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How to flatten a list using LINQ C#?
Flattening a list means converting a List<List<T>> to List<T>. For example, let us consider a List<List<int>> which needs to be converted to List<int>.
The SelectMany in LINQ is used to project each element of a sequence to an IEnumerable<T> and then flatten the resulting sequences into one sequence. That means the SelectMany operator combines the records from a sequence of results and then converts it into one result.
Using SelectMany
Example
using System;
using System.Collections.Generic;
using System.Linq;
namespace DemoApplication{
public class Program{
static void Main(string[] args){
List<List<int>> listOfNumLists = new List<List<int>>{
new List<int>{
1, 2
},
new List<int>{
3, 4
}
};
var numList = listOfNumLists.SelectMany(i => i);
Console.WriteLine("Numbers in the list:");
foreach(var num in numList){
Console.WriteLine(num);
}
Console.ReadLine();
}
}
}Output
Numbers in the list: 1 2 3 4
Using Query
Example
using System;
using System.Collections.Generic;
using System.Linq;
namespace DemoApplication{
public class Program{
static void Main(string[] args){
List<List<int>> listOfNumLists = new List<List<int>>{
new List<int>{
1, 2
},
new List<int>{
3, 4
}
};
var numList = from listOfNumList in listOfNumLists
from value in listOfNumList
select value;
Console.WriteLine("Numbers in the list:");
foreach(var num in numList){
Console.WriteLine(num);
}
Console.ReadLine();
}
}
}Output
Numbers in the list: 1 2 3 4
Updated on: 24-Sep-2020
4K+ Views
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