Where clause on dynamic column name in LINQ query? - sql

Question

I've created a dropdown with some column names in a table in my db. When a user selects a column name i want to add a where clause to the query to use this filter.
What i'm trying to do is:
Dim objQuery = (From wc In _dbBellen.dealer_telefonies Order By wc.Bedrijfsnaam Select wc)
'if dropdown has value...
objQuery = objQuery.Where(Function(wc) wc.DynamicColumnName < txtFilterValue1.Text)
The wc.DynamicColumnName has to be replaced by for example wc.Price.
--
The code what i'm tried now after some replies is:
Dim objQuery = (From wc In _dbBellen.dealer_telefonies Order By wc.Bedrijfsnaam Select wc)
If ddlFilterColumn1.SelectedValue <> "" And ddlFilterOperator1.SelectedValue <> "" And txtFilterValue1.Text <> "" Then
Select Case ddlFilterOperator1.SelectedValue
Case "..%"
objQuery = objQuery.Where(Function(wc) wc.WHMCSClient_id Like txtFilterValue1.Text & "%")
Case "%.."
objQuery = objQuery.Where(Function(wc) wc.WHMCSClient_id Like "%" & txtFilterValue1.Text)
Case Else '< > = <>
'objQuery = objQuery.Where(Function(wc) wc.WHMCSClient_id < txtFilterValue1.Text)
'objQuery = objQuery.Where(Function(wc) "wc." + ddlFilterColumn1.SelectedValue.ToString + " < " + txtFilterValue1.Text)
objQuery = objQuery.Where(Function(wc) "wc.WHMCSClient_id < 500")
End Select
End If
Response.Write(objQuery.ToString())
But i am getting the following error (original error is in dutch but it said as follow):
The conversion from string wc.WHMCSClient_id < 500 to type Boolean is invalid.

Answer 1

This is quite an old article, but I think it's still viable
Scott Gu posted about the Dynamic LINQ library a while back which essentially allows you to use strings to query collections in a "LINQ"-type format., i.e. something like this:
Dim objQuery = (From wc In _dbBellen.dealer_telefonies Order By wc.Bedrijfsnaam Select wc)
// if dropdown has value...
Dim result = objQuery.Where("MyColumnName < " + txtFilterValue1.Text);
Here's a link to the full article: Dynamic LINQ (Part 1: Using the LINQ Dynamic Query Library)