CODEWITHSUNDEEP
c#asp.net.netlinq
Casey Crookston
Casey Crookston

Reputation: 13955

Use LINQ to remove items in List<object> where a property exists in List<string>

This question is very similar to this one: Use LINQ to get items in one List<>, that are not in another List<>. But the differences are just enough that I'm having trouble nailing down the LINQ syntax.

I have two lists:

List<Fubar> fewBarNew
List<string> existingProviderIDs

Where Fubar looks like:

Class Fubar
{
    int FunbarId int {get; set;}
    ....
    ....
    string ProviderID {get; set;}
}

Now, I want to remove from fewBarNew any instance where FewBarNew.ProviderID exists inside existingProviderIDs.

 fewBarNew = fewBarNew.Where(f => !existingProviderIdList.Any(ep => ?????).ToList();

Upvotes: 0

Views: 522

Answers (1)

Gilad Green
Gilad Green

Reputation: 37299

Any enables you to check if any item in a collections matches some predicate. So you could define the predicate to be "if any item matches the current":

fewBarNew.Where(f => !existingProviderIdList.Any(ep => ep == f.ProviderID));

However, I think a cleaner way will be to use .Contains:

var result = fewBarNew.Where(f => !existingProviderIDs.Contains(f.ProviderID));

Then, as this performs in O(n^2) you can improve using a HashSet<string> instead:

var existingProviderIDSet = new HashSet<string>(existingProviderIDs);
var result = fewBarNew.Where(f => !existingProviderIDSet.Contains(f.ProviderID));

As HashSet's Contains performs an O(1) operation, this will execute in O(n).

Upvotes: 6

Related Questions