更新ListView上的SelectedItem

Question

I have a ListView that displays multiple rows of ListViewItems. The user is able to edit the row by clicking the edit button which opens up another form displaying the selected row and the data within it. The problem I am having is that I cannot seem to update the ListViewItem on the parent form when I press the update button. The code I am using keeps throwing the exception message "An unhandled exception of type 'System.NullReferenceException' occurred in ToDoList.exe". I have tried different approaches to updating the selected item but cannot seem to get a working code.

This is the code I am using on the form that displays the selected row, button1 is the "Update Row" button that should update the listView.

private void button1_Click(object sender, EventArgs e)
    {
        Form1 form1 = (Form1)this.Owner;

        int i = 0;
        ListViewItem item = form1.listView1.SelectedItems[i];
        textBox1.Text = item.SubItems[0].Text;
        richTextBox1.Text = item.SubItems[1].Text;
        comboBox1.Text = item.SubItems[2].Text;
        dateTimePicker1.Text = item.SubItems[3].Text;

        this.Close();
    }

Answer 1

To make a form owned by another form, assign its Owner property a reference to the form that will be the owner.

https://msdn.microsoft.com/en-us/library/system.windows.forms.form.owner%28v=vs.110%29.aspx

You need to set the Owner property first

Answer 2

Finally managed to fix the problem. There were two issues with my code. One was with the way I was opening up the child Form3 and not referring to Form1 as a class and the other was with the code I was using to edit a row not functioning correctly.

Changed it to this and came to the solution;

Form1 code - method of opening Form3 with the data from the selected row, originally used the code:

private void button2_Click(object sender, EventArgs e)
    {
        if (listView1.SelectedItems.Count == 0) return;

        Form3 form3 = new Form3();

        int i = 0;
        ListViewItem item = listView1.SelectedItems[i];
        string title = item.SubItems[0].Text;
        string description = item.SubItems[1].Text;
        string priority = item.SubItems[2].Text;
        string datedue = item.SubItems[3].Text;
        form3.textBox1.Text = title.ToString();
        form3.richTextBox1.Text = description.ToString();
        form3.comboBox1.Text = priority.ToString();
        form3.dateTimePicker1.Text = datedue.ToString();

        form3.Show();  
    }

But changed it to this:

private void button2_Click(object sender, EventArgs e)
    {
        if (listView1.SelectedItems.Count == 0) return;

        using (Form3 form3 = new Form3())
        {
            int i = 0;
            ListViewItem item = listView1.SelectedItems[i];
            string title = item.SubItems[0].Text;
            string description = item.SubItems[1].Text;
            string priority = item.SubItems[2].Text;
            string datedue = item.SubItems[3].Text;
            form3.textBox1.Text = title.ToString();
            form3.richTextBox1.Text = description.ToString();
            form3.comboBox1.Text = priority.ToString();
            form3.dateTimePicker1.Text = datedue.ToString();

            form3.ShowDialog(this);
        }
    }

And finally changed the code in Form3 to this:

private void button1_Click(object sender, EventArgs e)
    {
        Form1 form1 = (Form1)this.Owner;

        int i = 0;
        ListViewItem item = form1.listView1.SelectedItems[i];
        item.SubItems[0].Text = textBox1.Text;
        item.SubItems[1].Text = richTextBox1.Text;
        item.SubItems[2].Text = comboBox1.Text;
        item.SubItems[3].Text = dateTimePicker1.Text;

        this.Close();
    }