从另一个类C＃访问表单的控件

Question

I'm a newbie in c# and visual studio, but not programming in general. I searched for answer to my question for 3 days and I found plenty of them, but for some weird reason (I'm sure I'm missing something very obvious) I cannot get it to work. I think it's the most basic question newbies like me ask. I have a form (Form3) with a text box and a button (I set it up is just for testing purposes). I want to populate and read this text box from another class. I understand the most proper way to do this is to create a property in Form3.cs with GET and SET accessors. I did that but I cannot get it to work. I'm not getting any error messages, but I'm not able to set the value of the text box either. It just remains blank. Here's my sample code:

namespace WindowsFormsApplication1
{
    public partial class Form3 : Form
    {
        public string setCodes
        {
            get { return test1.Text; }
            set { test1.Text = value; }
        }

        public Form3()
        {
            InitializeComponent();
        }

        private void Form3_Load(object sender, EventArgs e)
        {   }

        private void button1_Click(object sender, EventArgs e)
        {
            a.b();
        }
    }

    public class a
    {       
        public static void b()
        {
            Form3 v = new Form3();
            v.setCodes = "abc123";
        }
    }
}

Can someone lend me a hand solving this?

Answer 1

The problem is you are setting the value to a new instance of the form. Try something like this:

public partial class Form3 : Form {
    public string setCodes
    {
        get { return test1.Text; }
        set { test1.Text = value; }
    }

    private A a;

    public Form3()
    {
        InitializeComponent();
        a = new A(this);
    } 

    private void button1_Click(object sender, EventArgs e)
    {            
        a.b();            
    }


    private void Form3_Load(object sender, EventArgs e)
    {

    }
}

public class A
{       
    private Form3 v;

    public a(Form3 v)
    {
        this.v = v;
    }

    public void b()
    {
        v.setCodes = "abc123";
    }
}    

Answer 2

You're creating a brand new Form3() instance.
This does not affect the existing form.

You need to pass the form as a parameter to the method.

Answer 3

Try this:

public partial class Form3 : Form
{
    /* Code from question unchanged until `button1_Click` */

    private void button1_Click(object sender, EventArgs e)
    {
        a.b(this);
    }
}

public class a
{       
    public static void b(Form3 form3)
    {
        form3.setCodes = "abc123";
    }
}

This passes the current instance of the form to the other class so that it can update the setCodes property. Previously you were creating a new form instance rather than updating the current form.

Answer 4

Sending form instance to other other class

Form1 objForm1=new Form1();
obj.Validate(objForm1);

Easy way to access controls in another class by modifying Controls Private to Public in the Form(Designer.cs)