Entity Framework : Filter nested collection by value of its properties

问题

I have model as below

class MyClass()
{
   public int Id { get; set; }
   public List<Item> Items { get; set; }
}

class Item
{
     public int Id { get; set; }
     public string Name { get; set; }
}

both are added to DBContext as DbSets, now I would like to filter out the MyClass using the value of the Name property in the Items collection. How do I do this?

回答1:

First of all correct your POCOs this way:

public class MyClass
{
   public int Id { get; set; }
   public virtual ICollection<Item> Items { get; set; }
}

public class Item
{
   public int Id { get; set; }
   public string Name { get; set; }

   public virtual MyClass MyClass {get;set}
   public int MyClassId {get;set}
}

Usage:

Presented query will return all MyClass instances, where at least one item's Name will satisfy condition:

var answer = db.MyClass.Where(c => c.Items.Any(item => item.Name == "Sam")).ToList();

This query will return all MyClass instances, where all item's Name will satisfy condition:

var answer = db.MyClass.Where(c => c.Items.All(item => item.Name == "Sam")).ToList();

来源：https://stackoverflow.com/questions/47002517/entity-framework-filter-nested-collection-by-value-of-its-properties