C＃方法更改“图片框”

Question

trying to change an Image in "picturebox". But won't work. no errors,warning.

I have 2 forms, one is a "Message box", and one is a main form. If I try to change the Image from another method (for example: Form1_load) It works.

Form1:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using WindowsFormsApp1;
namespace jatek
{
    public partial class Form1 : Form
         public void Eldontesboss(short adat)
         {
            MessageBox.Show("Number:" + adat); //this is appears,but ...
            box.Image = WindowsFormsApp1.Properties.Resources.alap; //this is not work.
         }
    }
}

Form2:

using jatek;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace WindowsFormsApp1
{
    public partial class Form2 : Form
    {
       private void button1_Click(object sender, EventArgs e)
        {
            Form1 foo = new Form1();
            foo.Eldontesboss(1);
            this.Close();
        }
        private void button2_Click(object sender, EventArgs e)
        {
            Form1 foo = new Form1();
            foo.Eldontesboss(2);
            this.Close();
        }
        private void button3_Click(object sender, EventArgs e)
        {
            Form1 foo = new Form1();
            foo.Eldontesboss(3);
            this.Close();
        }   
    }
}

Change the PictureBox image.

Answer 1

You're creating instances of Form1 that are never displayed; they are simply invisible, in memory. If you want to change the Image in the PictureBox of the CURRENTLY displayed Form1 , then you need a reference to that particular instance. It is unclear from your description which form is the "Main" form and which one is the "Message" form, but I think that Form1 is the main, and Form2 is the message. Furthermore, I'll assume that Form1 is creating an instance of Form2. If that is the case, one way to pass a reference is by setting the Owner property when you call Show() , like this:

// ... in Form1, when Form2 is created ...
Form2 f2 = new Form2();
f2.Show(this); // pass reference to Form1, into Form2

Now, over in Form2, you can cast the Owner property back to type Form1 and work with it:

// ... in Form2, after being displayed with `Show(this)` back in `Form1` ...
private void button1_Click(object sender, EventArgs e)
{
    Form1 foo = (Form1)this.Owner;
    foo.Eldontesboss(1);
    this.Close();
}