Question

I’m working on my first project using LINQ (in mvc), so there is probably something very simple that I missed. However, a day of searching and experimenting has not turned up anything that works, hence the post.

I’m trying to write a LINQ query (Linq to SQL) that will contain a multiple number of conditions in the where statement separated by an OR or an AND. We don’t know how many conditions are going to be in the query until runtime. This is for a search filter control, where the user can select multiple criteria to filter by.

select * from table
where table.col = 1 
    OR table.col = 2
    OR table.col = 7
    .... 'number of other conditions

Before I would just construct the SQL query as a string while looping over all conditions. However, it seems like there should be a nice way of doing this in LINQ.
I have tried looking using expression trees, but they seem a bit over my head for the moment. Another idea was to execute a lambda function inside the where statement, like so:

For Each value In values
    matchingRows = matchingRows.Where(Function(row) row.col = value)

However, this only works for AND conditions. How do I do ORs?

Answer 1

I would use PredicateBuilder for this. It makes dynamic WHERE clauses very easy.