Building a dynamic LINQ query

Question

I have a listbox which users can select from a list if Towns, I want to be able to build a LINQ query based on the selected items in the list e.g.

Dim ddlTowns As ListBox = CType(Filter_Accommodation1.FindControl("ddlTowns"), ListBox)
        If Not ddlTowns Is Nothing Then
            For Each Item In ddlTowns.Items
                If Item.Selected Then
                    '// Build query
                End If
            Next
        End If

I have researched LinqKit as it appears to be able to do what I need but I cannot after hours of trying make any headway. I cannot find anything in VB which translates in anything meaningful or usable.

score 1 · Answer 1 · answered Mar 16 '11 at 00:50

Just had a Eureka moment and rather than using predicate I came up with this...

Private Function Filter_Accommomdation_QueryBuilder() As IEnumerable

            Dim ddlTowns As ListBox = CType(Filter_Accommodation1.FindControl("ddlTowns"), ListBox)
            Dim myList As New List(Of String)
            If Not ddlTowns Is Nothing Then
                For Each Item In ddlTowns.Items
                    If Item.Selected Then
                        myList.Add(Item.value)
                    End If
                Next
            End If

            Dim Filter_Query = _
                       From c In InitialQuery _
                       Where myList.ToArray.Contains(c.MyData.element("townvillage").value) _
                       Select c
            Return Filter_Query


        End Function

As a note I'm using c.MyData as the nature of InitialQuery demands a number of structured fields (the query is reused from various tables which by poor design aren't very consistant).

score 0 · Answer 2 · edited May 23 '17 at 12:11

0

Check out this question - contains some useful VB examples for you: Using PredicateBuilder with VB.NET

edited May 23 '17 at 12:11

Community

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answered Mar 16 '11 at 00:26

Stuart

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Building a dynamic LINQ query

2 Answers2