page not picking up listbox items

**flynny1st** · April 23rd, 2008, 06:28 AM

Hi all,

hopefully this is easy.

I have two listboxes on my pages, one of which is populated with a list of types from a database. The second listbox next to it contains will contain all those associated with the product i am entering.

using javascript i move the items between the tables. this is all working.

now when i click the add button (this will iterate through the added types in the second list box and add the associations to the database). it is saying the number of items in the list is 0? can anyone explain why please?

i though it may be something to do with the postback but his is protected.

Code:

<%@ Page Language="vb" AutoEventWireup="true" CodeFile="add_product.aspx.vb" Theme="Admin" Inherits="add_product" debug="true"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
	<head id="Head1" runat="server">
		<title>Add a New Product</title>
...
				<tr>
					<td>
						<asp:listbox CssClass="stdListBox" id="availableTypes" runat="server"/>
						<asp:listbox CssClass="stdListBox" id="productTypes" runat="server"/>
					</td>
				</tr>
...
				<tr>
					<td align="center" colspan=2><asp:button id="nextPage" text="Next >>" OnCommand="AddProductClick" runat="server"/> </td>
				</tr>

Code:

    Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)

	'*************** AUTH STUFF *************************************
	Dim MM_authFailedURL As String = "..\admin_access_denied.aspx"
	Dim MM_grantAccess As Boolean = false

	If Session("MM_Username") <> "" Then
   		MM_grantAccess = true
	End If
	
	If Not MM_grantAccess Then
		Response.Redirect(MM_authFailedURL)
	End If
	'*****************************************************************

	If Not Page.IsPostBack Then

	Dim dt As DataTable
	
	oQry = "SELECT supplierID, name FROM suppliers ORDER BY name"
        SupplierDropDown.DataSource = CreateDataSource(oQry)
	SupplierDropDown.DataTextField = "name"
	SupplierDropDown.DataValueField = "supplierID"
        SupplierDropDown.DataBind()

	'initialize the image datagrid
	dt = new DataTable("ProductImages")
	dt.Columns.Add(new DataColumn("imageID", GetType(Integer)))
	dt.Columns.Add(new DataColumn("image", GetType(String)))
	dt.NewRow()

	If Not (Request.QueryString("ID")Is Nothing) Then
		
		productID = Request.QueryString("ID")
		
		'set supplier
		SupplierDropDown.SelectedItem.Value = productID

		'now do lookup for rest of information
		oQry = "SELECT * FROM products WHERE productID=" + productID
		Dim pDataSet As DataSet = CreateDataSource(oQry)

		productName.Text = pDataSet.Tables(0).Rows(0).Item("name")
		briefDescription.Text = pDataSet.Tables(0).Rows(0).Item("brief_des")
		detailedDescription.Text = pDataSet.Tables(0).Rows(0).Item("full_des")
		labelInfo.Text = pDataSet.Tables(0).Rows(0).Item("label")
		directions.Text = pDataSet.Tables(0).Rows(0).Item("directions")

		'now select all sizes not associated
		oQry = "SELECT * FROM sizes WHERE sizeID NOT IN (SELECT sizeID from productSize WHERE productID=" + productID + ") ORDER BY sizes.size"
		pDataSet = CreateDataSource(oQry)
		availableSizes.DataSource = pDataSet
		availableSizes.DataTextField = "size"
		availableSizes.DataValueField = "sizeID"
	        availableSizes.DataBind()

		'and select all those which are associated
		oQry = "SELECT * FROM sizes,productSize WHERE sizes.sizeID = productSize.sizeID AND productSize.productID=" + productID + " ORDER BY size"
		pDataSet = CreateDataSource(oQry)
		productSizes.DataSource = pDataSet
		productSizes.DataTextField = "size"
		productSizes.DataValueField = "sizeID"
	        productSizes.DataBind()

		'do the same for all the types
		oQry = "SELECT * FROM types WHERE typeID NOT IN (SELECT typeID from productType WHERE productID=" & productID & ") ORDER BY types.type"
		pDataSet = CreateDataSource(oQry)
		availableTypes.DataSource = pDataSet
		availableTypes.DataTextField = "type"
		availableTypes.DataValueField = "typeID"
	        availableTypes.DataBind()

		oQry = "SELECT * FROM types,productType WHERE types.typeID = productType.typeID AND productType.productID=" & productID & " ORDER BY type"
		pDataSet = CreateDataSource(oQry)
		productTypes.DataSource = pDataSet
		productTypes.DataTextField = "type"
		productTypes.DataValueField = "typeID"
	        productTypes.DataBind()

		'now check for images
		oQry = "SELECT * FROM ((images INNER JOIN productImages ON images.imageID = productImages.imageID) INNER JOIN products ON products.productID = productImages.productID) WHERE products.productID=" + productID
		'response.write(oQry)
		pDataSet = CreateDataSource(oQry)

		Dim i As Integer = 0 
		For i = 0 To pDataSet.Tables(0).Rows.Count-1
			Dim newImageRow As DataRow = dt.NewRow()

			newImageRow("imageID") = pDataSet.Tables(0).Rows(i).Item("imageID")
			newImageRow("image") = pDataSet.Tables(0).rows(i).Item("location")
		Next		
	Else
		'select all sizes
		oQry = "SELECT * FROM sizes ORDER BY size"
		Dim pDataSet As DataSet = CreateDataSource(oQry)
		availableSizes.DataSource = pDataSet
		availableSizes.DataTextField = "size"
		availableSizes.DataValueField = "sizeID"
	        availableSizes.DataBind()

		'select all types
		oQry = "SELECT * FROM types ORDER BY type"
		pDataSet = CreateDataSource(oQry)
		availableTypes.DataSource = pDataSet
		availableTypes.DataTextField = "type"
		availableTypes.DataValueField = "typeID"
	        availableTypes.DataBind()
	End If	

	'now databind datagrid
	imageDatagrid.DataSource = dt
	imageDatagrid.DataBind()

	Session("imagesDataTable")=dt

	End If
	
	Response.Write("always getting to here?? <br>")

    End Sub

**MikeVallotton** · April 23rd, 2008, 02:29 PM

I didn't read your code, but it probably has to do with viewstate. Javascript doesn't add the items to the viewstate, so when you post back, the control still thinks it's empty.

There's probably a better way to get around it, but what I've done in the past is build a comma delimited string in a hidden textbox (using javascript) before I postback, then split it in the server-side code.

**flynny1st** · April 24th, 2008, 03:31 AM

Hi Mike,

thanks for the reply, i see.

so what you are saying is i would have a hidden label and on the onclick javascript add method append to the string and on the remove remove from the string?

would this not have the same problem as before with it not being seeing the labels string?

(sorry a newb as you can tell!)

**MikeVallotton** · April 24th, 2008, 11:48 AM

Make it a hidden textbox, not a label. This is not an asp:TextBox Visible=false - this is an asp:TextBox with a style="visibility:hidden;".

Textboxes and Listboxes deal with viewstate differently, so you will get the value of the textbox on postback.

I'd build the comma delimited list in the javascript onSubmit handler, rather than adding and removing and dealing with the complication that entails.

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