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Accepted
Javier
Asked: 2020-12-24 09:02:09 +0800 CST 2020-12-24 09:02:09 +0800 CST

ArrayList of c# objects

  • 772

I have an ArrayList of objects of a class but I don't know how to access the information of the ArrayList.

class Personas
{
    string nombres ="";
    string apellidos ="";

    public Personas(string nombres,string apellidos)
    {
        this.nombres = nombres;
        this.apellidos = apellidos;

    }
}

private void button3_Click(object sender, EventArgs e)
{
      Personas personas;
      ArrayList lista;

      Personas personas = new Personas("BYRON","RAMIREZ");
      lista = new ArrayList();
      lista.Add(personas);

      MessageBox.Show(personas[0]["nombre"]);
}

I get an error when displaying the information.

c#

2 Answers

  1. One option is to overwrite the method ToString():

    class Personas
{
    string nombres = "";
    string apellidos = "";

    public Personas(string nombres, string apellidos)
    {
        this.nombres = nombres;
        this.apellidos = apellidos;

    }

    public override string ToString()
    {
        return "Persona: " + nombres + " " + apellidos;
    }

}

    this way you could print the value of the object:

    private void button3_Click(object sender, EventArgs e)
    {
    Personas personas;
    ArrayList lista;

    personas = new Personas("BYRON", "RAMIREZ");
    lista = new ArrayList();
    lista.Add(personas);

    MessageBox.Show(lista[0].ToString());
}

    enter image description here

    Another option is to add the modifiers publicto your object's properties:

    class Personas
    {
       public string nombres = "";
        public string apellidos = "";

        public Personas(string nombres, string apellidos)
        {
            this.nombres = nombres;
            this.apellidos = apellidos;

        }

    }

    This way you could read the properties:

        private void btnDelete_Click(object sender, EventArgs e)
    {

        Personas personas;
        ArrayList lista;

        personas = new Personas("BYRON", "RAMIREZ");
        lista = new ArrayList();
        lista.Add(personas);

        Personas persona = (Personas)lista[0];
        MessageBox.Show("Persona: " + persona.nombres + " " + persona.apellidos);

    }

    enter image description here

    • 1
  2. Best Answer

    There are several things wrong and to take into account in your code:

    Of the classPersonas

    It is not a good practice to name a class that is not a collection in plural, the same for the fields, they must also be public or you will not be able to access them outside the class. Modify it to something like this:

    class Persona
{
    public string nombre ="";
    public string apellido = "";

    public Persona(string nombre, string apellido)
    {
        this.nombre = nombres;
        this.apellido = apellidos;
    }
}

    The ArrayList gives you an error because when you access element 0 of its position, it returns the object of that position, that is, a Person element, in order to correctly access the name field that you indicate, you must do the following:

     Persona p = (Persona)lista[0];

 MessageBox.Show(p.nombre);
    • 1