Return list of custom class using Linq

Question

I have a class Author.cs as:

public class Author  
{  
   public Author()  
   { }  

   public int _AuthorID { get; set; }  
   public string _AuthorName { get; set; }  
   public List<Paper> _Papers { get; set; }  
}

and another class Paper.cs as:

public class Paper  
{  
   public Paper()  
   { }  

   public int _PaperID { get; set; }
   public List<int> _CoAuthors { get; set; }
   public int _VenueID { get; set; }
   public int _PaperCategory { get; set; }
   public int _Year { get; set; }
}  

I want to have a method in Author.cs class which returns authors for given Year and author between given Years.

I tried as following:

public List<Author> GetAuthorsByYear(List<Author> _fullList, int _year)
{
   return _fullList.Where(_author => _author.GetPaperYear() == _year).ToList();
}

public List<Author> GetAuthorsBetweenYears(List<Author> _fullList, int _startYear, int _endYear)
{
   return _fullList.Where(_author => _author.GetPaperYear() >= _startYear && _author.GetPaperYear() <= _endYear).ToList();
}  

The method GetPaperYear() is not defined yet but it is intended to define such a method in class Author.cs to achieve the goal that's why shown here as dummy.

Similarly, I want to have methods like:

public List<int> GetCoAuthorsByYear(int _year)  
{
   // How to return list of coauthors by year
}  
public List<int> GetCoAuthorsBetweenYears(int _startYear, int _endYear)  
{
   // How to return list of coauthors between years
}  

public List<int> GetVenuesByYear(int _year)  
{
   // How to return list of venues by year
}  
public List<int> GetVenuesBetweenYears(int _startYear, int _endYear)  
{
   // How to return list of venues between years
}

How to achieve this using Linq?

Answer 1

If you want to have separate method in the Author class like you asked in the question, it could look like:

public class Author
{
    public Author()
    { }

    public int _AuthorID { get; set; }
    public string _AuthorName { get; set; }
    public List<Paper> _Papers { get; set; }

    public bool HasPapersForYear(int year)
    {
        return _Papers.Any(_paper => _paper._Year == year);
    }

    public bool HasPapersForYears(int startYear, int endYear)
    {
        return _Papers.Any(_paper => _paper._Year >= startYear && _paper._Year <= endYear);
    }
}

And old methods are changed:

public List<Author> GetAuthorsByYear(List<Author> _fullList, int _year)
{
    return _fullList.Where(_author => _author.HasPapersForYear(_year)).ToList();
}

public List<Author> GetAuthorsBetweenYears(List<Author> _fullList, int _startYear, int _endYear)
{
    return _fullList.Where(_author => _author.HasPapersForYears(_startYear,_endYear)).ToList();
} 

Also about the part of Venue and CoAuthors

    public List<int> GetCoAuthorsByYear(int _year)
    {
        var coAuthors = new List<int>();
        foreach(var paper in _Papers.Where(_paper => _paper._Year == _year))
        {
            coAuthors.AddRange(paper._CoAuthors);
        }
        return coAuthors;
    }
    public List<int> GetCoAuthorsBetweenYears(int _startYear, int _endYear)
    {
        var coAuthors = new List<int>();
        foreach(var paper in _Papers.Where(_paper => _paper._Year >= _startYear && _paper._Year <= _endYear))
        {
            coAuthors.AddRange(paper._CoAuthors);
        }
        return coAuthors;
    }

    public List<int> GetVenuesByYear(int _year)
    {
        var venues = new List<int>();
        foreach(var paper in _Papers.Where(_paper => _paper._Year == _year))
        {
            venues.Add(paper._VenueID);
        }
        return venues;
    }
    public List<int> GetVenuesBetweenYears(int _startYear, int _endYear)
    {
        var venues = new List<int>();
        foreach(var paper in _Papers.Where(_paper => _paper._Year >= _startYear && _paper._Year <= _endYear))
        {
            venues.Add(paper._VenueID);
        }
        return venues;
    }       

This code could be refactored sure.