Linq with a long where clause

Question

Is there a better way to do this? I tried to loop over the partsToChange collection and build up the where clause, but it ANDs them together instead of ORing them. I also don't really want to explicitly do the equality on each item in the partsToChange list.

var partsToChange = new Dictionary<string, string> {
    {"0039", "Vendor A"},
    {"0051", "Vendor B"},
    {"0061", "Vendor C"},
    {"0080", "Vendor D"},
    {"0081", "Vendor D"},        
    {"0086", "Vendor D"},
    {"0089", "Vendor E"},
    {"0091", "Vendor F"},
    {"0163", "Vendor E"},
    {"0426", "Vendor B"},
    {"1197", "Vendor B"}
};

var items = new List<MaterialVendor>();
foreach (var x in partsToChange)
{
    var newItems = (
    from m in MaterialVendor 
    where 
        m.Material.PartNumber == x.Key 
        && m.Manufacturer.Name.Contains(x.Value)
    select m
    ).ToList();
    items.AddRange(newItems);
}

Additional info: I am working in LINQPad and this is a LinqToSql query. Here MaterialVendor is both a class and a DataContext Table.

Edit: LinqToSql details.

This seems to be the best method that I have found for both readability and reducing the complexity. It also has the added benefit of not having the collection type defined explicitly. That means I can vary what comes back with an anonymous type.

var predicate = PredicateBuilder.False<MaterialVendor>();

foreach (var x in partsToChange)
{
    var item = x;
    predicate = predicate.Or (m =>
        m.Material.PartNumber == item.Key 
        && m.Manufacturer.Name.Contains(item.Value));
}

var items = from m in MaterialVendor.Where(predicate)
    select m;

Answer 1

[Edit] Even better, since partsToChange is a Dictionary:

var items = MaterialVendor.Where(m =>
                m.Manufacturer.Name.Contains(partsToChange[m.Material.PartNumber])
            ).ToList();

Answer 2

Look into PredicateBuilder

This will allow you to build a Linq to sql expression within a loop, adding the clauses with AND / OR where necessary, then execute it once at the end.