LINQ to Object Query

Question

I need help with a specific LINQ query (I still suck at em'!)

Background Info:

I've got a class DataEntry:

class DataEntry{
    public Attribute Attribute{get; set;}
    public List<object> Data{get; set;}

Attribute Class:

class Attribute{
    public string FeatureName{get; set;}
    public Types FeatureType{get; set;}
    public List<object> PossibleValues{get; set;}

What i'll eventually have is about ~20 different data entries with about 1000 data objects per entry. What I'm trying to do is write a LINQ query to select a specific data entry based on the FeatureType and then give me a count of the total number of data items of that entry equal to a specific value.

What i'm trying to get is the count of the "high" and count of the "low" values from the data entry that has a featuretype equal to "foobar".

The closest I've gotten is:

int count = dataset.SelectMany(i => i.Data).Count(j => j.ToString() == "high");

Which gives me the count of "high", but doesn't filter by featuretype.

Is it possible? Is it possible to do in a single statement?

Answer 1

You are on the right track. Just add a Where method to filter out stuff before feeding them to SelectMany.

dataset.Where(i => i.Attribute.FeatureType == Types.FooBar)
       .SelectMany(i => i.Data)
       .Count(j => j.ToString() == "high")

To calculate high and low in a single statement, you can try:

dataset.Where(i => i.Attribute.FeatureType == Types.FooBar)
       .SelectMany(i => i.Data)
       .Select(i => i.ToString())
       .Aggregate(new { High = 0, Low = 0 },
            (acc, i) => val == "high" ? new { High = i.High + 1, i.Low }
                      : val == "low"  ? new { i.High,  Low = i.Low + 1 } : acc);

Answer 2

Another way:

int count = 
( from dataEntry in dataset
  from data in dataEntry.Data
  where dataEntry.Attribute.FeatureType == Types.Foo && data.ToString() == "high"
  select data
).Count();