Listbox control not preserving selected item on button click.

[MonkOFox]

Ok so I have two listboxes on my page one for users and another for cases. For some reason the users listbox preserves state, but the cases listbox doesn't.

They're both set EnableViewState= true

                <asp:ListBox ID="ExistingUsers" runat="server" Width="45%" Height="189px" 
                    CssClass="createdusers" ></asp:ListBox>
                <asp:ListBox ID="ExistingCases" runat="server" Width="45%" Height="190px" 
                    ></asp:ListBox>

I tried setting them both to autopostback, but that didn't help. The users listbox would preserve the selected item, but make it the first viewable item in the list. The cases listbox still reset the selected item to the first.

My page load:

'....

        If Not Page.IsPostBack Then
            ''Sort later.
            Dim i As Integer = 10
            For Each usr As String In AttRoleProvider.GetUsersInRole("Role1")
                Me.ExistingUsers.Items.Add(usr)
            Next
        End If

        If Not Page.IsPostBack Then
            Dim ds As DataSet = dbops.ExecuteSQLServerSelectCommand(SQL, Nothing)
            If ds IsNot Nothing Then
                Dim dt As DataTable = ds.Tables(0)
                Me.ExistingCases.DataSource = dt
                Me.ExistingCases.DataTextField = "Text"
                Me.ExistingCases.DataValueField = "Value"
                Try
                    Me.ExistingCases.DataBind()
                Catch ex As Exception
                    Throw ex
                End Try
            End If
        End If

'....

[MonkOFox]

Hmmm so it seems that if you bind the DataTextField and the DataValueField that the control will not maintain the selected state. That value does make it easier than have to query again based on the selected text. Is there a way to get this to work with value-binding?

[KGComputers]

Hi,

I tested your .aspx markup and created some dummy .cs methods which add items through item collection for users
and List object with class (with properties Id and Name) as it's type somewhat similar to a data table object.

I only used one condition to test the if the page state is IsPostBack. I noticed in your code in which your using separate conditions for testing IsPostBack.

Page load condition using explicit setting and not from a database result.

If Not Page.IsPostBack Then


    For i As Integer = 0 To 3
        users.Add("user" & i)
        Me.ExistingUsers.Items.Add("user" & i)
        roles.Add(New Roles() With { _
            Key .ID = i, _
            Key .Name = "Role" & i _
        })
    Next


    Me.ExistingCases.DataSource = roles
    Me.ExistingCases.DataTextField = "Name"
    Me.ExistingCases.DataValueField = "Id"
    Me.ExistingCases.DataBind()


    Session("users") = users
    Session("roles") = roles
End If

button event:

Protected Sub btnShowSelected_Click(sender As Object, e As EventArgs)
    If Me.ExistingCases.SelectedItem IsNot Nothing AndAlso Me.ExistingUsers.SelectedItem IsNot Nothing Then
        Response.Write("User: " & Me.ExistingUsers.SelectedItem.ToString() & ", Role: " & Me.ExistingCases.SelectedItem.ToString())
    End If
End Sub

aspx markup

<div>
        <div class="container">
            <div id="Users">
                 <asp:ListBox ID="ExistingUsers" runat="server" EnableViewState="true" Width="150px" Height="189px" ></asp:ListBox>
            </div>
            <div id="Cases">
                <asp:ListBox ID="ExistingCases" runat="server"  EnableViewState="true"  Width="150px" Height="190px"></asp:ListBox>
            </div>
             <div id="footer">
                <asp:Button ID="btnShowSelected" runat="server" Text="Submit" 
                     onclick="btnShowSelected_Click" />
            </div>
        </div>       
    </div>

The state of the two listbox controls are preserved even on postbacks. Try checking your markup as well. Are you using ajax/update panels or plain server side asp.net?

Possible issue is that you set autopostback property of the listbox control.

[MonkOFox]

I"ll test the cases listbox with a custom class with the same property names as the db fields I'm binding to. I'll see if that has a different outcome than binding a datatable.

I'm positive I have the autopostback equal to false on both controls in the properties panel. I'm not using any ajax for this web app.

Thank you for the response.

[KGComputers]

I believe using a List<YourType> or datatable has nothing to do with the issue. It can be the aspx markup or some logic behind your app.