C# Enumerable SelectMany(IEnumerable, Func>, Func)
Description
Projects
each element of a sequence to an IEnumerable
Syntax
public static IEnumerable<TResult> SelectMany<TSource, TCollection, TResult>(
this IEnumerable<TSource> source,
Func<TSource, IEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, TResult> resultSelector
)/* w w w . j a va2s . c om*/
Parameters
TSource- The type of the elements of source.TCollection- The type of the intermediate elements collected by collectionSelector.TResult- The type of the elements of the resulting sequence.source- A sequence of values to project.collectionSelector- A transform function to apply to each element of the input sequence.resultSelector- A transform function to apply to each element of the intermediate sequence.
Example
The following code example demonstrates how to use SelectMany to perform a one-to-many projection over an array and use a result selector function to keep each corresponding element from the source sequence in scope for the final call to Select.
/*from w w w . j a v a2s . com*/
using System;
using System.Linq;
using System.Collections.Generic;
public class MainClass{
public static void Main(String[] argv){
PetOwner[] petOwners ={ new PetOwner { Name="A",
Pets = new List<string>{ "a", "b" } },
new PetOwner { Name="B", Pets = new List<string>{ "c", "d" } },
new PetOwner { Name="C",Pets = new List<string>{ "e", "f" } },
new PetOwner { Name="D", Pets = new List<string>{ "S" } } };
var query = petOwners
.SelectMany(petOwner => petOwner.Pets, (petOwner, petName) => new { petOwner, petName })
.Where(ownerAndPet => ownerAndPet.petName.StartsWith("S"))
.Select(ownerAndPet =>new{
Owner = ownerAndPet.petOwner.Name,
Pet = ownerAndPet.petName
}
);
foreach (var obj in query)
{
Console.WriteLine(obj);
}
}
}
class PetOwner{
public string Name { get; set; }
public List<string> Pets { get; set; }
}