How to pass data from another form and back

Question

I've been trying to get this working. I'm sure I've written in correctely

Form 1

private string _temp;
public string Temp
{
    get { return _temp; }
    set { _temp = value; }
}
private void button1_Click(object sender, EventArgs e)
{
    _temp = "test";
}

Form 2

private void button1_Click(object sender, EventArgs e)
{
    Form1 main = new Form1();
    MessageBox.Show(main.Temp);
}

What's the problem? You haven't described any issues with this code. — ryanyuyu, Feb 04 '15 at 19:27
possible duplicate of [Communicate between two windows forms](http://stackoverflow.com/questions/1665533/) — Dour High Arch, Feb 04 '15 at 19:29
I tried checking if there are any values for "main.Temp" but it just said it's null — Alfie McNarutoad, Feb 04 '15 at 19:29
you create a new instance of the form and then pull the value from the property - by default, it is null.This is expected. Why are you creating an instance of the form? Why not hold it in a global private variable and access it to then have the same instance you are pulling the data for or pass the variable value to the next form? — Ahmed ilyas, Feb 04 '15 at 19:30
Yeah, and until you click Form1 main's button (and trigger that event handler), `main.temp` will be a default null. — ryanyuyu, Feb 04 '15 at 19:32
[C# Basics Tutorial - Encapsulation](http://www.tutorialspoint.com/csharp/csharp_encapsulation.htm) I'd suggest reading and understanding the difference especially between `private && public` — MethodMan, Feb 04 '15 at 19:38

score 0 · Accepted Answer · answered Feb 04 '15 at 19:33

You have to get the reference to the Form1 instance via the sender parameter (assuming that Form2's button1_Click handler is attached to a button on Form1):

//Form2
private void button1_Click(object sender, EventArgs e)
{
    Button button = (Button) sender;
    Form1 main = (Form1) button.FindForm();
    MessageBox.Show(main.Temp);
}

How to pass data from another form and back

1 Answers1