How to stop passing value from one form to other in formclosing event?

Question

I got 2 forms (form1, form2). I can pass values from form2 to form1, but the main problem is, when I just close the form2, he will pass the values anyway, so I got empty values in form1. For example: I add a value of 2000 euros to form 1 textbox&label, and then when I open one more time the form2, and leave the texbox clear and radiobutt unchecked,then close the form2 with the red X closing button, the form1 values of 2000 euros will disappear. Here's the source code of the passing values and buttons:

FORM2

private string pss;
public string Passvalue
{  

    get { return pss; }
    set { pss = value; }
}
private string pss2;  
public string Passvalue2
{
    get { return pss2; }
    set { pss2 = value; }
}

public void Btn1_Click(object sender, EventArgs e)//The passvalue button
{
    string eur="EUR";
    Passvalue = ukupnaCifraTB.Text;//textbox form2=the number sender
    ukupnaCifraTB.Text = String.Empty;



    if (radioButton1.Checked)
    {
        radioButton1.Text = eur;
        Passvalue2 = radioButton2.Text;
    }

    this.Close();
}

Here's form1:

private string backvalue;
public string BackedValue
{
    get { return backvalue; }
    set { backvalue = value; }           
}

private string backedText;
public string BackedText
{
    get { return backedText; }
    set { backedText =  value; }
}

public void Btn1_Click(object sender, EventArgs e)
{
    Form2 f2 = new Form2(); 
    f2.ShowDialog();
    trenutnoStanjeTB.Text = f2.Passvalue;//trenutnostanjeTB=textbox(form1)=gets number from form2
    DinEuLab1.Text = f2.Passvalue2;//dineulab1=label form1=gets the eur text
    DinEuLab2.Text = f2.Passvalue2;

}

What I need to change/add to resolve my problem? I want that when I once pass the values, and then open the form2 and close it, to not send the empty values to form1.

Answer 1

a simple query for emptiness could resolve your issue. At the point where your Form2 is closed and you try to assign the Passvalues to the Textboxes of Form1, just check whether there are valid values in f2.Passvalue and f2.Passvalue2. If they are not empty assign them, otherwise let the old value remain

trenutnoStanjeTB.Text = !String.IsNullOrWhiteSpace(f2.Passvalue) ? f2.Passvalue : trenutnoStanjeTB.Text;

DinEuLab1.Text = !String.IsNullOrWhiteSpace(f2.Passvalue2) ? f2.Passvalue2 : DinEuLab1.Text;

and so on