Comparing values of arrays in C#

Question

I have a bool array that looks like this

bool[] responses = new bool[] {true, false, true};

And two classes that look like this:

public class Person {
  public IList<PersonDetail> PersonDetails
}

public class PersonDetail {
  public bool   Correct { get; set; }
}

PersonDetails
 >> PersonDetail[0].correct = true
 >> PersonDetail[1].correct = true
 >> PersonDetail[2].correct = false

Is there a simple way I can compare these to see if the true/false are equal for each? I was trying to use the c# .SequenceEqual but I don't know how to get the data from the PersonDetail class into a sequence xxx that I can use to compare with responses.

Here's what I have so far:

var equal = responses.Select(bool.Parse).SequenceEqual( xxx );

What I need to do is to compare the following:

responses[0] == PersonDetail[0].correct and
responses[1] == PersonDetail[1].correct and
responses[2] == PersonDetail[2].correct

So what's true in responses[x] should match true in PersonDetail[x] and what's false in responses[x] should match false in PersonDetail[x]

A lil bit confusing here. Do you want to compare if the Person array have a repeated items? — Zenwalker
– Zenwalker, Commented Jun 15, 2011 at 8:14
Surely this is for-loop territory, I don't see how linq could do anything but slow it down? — user159335
– user159335, Commented Jun 15, 2011 at 8:19
"I have a string array that looks like this"... nope, it's a bool array. — Heinzi
– Heinzi, Commented Jun 15, 2011 at 8:23

Freek · Accepted Answer · 2011-06-15 08:25:49Z

1

Your code isn't really clear, but I imagine you want to do the following:

var isEqual = responses.SequenceEqual(PersonDetail.Select(p=>p.Correct))

edited Jun 15, 2011 at 8:25

answered Jun 15, 2011 at 8:14

Freek

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2 Comments

Zenwalker Over a year ago

Cant the logical AND/OR operation be done, since they are bool type? I think thats much faster and efficient! :)

czhili Over a year ago

@zenwalker - I added some more to the question. Hope it explains it better. Thanks

Jonas Elfström · Accepted Answer · 2011-06-15 08:43:22Z

1

You can use SequenceEqual like this

var responses = new [] { true, false, true };
var details = new List<PersonDetail>()
                { new PersonDetail() {Correct = true},
                  new PersonDetail() {Correct = false},
                  new PersonDetail() {Correct = true} };
var person = new Person() { PersonDetails = details };

var equal = responses.SequenceEqual(person.PersonDetails.Select(pd => pd.Correct));

answered Jun 15, 2011 at 8:43

Jonas Elfström

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Comments

Harag · Accepted Answer · 2011-06-15 08:47:52Z

From the answers already given I've had a play around and come up with the below, seems to work - note that I'm also new to C# so this has been an interesting problem.

As JonB points out in one of the answers - what happens if the lengths of "responses" and "people" are different... Hope the below helps

class Program
{       
    static void Main(string[] args)
    {
        bool[] responses = new bool[] { true, false, true };

        Person people = new Person();
        people.PersonDetails.Add(new PersonDetail() { Correct = true });
        people.PersonDetails.Add(new PersonDetail() { Correct = false });
        people.PersonDetails.Add(new PersonDetail() { Correct = true });

        bool equal = responses.SequenceEqual(people.PersonDetails.Select(P=> P.Correct));
        Console.WriteLine (equal);
    }
}

public class Person
{
    public List<PersonDetail> PersonDetails = new List<PersonDetail>();
}

public class PersonDetail
{
    public bool Correct;
}

MarcE · Accepted Answer · 2011-06-15 08:53:37Z

1

If I'm reading your question correctly, this LINQ will do what you ask. I'm not sure it's more readable than a simple foreach loop but that's not the point!

public class Person 
{
  public IList<PersonDetail> PersonDetails;
}

public class PersonDetail 
{
  public bool   Correct;
}

void Main()
{
    bool[] responses = new bool[] {true, false, true};
    Person p = new Person();
    p.PersonDetails = new List<PersonDetail>();
    p.PersonDetails.Add(new PersonDetail(){Correct = true});
    p.PersonDetails.Add(new PersonDetail(){Correct = true});
    p.PersonDetails.Add(new PersonDetail(){Correct = false});

    //bool allGood = p.PersonDetails.Select((pd, index) => pd.Correct == responses[index]).All(x => x==true);

    bool allGood = responses.SequenceEqual(p.PersonDetails.Select(x => x.Correct));
    allGood.Dump(); // LINQpad extension
}

[edit - OK, so it's early and I forgot about SequenceEquals which does the same thing in a much more readable manner. Code changed to match what everyone else already answered...].

edited Jun 15, 2011 at 8:53

answered Jun 15, 2011 at 8:41

MarcE

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1 Comment

MarcE Over a year ago

It's all relative - I'm not sure the LINQ is more readable than a for loop (if you don't know LINQ anyway) but the second LINQ is more readable than the first!

George Duckett · Accepted Answer · 2011-06-15 08:26:54Z

0

Not 100% sure of your code, but maybe:

var equal = responses.SequenceEqual(Person.PersonDetails.Select(PD => PD.correct);

edited Jun 15, 2011 at 8:26

answered Jun 15, 2011 at 8:15

George Duckett

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4 Comments

czhili Over a year ago

I added some more to the question. Hope it explains it better. Thanks

czhili Over a year ago

I don't think this will work because I have the class Person that contains PersonDetail classes in a list called PersonDetails. The flag I want to compare responses to is a field in the PersonDetail class.

czhili Over a year ago

Thanks for the edit. When I run your suggestion I get an error message saying: An object reference is required for the non-static field, method or property Person.PersonDetails.get

George Duckett Over a year ago

@czhili, Replace Person with the name of your Person variable.

Patrick · Accepted Answer · 2011-06-15 08:35:15Z

0

You could also try something like this:

IEnumerable<bool> answers = from x in Person.PersonDetails select x.correct;
bool equal = responses.SequenceEqual(answers)

answered Jun 15, 2011 at 8:35

Patrick

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Comments

score 0 · Accepted Answer · 2011-06-15 08:57:50Z

0

Doesn't get much simpler than:-

  if (person.PersonDetails.Count != responses.Length)
    throw new ArgumentOutOfRangeException("Arrays are different lengths");
  bool result = true;
  for (int i = 0; i < person.PersonDetails.Count; i++)
  {
    if (person.PersonDetails[i].Correct != responses[i])
    {
      result = false;
      break;
    }
  }

Every programmer on the planet will be able to read it, even if they've never seen c#.

Actually it highlights a missing aspect of the spec; What should happen if the lists are different lengths?

edited Jun 15, 2011 at 8:57

answered Jun 15, 2011 at 8:35

user159335

6 Comments

Patrick Over a year ago

If responses is shorter than person.PersonDetails however, you will get an error, so it does not address that aspect of the spec.

user159335 Over a year ago

I'm not sure that "fancy" is really an objective in programming. There's a tendency towards spectacular flourishes when we're really after something that finishes quickly and can be read by a dog.

user159335 Over a year ago

@Patrick I did mention that it highlights a missing aspect of the spec. Whilst it could return a value, should that be true or false? Since we don't know an error is valid.

czhili Over a year ago

Checked this out and it works. I think there is probably a one liner answer some place but this one does work :-) responses and person.PersonDetails are always the same length.

Patrick Over a year ago

Ah sorry, I thought that you meant it addressed that aspect. It definitely raises the question, as SequenceEqual will just return false

|

Shawn Chin · Accepted Answer · 2011-06-27 16:38:17Z

0

Use XOR and not AND or OR operations on these items. XOR table will give you 0 if both items are the same.

edited Jun 27, 2011 at 16:38

Shawn Chin

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answered Jun 15, 2011 at 8:27

Zenwalker

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