Q:

How can i give a focus to a listBox in the constructor and when a new item was added?

In the constructor i did:
if (listBox1.Items != null)
            {
                listBox1.Focus();
            }

But when im running the program i cant move with the keyboards up down in listBox since the focus is on a button somewhere else in the Form. I need to click with the mouse on the listBox to get the focus.
Another problem i want that when the user add a new item to the listBox the focus will be automatic on the last added item. For this problem this is the code where im adding a new item to the listBox:
private void KeysValuesUpdate()
        {
            using (var w = new StreamWriter(keywords_path_file))
            {
                crawlLocaly1 = new CrawlLocaly();
                crawlLocaly1.StartPosition = FormStartPosition.CenterParent;
                DialogResult dr = crawlLocaly1.ShowDialog(this);
                if (dr == DialogResult.OK)
                {
                    if (LocalyKeyWords.ContainsKey(mainUrl))
                    {
                        LocalyKeyWords[mainUrl].Clear();
                        LocalyKeyWords[mainUrl].Add(crawlLocaly1.getText());
                    }
                    else
                    {
                        LocalyKeyWords[mainUrl] = new List<string>();
                        LocalyKeyWords[mainUrl].Add(crawlLocaly1.getText());
                    }
                    Write(w);
                    ClearListBox();
                }
                if (dr == DialogResult.Cancel)
                {
                    Write(w);
                }
            }
        }

        private void ClearListBox()
        {
            data.Clear();
            listBox1.DataSource = null;
            string sb;
            foreach (KeyValuePair<string, List<string>> kvp in LocalyKeyWords)
            {
                for (int i = 0; i < kvp.Value.Count(); i++)
                {
                    sb = "Url: " + kvp.Key + " --- " + "Local KeyWord: " + kvp.Value[i] + Environment.NewLine;
                    data.Add(sb.ToString());
                }
            }
            listBox1.DataSource = data;
        }

The question is why i cant set the focus in any of the cases on the listBox items ?
In the first case in the constructor the focus i want it to be on the last item in the list and also each time im adding a new item so the focus will be on the last added item.

A:

Most likely, the item is being selected, you just can't tell because a different control has the focus. There are a couple of different ways that you can solve this, depending on the design of your application.

For the first part of the question, you should set the Focus in the Page/Form Load event, since at the constructor level controls are under initialization process.
Set the focus to the ListView first whenever your form is displayed. The user typically sets focus to controls by clicking on them. However, you can also specify which controls gets the focus programmatically. One way of doing this is by setting the tab index of the control to 0 (the lowest value indicates the control that will have the initial focus). A second possibility is to use the following line of code in your form's Load event, or immediately after you set the Selected property:
listBox1.Select();

The problem with this solution is that the selected item will no longer appear highlighted when the user sets focus to a different control on your form (such as a textbox or a button).
For the second part of the question, selecting last added item in the ListBox, use the following code:
listBox1.SelectedIndex = listBox1.Items.Count - 1;
listBox1.SetFocus();

