Retrieve object from an arraylist with a specific element value

Question

I have a class with some attributes. For example class person with name, age, gender and so on as attribute.

People fill out a form, with among other things their gender which is a dropdownlist, they submit it and the person is added to the arraylist.

What I need is a function by clicking a button to display all the persons who chose Female as gender.

Can somebody please help me? I have tried and searched for the right answer for days now and getting a little desperat now.

Many thanks!!!

Olaf

This is my .cs code

    public class Person
{
    private string name;
    private string artistname;
    private string address;
    private double number;
    private double zip;
    private string day;
    private string gender;

public Person(string name, string artistname, string address, double number, double zip, string day, string gender)
    {
        this.name = name;
        this.artistname = artistname;
        this.address = address;
        this.number = number;
        this.zip = zip;
        this.day = day;
        this.gender = gender;
    }

    public override string ToString()
    {
        string newPerson = name + " aka " + artistname + " lives on " + address + " " + number + " " + zip + " " + day + "Gender: " + gender;
        return newPerson;
    }
}

And this is my .aspx code:

public partial class Index : System.Web.UI.Page
{
    static ArrayList personArrayList;

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            personArrayList = new ArrayList();
        }
    }

    protected void btnSubmit_Click(object sender, EventArgs e)
    {
        Person p = new Person(txtName.Text, txtArtistName.Text, txtAddress.Text, Convert.ToDouble(txtNumber.Text), Convert.ToDouble(txtPostal.Text), Convert.ToString(dropdownDay.Text), Convert.ToString(dropdownGender.Text));
        personArrayList.Add(p);
    }

    protected void btnShowAll_Click(object sender, EventArgs e)
    {
        ListBoxShow.Items.Clear();
        for (int i = 0; i < personArrayList.Count; i++)
        {
            ListBoxShow.Items.Add(personArrayList[i].ToString());
        }
    }

    protected void btnShowGentle_Click(object sender, EventArgs e)
    {
        ListBoxShow.Items.Clear();

    }

    protected void btnShowLadies_Click(object sender, EventArgs e)
    {
        ListBoxShow.Items.Clear();
        for (int i = 0; i < personArrayList.Count; i++)
        {
            if (personArrayList[i].gender = "Female")
            {

            }
        }
    }
}

Why not use something like SQLite so you can use the built in database features to do this for you? — Austin T French
– Austin T French, Commented Oct 19, 2013 at 19:11

user · Accepted Answer · 2013-10-19 19:56:30Z

2

The C# way is to take usage of LINQ to query collections, as such:

var persons = personArrayList.AsQueryable();
var females = persons.Where(p => p.gender.Equals("Female"));

edited Oct 19, 2013 at 19:56

answered Oct 19, 2013 at 19:22

user

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6 Comments

Napivo Over a year ago

I know this does not work as this is an ArrayList and not a List<Person> but I wonder can you translate the full query like I use it to this format? "from Person P in personArrayList where P.Gender == "Female" select P;"

Napivo Over a year ago

in your case my compiler can't find out what type p is. so it can never get to p.gender... could it be because I use .net 3.5 here?

user Over a year ago

You need to type your arraylist: personArrayList = new ArrayList<Person>();

Napivo Over a year ago

Yea but from the soure code it is a plain arraylist... that is why I asked how to specify the type of p in your system.... I know it is the same for IL but I don't fully understand your system

user Over a year ago

Okay. You have the option to cast the collection in your method of course, but I don't see any reason for not typing it at initialization. I'm on a Mac atm so can't try it, but you could try casting p in the lambda: Where((Person)p => p.gender.Equals("Female"))

|

Community · Accepted Answer · 2017-05-23 12:05:15Z

2

I think something like this should do the trick

using System.Linq;
var females = from Person P in personArrayList where P.Gender == "Female" select P;

[Edit] I had some questions about this myself so asked a question Plain ArrayList Linq c# 2 syntaxes (need a conversion) that can be useful to you.

edited May 23, 2017 at 12:05

CommunityBot

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answered Oct 19, 2013 at 19:26

Napivo

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Comments

Krekkon · Accepted Answer · 2013-10-19 19:15:40Z

0

Do you thank something like that?

protected void btnShowGentle_Click(object sender, EventArgs e)
{
    ListBoxShow.Items.Clear();
    for (int i = 0; i < personArrayList.Count; i++)
    {
        if(personArrayList[i].gender == "Male")
            ListBoxShow.Items.Add(personArrayList[i].ToString());
    }
}

////Possible alternate
//ListBoxShow.Items.Clear();
//ListBoxShow.Items.AddRange(personArrayList.Where( x => x.gender == "Male"));

answered Oct 19, 2013 at 19:15

Krekkon

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