Question

我无法使用LINQ概念化一些相当简单的东西。我有一个集合，我想根据子对象的id值缩小或过滤。

我的主要收藏品包括一个斑点列表。这就是现场的样子：

public class Spot
{
    public virtual int? ID { get; set; }
    public virtual string Name { get; set; }
    public virtual string Description { get; set; }
    public virtual string TheGood { get; set; }
    public virtual string TheBad { get; set; }
    public virtual IEnumerable<Season> Seasons { get; set; }
    public virtual IEnumerable<PhotographyType> PhotographyTypes { get; set; }
}

我正在尝试按照摄影类型和季节来过滤斑点列表。我有一个关于PhotographyTypes和Seasons的id列表，每个都在int []数组中。这些列表如下所示：

criteria.PhotographyTypeIds //an int[]
criteria.SeasonIds //an int[]

我想构建一个只包含Spots的集合，其子对象（id）与上面列表中的对象匹配。此功能的目标是按类型和季节过滤一组摄影点，并仅显示匹配的那些。任何建议将不胜感激。

Answer 1

感谢大家的建议。我最终解决了这个问题。这不是我确定的最佳方式，但它现在正在运作。因为这是一个搜索过滤器，所以有很多条件。

private List<Spot> FilterSpots(List<Spot> spots, SearchCriteriaModel criteria)
    {
        if (criteria.PhotographyTypeIds != null || criteria.SeasonIds != null)
        {
            List<Spot> filteredSpots = new List<Spot>();

            if (criteria.PhotographyTypeIds != null)
            {
                foreach (int id in criteria.PhotographyTypeIds)
                {
                    var matchingSpots = spots.Where(x => x.PhotographyTypes.Any(p => p.ID == id));
                    filteredSpots.AddRange(matchingSpots.ToList());
                }
            }

            if (criteria.SeasonIds != null)
            {
                foreach (int id in criteria.SeasonIds)
                {
                    if (filteredSpots.Count() > 0)
                    {
                        filteredSpots = filteredSpots.Where(x => x.Seasons.Any(p => p.ID == id)).ToList();
                    }
                    else
                    {
                        var matchingSpots = spots.Where(x => x.Seasons.Any(p => p.ID == id));
                        filteredSpots.AddRange(matchingSpots.ToList());
                    }
                }
            }
            return filteredSpots;
        }
        else
        {
            return spots;
        }
    }

Answer 2

这可能会对您有所帮助：

List<Spot> spots = new List<Spot>();
Spot s1 = new Spot();
s1.Seasons = new List<Season>() 
             { new Season() { ID = 1 }, 
               new Season() { ID = 2 }, 
               new Season() { ID = 3 } 
             };
s1.PhotographyTypes = new List<PhotographyType>() 
             { new PhotographyType() { ID = 1 }, 
               new PhotographyType() { ID = 2 } 
             };

Spot s2 = new Spot();
s2.Seasons = new List<Season>() 
             { new Season() { ID = 3 }, 
               new Season() { ID = 4 }, 
               new Season() { ID = 5 } 
             };
s2.PhotographyTypes = new List<PhotographyType>() 
             { new PhotographyType() { ID = 2 }, 
               new PhotographyType() { ID = 3 } 
             };

List<int> PhotographyTypeIds = new List<int>() { 1, 2};
List<int> SeasonIds = new List<int>() { 1, 2, 3, 4 };

spots.Add(s1);
spots.Add(s2);

然后：

var result = spots
             .Where(input => input.Seasons.All
                           (i => SeasonIds.Contains(i.ID)) 
                    && input.PhotographyTypes.All
                           (j =>  PhotographyTypeIds.Contains(j.ID))
                    ).ToList();
// it will return 1 value

假设：

public class Season
{
    public int ID { get; set; }
    //some codes
}
public class PhotographyType
{
    public int ID { get; set; }
    //some codes
}

Answer 3

您有一系列具有Contains扩展名的ID，当ID在列表中时，该方法将返回true。结合LINQ Where，您将得到：

List<Spot> spots;   // List of spots
int[] seasonIDs;    // List of season IDs

var seasonSpots = from s in spots
                  where s.ID != null
                  where seasonIDs.Contains((int)s.ID)
                  select s;

如果需要，您可以将返回的IEnumerable<Spot>转换为列表：

var seasonSpotsList = seasonSpots.ToList();

LINQ查询按多个列表中的条件筛选项目

3 个答案: