如何从另一个类在Form1中创建对象？

Question

I am trying to write program with C# to dynamicaly create PictureBox'es from another class.

Here what is done:

In class Form1 creating object of another class and call procedure in that class which creates objects(many PictureBox'es) I want

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Lines_online
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            //trying to draw NxM table 
            //where N is horizontal cell count M is vertical cell count
            Table tbl = new Table();
            tbl.Tablenm(9, 9);
        }
    }
}

The class Table code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Windows.Forms;

namespace Lines_online
{
   public class Table : Form1
    {
        List<PictureBox> cell = new List<PictureBox>(); 
        public void Tablenm(int n, int m)
        {
            for (int i = 0; i < n*m; i++)
            {
                PictureBox pict = new PictureBox();
                cell.Add(pict);
                cell[i].Size = new Size(20, 20);
                cell[i].Location = new Point(30 + (i % n) * 19, 30 + (i / m) * 19);
                cell[i].Image = Properties.Resources.lang20x20;
                Controls.Add(cell[i]);
            }
        }
    }
}

Then code is executed it does nothing and gives no errors (I think it creates the objects somethere, but definetaly not in Form1 window). If procedure in the class Table moved to Form1 class it works perfectly, but I want to control it from other class to reduce code size in Form1. I tried to create Form1 object in Class Table:

Form1 frm1 = new Form1();

It did not help. What I am doing wrong, or maybe using bad approach to this problam?

Answer 1

Note: in your code you are inheriting table from Form1. This does mean that Table represents a new form, instead of a reference to the current existing form, and therefore it doesn't do anything.

In the Controls property of your original form, you are just adding another form, which definitely isn't the behaviour that you need.

I've tooked your code as a start and adapted it a bit. I do think that this should work.

Create your class Table, but DON'T inherit from Form1. Make your class that it looks like the following:

public class Table
{
    public List<PictureBox> Render(int n, int m)
    {
        List<PictureBox> returnList = new List<PictureBox>();

        for (int i = 0; i < n*m; i++)
        {
            PictureBox pict = new PictureBox();

            pict.Size = new Size(20, 20);
            pict.Location = new Point(30 + (i % n) * 19, 30 + (i / m) * 19);
            pict.Image = Properties.Resources.lang20x20;

            returnList.Add(pict);
        }

        return returnList;
    }
}

Then, in your main form, you can call your method:

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        var table = new Table();
        IEnumerable<Control> controls = table.Render(10, 10);

        foreach (var control in controls)
        { this.Controls.Add(control); }
    }
}

I believe that should work, but I haven't tested it. Also note that this code is not optimized. You should have parameters passed to the function in order to make it more generic.

Answer 2

You can return the List<PictureBox> to Form1

 public List<PictureBox> Tablenm(int n, int m)
 {
        for (int i = 0; i < n*m; i++)
        {
            PictureBox pict = new PictureBox();
            cell.Add(pict);
            cell[i].Size = new Size(20, 20);
            cell[i].Location = new Point(30 + (i % n) * 19, 30 + (i / m) * 19);
            cell[i].Image = Properties.Resources.lang20x20;
        }

        return cell;
 }

Then add it inside you form:

 private void Form1_Load(object sender, EventArgs e)
 {
        //trying to draw NxM table 
        //where N is horizontal cell count M is vertical cell count
        Table tbl = new Table();
        var pictureBoxes = tbl.Tablenm(9, 9)
        foreach (var pictureBox in pictureBoxes)
        {
          Controls.Add(picturebox)}
        }
 }

Answer 3

//You need to add picturebox control to form1 control in loop, //Form1.Control.Add(cell[i]);

//-------------------

public void Tablenm(int n, int m, Form Form1)
        {
            for (int i = 0; i < n*m; i++)
            {
                PictureBox pict = new PictureBox();
                cell.Add(pict);
                cell[i].Size = new Size(20, 20);
                cell[i].Location = new Point(30 + (i % n) * 19, 30 + (i / m) * 19);
                cell[i].Image = Properties.Resources.lang20x20;                
                Form1.Control.Add(cell[i]);
            }
        }