Question

Hello – I’m trying to get a where condition to apply to a sub collection. I can get the criteria to return the proper parents. However, I want the sub collection to be limited to the criteria as well.

In my example code, I only want people with “LINK” skills; also, I only want the skills for each person to equal “LINK.” That is, each person should only have “LINK” for their skills.

Thanks in advance.

List<Skill> skills = new List<Skill>();
skills.Add(new Skill(){SkillName="ASP.NET"});
skills.Add(new Skill(){SkillName="C#"});
Person p1 = new Person(){ Name="Me", Skills=skills} ;

List<Skill> skills2 = new List<Skill>();
skills2.Add(new Skill(){SkillName="ASP.NET"});
skills2.Add(new Skill(){SkillName="C#"});
skills2.Add(new Skill(){SkillName="LINQ"});
Person p2 = new Person(){ Name="You", Skills=skills2} ;

List<Person> People = new List<Person>();
People.Add(p1);
People.Add(p2);

var oResult = (from item in People
    from sk in item.Skills
    where sk.SkillName == "LINQ" 
    select item 
    ).ToList();

When I run this. I get p2 (correct), but I want the skills of P2 to only equal LINQ

Answer 1

Do this:

var oResult = (from item in People
                where item.Skills.Count() == 1 &&
                item.Skills.Any(s => s.SkillName == "LINQ")
                select item
    ).ToList();

This query will return nothing because p2 (You) has other skills in addition to LINQ.

You can do what you want this way:

foreach (var person in oResult)
{
    person.Skills.RemoveAll(s => !s.SkillName.Equals("LINQ"));
}

Note: while using LINQ you’re only filtering your data. To post process it you use something like the foreach I show you above.