c# using checkbox from form2 in form1

I would do something like this:

Since Form1 creates Form2, and Form1 needs to manipulate Form2 then you can change this from Form2.Designer.cs:

private System.Windows.Forms.Checkbox cbTESTING;

To:

public System.Windows.Forms.Checkbox cbTESTING;

Assuming in Form1 you created Form2 like this:

Form2 f2 = Form2();
f2.Show();

Then you use this to check cbTESTING:

if(f2.cbTESTING.Checked) // do stuff  ;

EDIT: I have seen your comment which says they do not relate to each other at all which makes it impossible to achieve in any easy method. What you said implies communication between these two THREADS since each Form runs in a Thread and these threads are unrelated. Communication is NOT an easy thing to do, you can try it using UDP and Events but trust me, having a direct relation between them would make things MUCH easier for you.

Anyway, I would assume some other Form or Thread would launch these Forms?

Here's a pretty clean way to fix this.. just change the access modifier to public for cbTESTING in the designer for Form2.

That is, in Form2.Designer.cs, change

private System.Windows.Forms.Checkbox cbTESTING;

to

public System.Windows.Forms.Checkbox cbTESTING;

Then, Form1 can look like this:

public partial class Form1 : Form
{
    public Form1() {
        InitalizeComponent();

        Form2 secondForm = new Form2();
        bool isChecked = secondForm.cbTESTING.checked;
    }
}

Edits: removed protected solution, which isn't a great option in this case.

Here you have a ugly way to do what you want:

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

    private void button1_Click(object sender, EventArgs e)
    {
        var frm = new Form2();
        frm.ShowDialog();

        label1.Text = frm.TextBoxChecked;
    }
}

//Just declare a prop into Form2 a set it with the value you need
public partial class Form2 : Form
{
    public string TextBoxChecked { get; set; }
    public Form2()
    {
        InitializeComponent();
    }

    private void checkBox1_CheckedChanged(object sender, EventArgs e)
    {
        if (checkBox1.Checked)
            TextBoxChecked = "Checkbox_1_checked";
        else
            TextBoxChecked = "Checkbox_1_unchecked";
    }
}

Lets do things in a cool way. Maybe a good aproache is to say to Form2: "Hey you, when your checkbox change let me know", It sounds like a callback. So let do it:

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

    private void doWhenCheckBoxChange(string text)
    {
        //I'm receiving the notification indicating that the checkbox has changed
        label1.Text = text;
    }

    private void button1_Click(object sender, EventArgs e)
    {
        var frm = new Form2();
        //I'm passing a callback to Form2, Here is where I say 
        //"Hey you, let me know where your checkbox change"
        frm.DoWhenCheckboxChange = doWhenCheckBoxChange;
        frm.ShowDialog();

        //label1.Text = frm.TextBoxChecked;
    }
}

public partial class Form2 : Form
{
    //public string TextBoxChecked { get; set; }
    public Action<string> DoWhenCheckboxChange;
    public Form2()
    {
        InitializeComponent();
    }

    private void checkBox1_CheckedChanged(object sender, EventArgs e)
    {
        //TextBoxChecked = "Checkbox_1";
        //Notify to Form1 that checkbox has changed.
        if (checkBox1.Checked)
            DoWhenCheckboxChange("Checkbox_1_checked");
        else
            DoWhenCheckboxChange("Checkbox_1_unchecked");
    }
}

If you test the second aproache, you will discover that you dont need to close your Form2 to see the changes.

Might not be the most elegant solution but will definitely work. Declare a public static bool variable in Form2. Add Checkbox changed event to your checkboxes and change those static variables accordingly. Then just check those variable in Form1 such as Form2.VariableName let me know if you need further explanation

Edit

In Form2 declare public static bool CheckBoxStatus = false; false by default, you can change that.

Also in Form2 add following event checkBox1.CheckedChanged += new EventHandler(CheckedChanged) and add appropriate function such as

private void CheckedChanged(object sender, EventArgs e)
{
    CheckBoxStatus = checkBox1.Checked;
}

And Finally in Form1 one you can simply check if that checkbox is checked like this

if(Form2.CheckBoxStatus == true) ;
else ;

Hope that helps. *PS sorry my formatting, new to posting answers here.