Passing DomainUpDown.Value from programmatically generated form to main form

Question

I have a form1 with a showForm button that programmatically creates and opens a new form2 with 4 DomainUpDown elements and a OKBtn button. I need to pass the value of DomainUpDown element using my OKBtn from form2 to form1 richtextbox.My only diffulty is that question mark at the end. Here is the code snippet :

public void showForm_Click(object sender,EventArgs e)
{
       Form frm = new Form();
       frm.Size = new Size(264, 183);
       frm.Name = "MarginSelector";
       frm.Text = "Qiymət ver";
       frm.ShowIcon = false;
       frm.Show();

       DomainUpDown marginRightVal = new DomainUpDown();
       marginRightVal.Location = new Point(150, 100);
       marginRightVal.Size = new Size(42, 40);
       frm.Controls.Add(marginRightVal);
       for (int i = 0; i < 100; i++)
       {
            marginRightVal.Items.Add(i + "%");
       }

       Button OKBtn = new Button();
       OKBtn.Visible = true;
       OKBtn.Text = "OK";
       OKBtn.Size = new Size(30, 23);
       OKBtn.Location = new Point(96, 109);
       frm.Controls.Add(OKBtn);
       OKBtn.Click += new System.EventHandler(this.OKBtn_Click);
}

public void OKBtn_Click(object sender, EventArgs e)
{
       textArea.SelectionLength = 0;
       textArea.SelectedText = string.Filter("margin-top: {0} ; \n, ? ");
}

Answer 1

You can follow Hans Passant his suggestion or you can cast the sender of the click event to a control, get a reference to the form and iterate over the Controls collection to find the control you're looking for. Once found, assign it to a variable and use it in your logic. An implentation could look like this:

public void OKBtn_Click(object sender, EventArgs e)
{
    // assume a Control is the sender
    var ctrl = (Control)sender;
    // on which form is the control?
    var frm = ctrl.FindForm();
    // iterate over all controls
    DomainUpDown domainUpDown = null;
    foreach(var ctr in frm.Controls)
    {
        // check if this is the correct control
        if (ctr is DomainUpDown)
        {
            // store it's reference
            domainUpDown = (DomainUpDown)ctr;
            break;
        }
    }
    // if we have found the control
    if (domainUpDown != null)
    {
        textArea.SelectionLength = 0;
        Debug.WriteLine(domainUpDown.SelectedIndex);
        Debug.WriteLine(domainUpDown.SelectedItem);
        // use the SelectedItem
        textArea.SelectedText = string.Format("margin-top: {0} ; \n,", domainUpDown.SelectedItem );
    }
}

If you have multiple controls on your form you better add an unique name to each of them:

DomainUpDown marginRightVal = new DomainUpDown();
marginRightVal.Location = new Point(150, 100);
marginRightVal.Size = new Size(42, 40);
marginRightVal.Name = "right";
frm.Controls.Add(marginRightVal);

and when you iterate over the control collection you can check for that name:

foreach(var ctr in frm.Controls)
{
    // check if this is the correct control
    if (ctr is DomainUpDown)
    {
        // store it's reference
        domainUpDown = (DomainUpDown)ctr;
        if (domainUpDown.Name == "right")
        {
           // do logic for that value
        }
    }
}

Or you can use the Find method:

var found = frm.Controls.Find("right", false);
if (found.Length>0)
{
    var rightDomain = (DomainUpDown)found[0];
    // do logic here
}