How to return a value from a Form in C#?

Question

I have a main form (let's call it frmHireQuote) that is a child of a main MDI form (frmMainMDI), that shows another form (frmImportContact) via ShowDialog() when a button is clicked.

When the user clicks the 'OK' on frmImportContact, I want to pass a few string variables back to some text boxes on frmHireQuote.

Note that there could be multiple instances of frmHireQuote, it's obviously important that I get back to the instance that called this instance of frmImportContact.

What's the best method of doing this?

Answer 1

Create some public Properties on your sub-form like so

public string ReturnValue1 {get;set;} 
public string ReturnValue2 {get;set;}

then set this inside your sub-form ok button click handler

private void btnOk_Click(object sender,EventArgs e)
{
    this.ReturnValue1 = "Something";
    this.ReturnValue2 = DateTime.Now.ToString(); //example
    this.DialogResult = DialogResult.OK;
    this.Close();
}

Then in your frmHireQuote form, when you open the sub-form

using (var form = new frmImportContact())
{
    var result = form.ShowDialog();
    if (result == DialogResult.OK)
    {
        string val = form.ReturnValue1;            //values preserved after close
        string dateString = form.ReturnValue2;
        //Do something here with these values

        //for example
        this.txtSomething.Text = val;
    }
}

Additionaly if you wish to cancel out of the sub-form you can just add a button to the form and set its DialogResult to Cancel and you can also set the CancelButton property of the form to said button - this will enable the escape key to cancel out of the form.