Linq Condition help - vb.net

Question

I have a list box where users can select multiple items. Options available in the list box are added below. 
1st option is select all and is selected by Default.

if selectall is selected I need to make the linq query not to validate for any condition. (should display all)

if not I need to filter for the values selected how can I do that??



options
================
selectall
Level1 Products
Level2products
Level3Products



Dim Query = (from p in Dc.Products Join  O on Dc.Orders On p.ProductId equals O.ProductId
where o.Status = "Delivered"  
/***Here I need Add the listbox filter condition smething like ddlitem.selectedValues.contains(p.level)***/
Select
ProductId = p.ProductId.Tostring(), _
OrderStatus = O.OrderStatus.tostring(),_
OrderNumber = O.OrderNumber(),_
ProductLevel = p.Level())
How can I do that?? I am a newbie in linq.
Thank you,
Lily

Answer 1

Hi Lily,

If you are using WinForms ListBox control, there is SelectedItems property to indicate the selected items. If p.level has the some text with items in ListBox, you can add the filter condition in where statement, like:

Dim Query = From ... In ... 
            Where o.Status = "Delivered" AndAlso ListBox1.SelectedItems.Contains(p.Level)
            Select ...

If the text in p.Level is not the same with the text in ListBox's items, you would probably use Where() method and pass a Func<> delegate. Return True when the item is needed after filtering.  ListBox's SelectedIndices property can be used to determine which item is selected.

Best regards,

---

Chester Hong
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Answer 2

 got it resolved. I am adding all the items to a list (ListAll) and doing Listselected where I am adding  Only selected items from the dropdown

if ddlitem.selectedIndex = 0, listall.contains(p.level), listselected.contains(p.level)