Convert object to string using Linq

Question

I am trying to convert object to a string using SelectMany. However when list property value is empty then I am not getting desired string.

I am expecting results like

name1-2-4 : name2-

but getting this result as

name1-2-4

. The second name is ignored because of "Scores" list which is empty.

using System;
using System.Linq;
using System.Collections.Generic;
                    
public class Program
{
    public static void Main()
    {
        var person1 = new Person()
        {
            Name = "name1",
            Scores = new List<Score>
            {
                new Score
                {
                    InitialScore =2,
                    UpdatedScore = 4
                }
            }
        };

        var person2 = new Person()
        {
            Name = "name2",
            Scores = new List<Score>()
        };

        var persons = new List<Person>();
        persons.Add(person1);
        persons.Add(person2);       
                
        var result = string.Join(" : ", persons.SelectMany(x=>x.Scores, (parent, child)=> parent.Name + "-" + child.InitialScore +"-"+ child.UpdatedScore));
        Console.WriteLine(result);
    }
}

public class Person
{
    public string Name {get; set;}
    public List<Score> Scores {get; set;}
}

public class Score
{
    public int InitialScore {get; set;}
    public int UpdatedScore {get; set;}
}

Edit: Based on @JonasH solution use this linq query.

var result = string.Join(" : ", persons.SelectMany(x=>GetNames(x)));

JonasH · Accepted Answer · 2021-05-04 06:38:04Z

1

A simple solution would be to add a helper method to your person that does what you want:

    public static IEnumerable<string> GetNames(this Person p)
    {
        if (p.Scores.Count == 0)
        {
            yield return p.Name;
        }
        else
        {
            foreach (var score in p.Scores)
            {
                yield return $"{p.Name}-{score}";
            }
        }
    }

and use that instead of .Scores in SelectMany.

edited May 4, 2021 at 6:38

answered May 3, 2021 at 14:33

JonasH

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2 Comments

PSR Over a year ago

unfortunately, not allowed to change those classes.

JonasH Over a year ago

@PSR then just make it an extension method.

Peter Csala · Accepted Answer · 2021-05-04 07:30:32Z

1

var result1 = persons.SelectMany(x => x.Scores, (parent, child) => parent.Name + "-" + child.InitialScore + "-" + child.UpdatedScore).FirstOrDefault();

var result2 = persons.Where(x => x.Scores.Count() <= 0).Select(x => x.Name).FirstOrDefault()+"-";
            
var result = $"{result1}:{result2}";

edited May 4, 2021 at 7:30

Peter Csala

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answered May 3, 2021 at 15:01

biksh49

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1 Comment

Peter Csala Over a year ago

Welcome to StackOverflow. Please provide explanation as well not just code.

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