Question 87688 in ASP.NET Question posted in
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Combining contents of 2 lists in C# – Asp.net

I just started learning C#. I want to combine 2 lists and return the output. For example:

List 1 = Peter, Tony, Steve
List 2 = Parker, Stark, Rogers

Final List/Output:
Peter Parker
Tony Stark
Steve Rogers

Here is my codes:

using System;
using System.Collections.Generic;
using System.Linq;

namespace HelloWorld
{
    class Program
    {
        static void Main(string[] args)
        {
            var projectTeam = "Group Avengers";
            Console.WriteLine("Avengers Assemble");

            string[] firstNames = {"Peter", "Tony", "Steve"};
            string[] lastNames = {"Parker", "Stark", "Rogers"};
            IList<string> combinedNames = new List<string>();

            foreach (string firstName in firstNames)
            {
                foreach (string lastName in lastNames)
                {
                    Console.WriteLine(firstName + lastName);
                }
            }
        }
    }
}

Actual Output:

Avengers Assemble
PeterParker
PeterStark
PeterRogers
TonyParker
TonyStark
TonyRogers
SteveParker
SteveStark
SteveRogers

Expected Output:

Avengers Assemble
Peter Parker
Tony Stark
Steve Rogers
Tags:

6

Answers


  1. 0

    In your code you need only one loop and it should be for, not foreach

            for (var i = 0; i< firstNames.Length; i++)
        {
            string firstName = firstNames[i];
            string lastName = lastNames[i];
            Console.WriteLine(firstName + lastName);
        }

    You can also replace this with IEnumerable.Zip (https://learn.microsoft.com/en-us/dotnet/api/system.linq.enumerable.zip?view=net-6.0)

            firstNames
            .Zip(lastNames, (first, last) => first + last)
            .ToList()
            .ForEach(x=>Console.WriteLine(x));

    Please note that both approaches assumes that both firstNames and lastNames has the same number of elements.

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  2. 0

    This can be done with LINQ Zip():

    var fullNames = firstNames.Zip(lastNames, (first, last) => $"{first} {last}")

    Zip takes the two lists and runs through both of them simultaneously, applying the function to each pair.

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  3. 0

    You could use a for-loop and access the lists via index:

    for(int i = 0; i < Math.Min(firstNames.Length, lastNames.Length); i++)
{
    Console.WriteLine(firstNames[i] + lastNames[i]);
}

    better would it be to store the two related information in a common class, for example Avenger with properties FirstName and LastName.

    Another way to link two related lists is LINQ’s Zip:

    var zippedAvengers = firstNames.Zip(lastNames, (f,l) => f + " " + l);
foreach(string name in zippedAvengers)
    Console.WriteLine(name);
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  4. 0

    If you alter the loop:

        for (int i=0; i < firstNames.Count; i++)
    {
         Console.WriteLine(firstNames[i] + " " + lastNames[i]);
    }

    It’ll work.

    As a side note – in newer versions on .NET you can simplify the concatenation with $"{firstNames[i]} {lastNames[i]}"

    Plus, the .Zip solution (as proposed by Serg):

    firstNames
   .Zip(lastNames, (first, last) => first + " " + last)
   .ToList()
   .ForEach(x=>Console.WriteLine(x));

    Would be more efficient

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  5. 0

    What you are doing is you’re matching every element of the first list with every element of the second list. But what you wanna do, if I get you right, is to match the first element of the first list with the first element of the second list.

    In order to do that, I won’t give you the code so you can learn but I can show you where to go :

    1. Make sure your lists are both the same size, otherwise you will get an exception trying to access an inexisting index
    2. Use for loop instead of foreach, they are less instinctive but more useful in this situation. For each index of the two lists, make the same index of the third list (the result) correspond to the concatenation of the two, for example :
    result[0] = firstList[0] + secondList[0];

    (In order to have a space between the two, you must add a space between the first and the second list item)

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  6. 0

    You are running two for loops for no reason. Just run one single loop from i = 0 to i = 3(not included).Then you can pick the ith element from both the lists.
    Example. for i = 0, firstNames[0] = "Peter" lastNames[0] = "Parker"
    You can print

    Console.WriteLine(firstNames[i] + " " + lastNames[i]);

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