERY postback I do?? This page has a lot of postback's on it... that
doesn't seem very efficient.

--
Adam Clauss

"S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote in
message news:eD**************@TK2MSFTNGP09.phx.gbl...
Yes,

You'll have to set it yourself.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
Huh? Yes, I'm aware of that property.
The problem is I'm not setting the selection - ASP.NET is automatically.

--
Adam Clauss

"S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote in
message news:%2******************@tk2msftngp13.phx.gbl...
Adam,

Yes the Listbox object has a SelectedIndex property, it gets or sets
the SelectedIndex.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
>I have a page containing a list box. This list may contain duplicate
>items - in which the ORDER is important.
> ex:
> a
> b
> b
> a
>
> is significant as compared to:
> b
> a
> a
> b
>
> even though the list contains the same elements. The user has buttons
> on the page to reorder the list.
>
> The problem is that, say in the first example, the bottom 'a' is
> selected. Then a button is pressed that causes a postback. The
> re-selected item is now the FIRST a. Likewise, if the second 'b' is
> selected, on postback the FIRST b will be selected.
>
> The following page demonstrates this:
>
> <%@ Page language="c#" Codebehind="WebForm1.aspx.cs"
> AutoEventWireup="false" Inherits="testListbox.WebForm1"
> smartNavigation="True"%>
> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
> <HTML>
> <HEAD>
> <title>WebForm1</title>
> <meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
> <meta name="CODE_LANGUAGE" Content="C#">
> <meta name="vs_defaultClientScript" content="JavaScript">
> <meta name="vs_targetSchema"
> content="http://schemas.microsoft.com/intellisense/ie5">
> </HEAD>
> <body>
> <form id="Form1" method="post" runat="server">
> <asp:Button id="Button1" runat="server" Text="Button"></asp:Button>
> <asp:ListBox id="ListBox1" runat="server">
> <asp:ListItem Value="item1">item1</asp:ListItem>
> <asp:ListItem Value="item2">item2</asp:ListItem>
> <asp:ListItem Value="item1">item1</asp:ListItem>
> </asp:ListBox>
> </form>
> </body>
> </HTML>
>
>
> There was no code added to the codebehind page. (I just created a
> simple web app to demonstrate this).
>
> Is there anyway to resolve this issue such that the correct element is
> selected (by index rather than value)?
> --
> Adam Clauss
>
>
>



Nov 19 '05 #6

P: n/a
Again - try running the code/page I gave on the first post.
I do not have to change or reorder anything to cause this problem.

Problem in short - have a page with a button (with no event actually bound
to it), and a listbox with contents as:
a
b
b
a

Select the bottom a. Then press the button.
The first a is what shows up as selected when the page reappears.

Select the bottom b. Then press the button.
The first b is what shows up as selected when the page reappears.

--
Adam Clauss

"S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote in
message news:u1**************@TK2MSFTNGP09.phx.gbl...
Adam,

Maybe I'm misunderstanding what you're doing. Does the item order in the
list box change with every post back. If the list box has viewstate
enabled on it it should stay exactly the same unless you re-bind it or the
user changes the order. Every time a post-back is done where the user
changes the order you'll have to set the proper index if .Net can't do it
itself. But that certainly shouldn't be on every post back.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
In EVERY postback I do?? This page has a lot of postback's on it... that
doesn't seem very efficient.

--
Adam Clauss

"S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote in
message news:eD**************@TK2MSFTNGP09.phx.gbl...
Yes,

You'll have to set it yourself.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
Huh? Yes, I'm aware of that property.
The problem is I'm not setting the selection - ASP.NET is
automatically.

--
Adam Clauss

"S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote in
message news:%2******************@tk2msftngp13.phx.gbl...
> Adam,
>
> Yes the Listbox object has a SelectedIndex property, it gets or sets
> the SelectedIndex.
>
> --
> Sincerely,
>
> S. Justin Gengo, MCP
> Web Developer / Programmer
>
> www.aboutfortunate.com
>
> "Out of chaos comes order."
> Nietzsche
> "Adam Clauss" <ca*****@tamu.edu> wrote in message
> news:11*************@corp.supernews.com...
>>I have a page containing a list box. This list may contain duplicate
>>items - in which the ORDER is important.
>> ex:
>> a
>> b
>> b
>> a
>>
>> is significant as compared to:
>> b
>> a
>> a
>> b
>>
>> even though the list contains the same elements. The user has
>> buttons on the page to reorder the list.
>>
>> The problem is that, say in the first example, the bottom 'a' is
>> selected. Then a button is pressed that causes a postback. The
>> re-selected item is now the FIRST a. Likewise, if the second 'b' is
>> selected, on postback the FIRST b will be selected.
>>
>> The following page demonstrates this:
>>
>> <%@ Page language="c#" Codebehind="WebForm1.aspx.cs"
>> AutoEventWireup="false" Inherits="testListbox.WebForm1"
>> smartNavigation="True"%>
>> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
>> <HTML>
>> <HEAD>
>> <title>WebForm1</title>
>> <meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
>> <meta name="CODE_LANGUAGE" Content="C#">
>> <meta name="vs_defaultClientScript" content="JavaScript">
>> <meta name="vs_targetSchema"
>> content="http://schemas.microsoft.com/intellisense/ie5">
>> </HEAD>
>> <body>
>> <form id="Form1" method="post" runat="server">
>> <asp:Button id="Button1" runat="server" Text="Button"></asp:Button>
>> <asp:ListBox id="ListBox1" runat="server">
>> <asp:ListItem Value="item1">item1</asp:ListItem>
>> <asp:ListItem Value="item2">item2</asp:ListItem>
>> <asp:ListItem Value="item1">item1</asp:ListItem>
>> </asp:ListBox>
>> </form>
>> </body>
>> </HTML>
>>
>>
>> There was no code added to the codebehind page. (I just created a
>> simple web app to demonstrate this).
>>
>> Is there anyway to resolve this issue such that the correct element
>> is selected (by index rather than value)?
>> --
>> Adam Clauss
>>
>>
>>
>
>



Nov 19 '05 #7

P: n/a
Adam Clauss wrote:
I have a page containing a list box. This list may contain duplicate
items - in which the ORDER is important.
ex:
a
b
b
a

is significant as compared to:
b
a
a
b

even though the list contains the same elements. The user has buttons on
the page to reorder the list.

The problem is that, say in the first example, the bottom 'a' is selected.
Then a button is pressed that causes a postback. The re-selected item is
now the FIRST a. Likewise, if the second 'b' is selected, on postback the
FIRST b will be selected.

The following page demonstrates this:

<%@ Page language="c#" Codebehind="WebForm1.aspx.cs" AutoEventWireup="false"
Inherits="testListbox.WebForm1" smartNavigation="True"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm1</title>
<meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
<meta name="CODE_LANGUAGE" Content="C#">
<meta name="vs_defaultClientScript" content="JavaScript">
<meta name="vs_targetSchema"
content="http://schemas.microsoft.com/intellisense/ie5">
</HEAD>
<body>
<form id="Form1" method="post" runat="server">
<asp:Button id="Button1" runat="server" Text="Button"></asp:Button>
<asp:ListBox id="ListBox1" runat="server">
<asp:ListItem Value="item1">item1</asp:ListItem>
<asp:ListItem Value="item2">item2</asp:ListItem>
<asp:ListItem Value="item1">item1</asp:ListItem>
</asp:ListBox>
</form>
</body>
</HTML>

The listbox needs to have distinct item values in order to distinguish
the items within it.

Try, for instance:

<asp:ListItem Value="item1_instance1">item1</asp:ListItem>
<asp:ListItem Value="item2_instance1">item2</asp:ListItem>
<asp:ListItem Value="item1_instance2">item1</asp:ListItem>

Or anything else. If you're only concerned with the textual contents of
the listbox for everything else, the values could simply be 1, 2, 3,
....

Damien

Nov 19 '05 #8

P: n/a
Ah... that did it. Yeah - only the text is significant, so I was able to
disregard the actual values (just plugged in an incrementing value).

--
Adam Clauss

"Damien" <Da*******************@hotmail.com> wrote in message
news:11**********************@g43g2000cwa.googlegr oups.com...
Adam Clauss wrote:
I have a page containing a list box. This list may contain duplicate
items - in which the ORDER is important.
ex:
a
b
b
a

is significant as compared to:
b
a
a
b

even though the list contains the same elements. The user has buttons on
the page to reorder the list.

The problem is that, say in the first example, the bottom 'a' is
selected.
Then a button is pressed that causes a postback. The re-selected item is
now the FIRST a. Likewise, if the second 'b' is selected, on postback
the
FIRST b will be selected.

The following page demonstrates this:

<%@ Page language="c#" Codebehind="WebForm1.aspx.cs"
AutoEventWireup="false"
Inherits="testListbox.WebForm1" smartNavigation="True"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm1</title>
<meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
<meta name="CODE_LANGUAGE" Content="C#">
<meta name="vs_defaultClientScript" content="JavaScript">
<meta name="vs_targetSchema"
content="http://schemas.microsoft.com/intellisense/ie5">
</HEAD>
<body>
<form id="Form1" method="post" runat="server">
<asp:Button id="Button1" runat="server" Text="Button"></asp:Button>
<asp:ListBox id="ListBox1" runat="server">
<asp:ListItem Value="item1">item1</asp:ListItem>
<asp:ListItem Value="item2">item2</asp:ListItem>
<asp:ListItem Value="item1">item1</asp:ListItem>
</asp:ListBox>
</form>
</body>
</HTML>

The listbox needs to have distinct item values in order to distinguish
the items within it.

Try, for instance:

<asp:ListItem Value="item1_instance1">item1</asp:ListItem>
<asp:ListItem Value="item2_instance1">item2</asp:ListItem>
<asp:ListItem Value="item1_instance2">item1</asp:ListItem>

Or anything else. If you're only concerned with the textual contents of
the listbox for everything else, the values could simply be 1, 2, 3,
...

Damien

Nov 19 '05 #9

P: n/a
OK - maybe partially my fault for giving a bad example in my first post.
Damien hit the problem.

What the first example should have said was that:
a
b
b
a **selected

is significant as to:
a **selected
b
b
a

Order itself is important too, but that wasn't the actual problem.
Apologies for being unclear and making things confusing :)

--
Adam Clauss

"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
Again - try running the code/page I gave on the first post.
I do not have to change or reorder anything to cause this problem.

Problem in short - have a page with a button (with no event actually bound
to it), and a listbox with contents as:
a
b
b
a

Select the bottom a. Then press the button.
The first a is what shows up as selected when the page reappears.

Select the bottom b. Then press the button.
The first b is what shows up as selected when the page reappears.

--
Adam Clauss

"S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote in
message news:u1**************@TK2MSFTNGP09.phx.gbl...
Adam,

Maybe I'm misunderstanding what you're doing. Does the item order in the
list box change with every post back. If the list box has viewstate
enabled on it it should stay exactly the same unless you re-bind it or
the user changes the order. Every time a post-back is done where the user
changes the order you'll have to set the proper index if .Net can't do it
itself. But that certainly shouldn't be on every post back.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
In EVERY postback I do?? This page has a lot of postback's on it...
that doesn't seem very efficient.

--
Adam Clauss

"S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote in
message news:eD**************@TK2MSFTNGP09.phx.gbl...
Yes,

You'll have to set it yourself.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
> Huh? Yes, I'm aware of that property.
> The problem is I'm not setting the selection - ASP.NET is
> automatically.
>
> --
> Adam Clauss
>
> "S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote
> in message news:%2******************@tk2msftngp13.phx.gbl...
>> Adam,
>>
>> Yes the Listbox object has a SelectedIndex property, it gets or sets
>> the SelectedIndex.
>>
>> --
>> Sincerely,
>>
>> S. Justin Gengo, MCP
>> Web Developer / Programmer
>>
>> www.aboutfortunate.com
>>
>> "Out of chaos comes order."
>> Nietzsche
>> "Adam Clauss" <ca*****@tamu.edu> wrote in message
>> news:11*************@corp.supernews.com...
>>>I have a page containing a list box. This list may contain duplicate
>>>items - in which the ORDER is important.
>>> ex:
>>> a
>>> b
>>> b
>>> a
>>>
>>> is significant as compared to:
>>> b
>>> a
>>> a
>>> b
>>>
>>> even though the list contains the same elements. The user has
>>> buttons on the page to reorder the list.
>>>
>>> The problem is that, say in the first example, the bottom 'a' is
>>> selected. Then a button is pressed that causes a postback. The
>>> re-selected item is now the FIRST a. Likewise, if the second 'b' is
>>> selected, on postback the FIRST b will be selected.
>>>
>>> The following page demonstrates this:
>>>
>>> <%@ Page language="c#" Codebehind="WebForm1.aspx.cs"
>>> AutoEventWireup="false" Inherits="testListbox.WebForm1"
>>> smartNavigation="True"%>
>>> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
>>> <HTML>
>>> <HEAD>
>>> <title>WebForm1</title>
>>> <meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
>>> <meta name="CODE_LANGUAGE" Content="C#">
>>> <meta name="vs_defaultClientScript" content="JavaScript">
>>> <meta name="vs_targetSchema"
>>> content="http://schemas.microsoft.com/intellisense/ie5">
>>> </HEAD>
>>> <body>
>>> <form id="Form1" method="post" runat="server">
>>> <asp:Button id="Button1" runat="server"
>>> Text="Button"></asp:Button>
>>> <asp:ListBox id="ListBox1" runat="server">
>>> <asp:ListItem Value="item1">item1</asp:ListItem>
>>> <asp:ListItem Value="item2">item2</asp:ListItem>
>>> <asp:ListItem Value="item1">item1</asp:ListItem>
>>> </asp:ListBox>
>>> </form>
>>> </body>
>>> </HTML>
>>>
>>>
>>> There was no code added to the codebehind page. (I just created a
>>> simple web app to demonstrate this).
>>>
>>> Is there anyway to resolve this issue such that the correct element
>>> is selected (by index rather than value)?
>>> --
>>> Adam Clauss
>>>
>>>
>>>
>>
>>
>
>



Nov 19 '05 #10

P: n/a
Adam,

Ok, now I understand. What's happening is that when you post back .NET is
setting the list box based on the value selected.

Think about how you would write the code to find which item was selected...

1) You receive a form value sent in a post
2) You know the post came from a certain list box
3) You need to make certain the same value is selected when the web page is
returned to the client.
4) The list box has a method: SelectedItem which takes a string.
5) Assume that SelectedItem iterates through each value in the list box
until it finds the one that matches the string posted.

Well, because you have the same exact text and values in your list box the
first one found in the iteration matches and the loop is exited.

How to correct this? Make certain that your list box has different values.

For example, if you were adding these values to the list box by hand you
could do this:
ListBox1.Items.Add(New ListItem("a", "1"))
ListBox1.Items.Add(New ListItem("b", "2"))
ListBox1.Items.Add(New ListItem("b", "3"))
ListBox1.Items.Add(New ListItem("a", "4"))

If you use the code above you'll see that picking the bottom "a" and then
posting back will keep the bottom "a" selected because we've given the code
a way to discriminate between items.
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
OK - maybe partially my fault for giving a bad example in my first post.
Damien hit the problem.

What the first example should have said was that:
a
b
b
a **selected

is significant as to:
a **selected
b
b
a

Order itself is important too, but that wasn't the actual problem.
Apologies for being unclear and making things confusing :)

--
Adam Clauss

"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
Again - try running the code/page I gave on the first post.
I do not have to change or reorder anything to cause this problem.

Problem in short - have a page with a button (with no event actually
bound to it), and a listbox with contents as:
a
b
b
a

Select the bottom a. Then press the button.
The first a is what shows up as selected when the page reappears.

Select the bottom b. Then press the button.
The first b is what shows up as selected when the page reappears.

--
Adam Clauss

"S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote in
message news:u1**************@TK2MSFTNGP09.phx.gbl...
Adam,

Maybe I'm misunderstanding what you're doing. Does the item order in the
list box change with every post back. If the list box has viewstate
enabled on it it should stay exactly the same unless you re-bind it or
the user changes the order. Every time a post-back is done where the
user changes the order you'll have to set the proper index if .Net can't
do it itself. But that certainly shouldn't be on every post back.

--
Sincerely,

S. Justin Gengo, MCP
Web Developer / Programmer

www.aboutfortunate.com

"Out of chaos comes order."
Nietzsche
"Adam Clauss" <ca*****@tamu.edu> wrote in message
news:11*************@corp.supernews.com...
In EVERY postback I do?? This page has a lot of postback's on it...
that doesn't seem very efficient.

--
Adam Clauss

"S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote in
message news:eD**************@TK2MSFTNGP09.phx.gbl...
> Yes,
>
> You'll have to set it yourself.
>
> --
> Sincerely,
>
> S. Justin Gengo, MCP
> Web Developer / Programmer
>
> www.aboutfortunate.com
>
> "Out of chaos comes order."
> Nietzsche
> "Adam Clauss" <ca*****@tamu.edu> wrote in message
> news:11*************@corp.supernews.com...
>> Huh? Yes, I'm aware of that property.
>> The problem is I'm not setting the selection - ASP.NET is
>> automatically.
>>
>> --
>> Adam Clauss
>>
>> "S. Justin Gengo" <sjgengo@[no_spam_please]aboutfortunate.com> wrote
>> in message news:%2******************@tk2msftngp13.phx.gbl...
>>> Adam,
>>>
>>> Yes the Listbox object has a SelectedIndex property, it gets or sets
>>> the SelectedIndex.
>>>
>>> --
>>> Sincerely,
>>>
>>> S. Justin Gengo, MCP
>>> Web Developer / Programmer
>>>
>>> www.aboutfortunate.com
>>>
>>> "Out of chaos comes order."
>>> Nietzsche
>>> "Adam Clauss" <ca*****@tamu.edu> wrote in message
>>> news:11*************@corp.supernews.com...
>>>>I have a page containing a list box. This list may contain
>>>>duplicate items - in which the ORDER is important.
>>>> ex:
>>>> a
>>>> b
>>>> b
>>>> a
>>>>
>>>> is significant as compared to:
>>>> b
>>>> a
>>>> a
>>>> b
>>>>
>>>> even though the list contains the same elements. The user has
>>>> buttons on the page to reorder the list.
>>>>
>>>> The problem is that, say in the first example, the bottom 'a' is
>>>> selected. Then a button is pressed that causes a postback. The
>>>> re-selected item is now the FIRST a. Likewise, if the second 'b'
>>>> is selected, on postback the FIRST b will be selected.
>>>>
>>>> The following page demonstrates this:
>>>>
>>>> <%@ Page language="c#" Codebehind="WebForm1.aspx.cs"
>>>> AutoEventWireup="false" Inherits="testListbox.WebForm1"
>>>> smartNavigation="True"%>
>>>> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
>>>> <HTML>
>>>> <HEAD>
>>>> <title>WebForm1</title>
>>>> <meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
>>>> <meta name="CODE_LANGUAGE" Content="C#">
>>>> <meta name="vs_defaultClientScript" content="JavaScript">
>>>> <meta name="vs_targetSchema"
>>>> content="http://schemas.microsoft.com/intellisense/ie5">
>>>> </HEAD>
>>>> <body>
>>>> <form id="Form1" method="post" runat="server">
>>>> <asp:Button id="Button1" runat="server"
>>>> Text="Button"></asp:Button>
>>>> <asp:ListBox id="ListBox1" runat="server">
>>>> <asp:ListItem Value="item1">item1</asp:ListItem>
>>>> <asp:ListItem Value="item2">item2</asp:ListItem>
>>>> <asp:ListItem Value="item1">item1</asp:ListItem>
>>>> </asp:ListBox>
>>>> </form>
>>>> </body>
>>>> </HTML>
>>>>
>>>>
>>>> There was no code added to the codebehind page. (I just created a
>>>> simple web app to demonstrate this).
>>>>
>>>> Is there anyway to resolve this issue such that the correct element
>>>> is selected (by index rather than value)?
>>>> --
>>>> Adam Clauss
>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>
>



Nov 19 '05 #11

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