为什么不能在主程序中与表单对象进行交互？

Question

This should be pretty straightforward, yet I am struggling to see any results.

I have the following form code:

//Form1.cs
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 NotepadRW
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        protected TextBox textReadInfo;
        public void SetReadInfo(String str)
        {
            txtReadInfo.Text = str;
        }
    }
}

I also have the following program code:

//Program.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace NotepadRW
{
    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Form1 form1 = new Form1();
            Application.Run(form1);

            form1.SetReadInfo("Hi");

        }
    }
}

Which result in the following form:

Why is it not displaying the string I provide it? Am I not properly understanding how the program works with a windows form? Does execution of the Main() method of Program.cs stop when the new instance of Form1 is called?

Note: I've tried this with a text box and a rich text box. Same results.

Extra points: Am I following encapsulation correctly? I was going to modify the text box to be publicly accessible (which will work), but I thought this would be the "correct" way to do it.

Answer 1

While it is not obvious from the documentation , the Application.Run(Form) method blocks. You can infer this from the following quote:

The Dispose method of the Form class will be called prior to the return of this method.

This means that the form will do its thing and it has to be done doing its thing before Run will return. Ie, it blocks.

You can accomplish what you want by switching up the order though. Instead of

Form1 form1 = new Form1();
Application.Run(form1);
form1.SetReadInfo("Hi");

try

Form1 form1 = new Form1();
form1.SetReadInfo("Hi");
Application.Run(form1);

Answer 2

You shouldn't be making your text box public, otherwise you may get cross thread execution exception.

The reason your code is not working is because you are running the form on the main thread, so anything after Application.Run() does not get executed. You can run your form on a separate thread.

Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Form1 form = new Form1();

            System.Threading.Thread workerThread = new System.Threading.Thread(() => Application.Run(form));

            workerThread.Start();

            form.SetReadInfo("Hello");