基于两个不同的数据列linq C＃的筛选列表

Question

How do I filter an item from a list based on two different columns one being a number(smallest number) using LINQ C#?

public class Line
{
   public int Id { get; set; }
   public List<LineItem> LineItems { get; set; }


  public Line()
  {
    LineItems = new List<LineItem> {
    new LineItem{Num = 1, Name="i", Qty = 0, Active = false},
    new LineItem{Num = 2, Name="j", Qty = 2,Active = false},
    new LineItem{Num = 3, Name="k", Qty = 3,Active = false},
     };
  }

}

public class LineItem
{
   public int Num { get; set; }
   public string Name { get; set; }
   public int Qty { get; set; }
   public bool Active { get; set; }
}

I want to filter this list and get a LineItem based on Qty = 0 and smallest num value.

Answer 1

You could try to get the min value for Qty is 0 and order by Num in ascending mode, then taking the first item. For sample:

var item = LineItems.Where(x => x.Qty == 0).OrderBy(x => x.Num).First();

Answer 2

Try filtering by Qty == 0 , sorting according to Num and keep the first one:

var lineItem = LineItems.Where(l => l.Qty == 0).OrderBy(l => l.Num).FirstOrDefault();

or just keep the first that Qty equals to 0 and Num equals to minimum possible:

var minNum = LineItems.Where(l => l.Qty == 0).Min(l => l.Num);
var lineItem = LineItems.FirstOrDefault(l => l.Qty == 0 && l.Num == minNum);

Answer 3

If you have your LineItem class implement IComparable<T> , then you can do something like this:

public class LineItem : IComparable<LineItem>
{
    public int Num { get; set; }
    public string Name { get; set; }
    public int Qty { get; set; }
    public bool Active { get; set; }

    public int CompareTo(LineItem other)
    {
        if (other.Num > this.Num)
            return -1;
        else if (other.Num == this.Num)
            return 0;
        else
            return 1;

    }
}

then

var item = l.LineItems.Where(p => p.Qty == 0).Min();