c# Changing Textbox.Text from different class

**Mastermosley** · 03-09-2009

I have the function AddToText which is located in the Form1 Partial Class

Code:

public void AddToText(string text)
{
this.txtStatus.Text = this.txtStatus.Text + "\r\n";
}

I want to call this from a different class so I do:

Code:

Form1 frm = new Form1();
frm.AddToText("Test");

I click a button called start and it calls the procedure on a different class and runs the code above. But nothing appears in my textbox. It works when I call it from the Partial Class Though.

WTF?

**Rare177** · 03-09-2009

hmmm maybe you should look over your AddToText function again, i dont see where you're using that text paramater.

**Mastermosley** · 03-09-2009

oh my bad, Its in there on my actually code though and its not working. I read something about Form1 frm = new Form1(); creates a new form and the old one isnt motified or something, dunno if that is relevant.

**Mastermosley** · 03-09-2009

Also I just added a MessageBox.Show(txtStatus.Text);

and it displayed my status so something is in the textbox, but I cant see it...

**Mastermosley** · 03-09-2009

Okay so I figured it out. I typed frm.Show() after I initiate Form1 frm = new Form1 how do I do that, like make reference to the form without actually creating a new one??

**Rare177** · 03-09-2009

sounds like you're referring to the wrong instance of form1, if you're using vc# 2005-2008 you will see the program starts the form like this..

Code:

        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }

you need to referrence to that form1, one way of doing this which isn't the best idea but will be suitable for your case, is by creating a static object for the form within the Program class by doing this.

Code:

        static Form1 mainForm;
        [STAThread]
        static void Main()
        {
            
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            
            mainForm = new Form1();

            Application.Run(mainForm);
            
        }

then you can change your textbox by going Program.mainForm.textBox.Text = "something";

**prog-bman** · 03-09-2009

You will need to pass it in to the form or class you want to modify it in.

Code:

//In a class or another form besides Form1
public Form1 Opener
{
    set{this.mOpener = value;}
}

**Mastermosley** · 03-10-2009

Originally Posted by prog-bman

You will need to pass it in to the form or class you want to modify it in.

Code:

//In a class or another form besides Form1
public Form1 Opener
{
    set{this.mOpener = value;}
}

I dont understand that. I tried the post above but mainForm doesn't show up when I type Program.________ it should appear there but it doesn't.

**Mastermosley** · 03-10-2009

Nevermind I got it, I had to add a public beside the static Main();. Also What is the downside of doing this? as you stated above you said its not the best idea.

**Rare177** · 03-10-2009

It's just not good practice to make objects static, but it's about all you can do in this case.

**prog-bman** · 03-10-2009

Form1 has a button that opens Form2

Code:

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

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

        private void button1_Click(object sender, EventArgs e)
        {
            //
            //Create the second form and set the opener to this instance.
            //
            Form2 mySecondForm = new Form2();
            mySecondForm.Opener = this;

            mySecondForm.Show();
        }

        public void SetText(string customText)
        {
            this.textBox1.Text = customText;
        }
    }
}

Form2 has a button that sets Form1's text field

Code:

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

namespace ExampleFormOpener
{
    public partial class Form2 : Form
    {
        private Form1 mOpener = null;

        public Form2()
        {
            InitializeComponent();
        }

        public Form1 Opener
        {
            set { this.mOpener = value; }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (this.mOpener != null)
            {
                this.mOpener.SetText("Text set from another form!");
            }//if
        }
    }
}

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