Linq基于公共字段将子实体附加到PArent

// 假设有两个实体类 Parent 和 Child，它们之间通过共享的字段进行关联
class Parent
{
    public int Id { get; set; }
    public string Name { get; set; }
}

class Child
{
    public int ParentId { get; set; }
    public string ChildName { get; set; }
}

// 创建一个父实体集合和一个子实体集合
List<Parent> parents = new List<Parent>
{
    new Parent { Id = 1, Name = "Parent 1" },
    new Parent { Id = 2, Name = "Parent 2" }
};

List<Child> children = new List<Child>
{
    new Child { ParentId = 1, ChildName = "Child 1" },
    new Child { ParentId = 2, ChildName = "Child 2" },
    new Child { ParentId = 1, ChildName = "Child 3" }
};

// 使用Linq查询语句将子实体附加到对应的父实体
var query = from parent in parents
            join child in children on parent.Id equals child.ParentId into childGroup
            select new
            {
                Parent = parent,
                Children = childGroup
            };

// 遍历查询结果并输出
foreach (var result in query)
{
    Console.WriteLine($"Parent: {result.Parent.Name}");
    foreach (var child in result.Children)
    {
        Console.WriteLine($"Child: {child.ChildName}");
    }
    Console.WriteLine();
}