Ling应用

SelectMany

一个序列的每个元素投影, 将平展为一个序列。结果延迟执行。

PetOwner[] petOwners ={
	new PetOwner { Name="Higa, Sidney",Pets = new List<string>{ "Scruffy", "Sam" } },
	new PetOwner { Name="Ashkenazi, Ronen",Pets = new List<string>{ "Walker", "Sugar" } },
	new PetOwner { Name="Price, Vernette",Pets = new List<string>{ "Scratches", "Diesel" } },
	new PetOwner { Name="Hines, Patrick",Pets = new List<string>{ "Dusty" } } };
// 子集投影
var pets = petOwners.SelectMany(s => s.Pets);
// 嵌套转平铺展示
var query = petOwners.SelectMany(s => s.Pets, (s, section) => new
{
    s.Name,
    Pet = section,
});
foreach (var item in query)
{
    Console.WriteLine(item.Name + ": " + item.Pet);
}
// 添加索引
var query2 = petOwners.SelectMany((s, i) =>
    s.Pets.Select(x =>
    {
        x= $"{i},{x}";
        return x;
    }));
// 添加索引
var query3 = petOwners.SelectMany((s, i) =>
{
  for(int j = 0; j < s.Pets.Count; j++)
  {
      s.Pets[j] = $"{i}-{s.Pets[j]}";
  }
  return s.Pets;
}, (s, x) => new 
{
  s.Name,
  PetName = x,
});