Linq Max()

string keyword = "michio kaku";
using (MyModelEntities db = new MyModelEntities()) 
{        
        long? maxId = db.ResultDatas.Select(m => m.Query == Keyword).Max(m => db.ResultDatas.Max(r => r.ResultId)); 
}

In the code above, I have an Entity Set named "ResultDatas" with some fields "Query" and "ResultId".

The underlying data store could have 0 to n matches for a given query. I want to return the max(ResultId) of the matched keyword (or null for non-matched sets).

The code above works, but seems ineffecient, can someone explain a better way to do this?

TIA

Turns out the query I was using above was completly wrong to begin with.

long? maxId = db.ResultDatas.Where(model => model.Query == Keyword).Max(res => (long?)res.ResultId) ?? 0;

The above code works, is intuitive and seems to be reasonably performant.

If anyone knows any better please let me know!