Question

我有一个班级Author.cs：

public class Author  
{  
   public Author()  
   { }  

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

和另一个班级Paper.cs：

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; }
}

我希望在Author.cs类中有一个方法，它返回给定年份的作者和给定年份之间的作者。

我尝试了以下内容：

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();
}

方法GetPaperYear()尚未定义，但它旨在在类Author.cs中定义此类方法，以实现此处显示为虚拟的目标。

同样，我希望有类似的方法：

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
}

如何使用Linq实现这一目标？

Answer 1

使用Linq比您已经使用的更深，并将return语句更改为：

在GetAuthorsByYear()方法中：

return _fullList.Where(_author => _author._Papers.Any(y => y._Year == _year)).ToList();

在GetAuthorsBetweenYears()方法中：

return _fullList.Where(_author => _author._Papers.Any(y => y._Year >= _startYear && y._Year <= _endYear))).ToList();

不再需要方法GetPaperYear()。

Answer 2

如果你想在问题中提到的Author类中有单独的方法，它可能看起来像：

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);
    }
}

旧方法改变了：

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();
}

还有关于Venue和CoAuthors的部分

    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;
    }

此代码可以重新确定。

使用Linq

2 个答案: