Add combobox item from another form won't work

Question

I want to add an item to my combobox in form1 from form2. But if I press the button, form2 closes but the item is not added in form1. I hope you can help me! I found no solution for this problem in the internet.

Form 2:

public void button5_Click(object sender, EventArgs e)
{
    Form1 main = new Form1();

    main.AddItem("Item");
    this.Close();
}

Form 1:

public void AddItem(object item)
{
    comboBox1.Items.Add(item);
}

It's because you create new form and then destroy it. You must have reference to form1 instance, instead of creating new one. — Spawn, Sep 24 '15 at 14:03
http://stackoverflow.com/questions/1736444/using-the-controls-of-one-form-into-another?lq=1 — ElectricRouge, Sep 24 '15 at 14:05

score 0 · Answer 1 · answered Sep 24 '15 at 14:10

0

Reference the name property of your 'Form1' don't create a new instance. Then reference that forms combobox control.

Your original code creates a NEW instance. Meaning its creating a new version of Form1 and not accessing the original!

The code below should help

  public void button5_Click(object sender, EventArgs e)
        {

          Form1 myForm = whateverYourFormsNamePropertyIs;
          myForm.Combobox.AddItem("Item");
          this.Close();

        }

answered Sep 24 '15 at 14:10

Harvey

1,320
3
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I tried it but I get this Error: (translated from german) Error 7 "Launcher.Form1" is a "type", but its used a a variable. I used: Form1 myForm = Form1; – AlGrande Sep 24 '15 at 14:55
http://stackoverflow.com/questions/7273862/c-sharp-how-to-make-two-forms-reference-each-other Here is a good example of how to reference other forms within your application. You'll need to pass the reference into Form2 on construction – Harvey Sep 24 '15 at 14:57
Fix your answer; don't post yet another link. – B. Shea Oct 06 '16 at 18:34

Umut D. · Accepted Answer · 2015-09-25T14:24:50.123

0

First of all: You have to change comboBox access modifier to public. Then:

Form 2:

public void button5_Click(object sender, EventArgs e)
{
     Form1 main = new Form1();
     main.AddItem("Item");

     this.Hide(); // This will hide Form2 ("this." is redundant)
     main.ShowDialog(); // This will show Form1
}

edited Sep 25 '15 at 14:24

answered Sep 24 '15 at 18:51

Umut D.

1,746
23
24

Thank You! This works! But if I click the button, form1 is opened 2 times. How can I close the first form1 if I click the where and the second form1 opens? – AlGrande Sep 25 '15 at 09:31
You can remove "main.ShowDialog()". – Umut D. Sep 25 '15 at 14:48

score 0 · Answer 3 · answered Jun 01 '16 at 15:25

In form2...

    Form1 f;
    public Form2(Form1 parent)
    {
        InitializeComponent();
        f = parent;
    }
    private void Add_Click(object sender, EventArgs e)
    {
        f.comboBox1.Items.Add("item");
    }

In form1

public void AddItem(object item)
{
  comboBox1.Items.Add(item);
  Form2 f = new Form2(this);
  f.Show();
}

score 0 · Answer 4 · answered Dec 11 '19 at 11:10

orginal form

private void FormPeople_Load(object sender, EventArgs e)
    {
        populateComboBoxTitles();
}
public void populateComboBoxTitles()
        {
            comboBox2.Items.Clear();
            comboBox2.Items.Add("mr");
             comboBox2.Items.Add("miss");

}
private void button5_Click(object sender, EventArgs e)
    {
FormAddTitle formAddTitle = new FormAddTitle(this);
        formAddTitle.Show();
}

secondary form

 FormPeople formPeople;
    public FormAddTitle(FormPeople formPeople)
    {
        InitializeComponent();
        this.formPeople = formPeople;
    }
private void button1_Click(object sender, EventArgs e)
    {
if (formPeople != null)
            formPeople.populateComboBoxTitles();
}

Add combobox item from another form won't work

4 Answers4