How to refresh ComboBox Values from database in Windows Forms Application

I do have combo box on my page where the items are retrieved from database.

I have an link label which leads to new form to add value for corresponding column in database.

After add the value, when i click refresh on my current page, the values in combo box must be updated. 

 I have used this

 private void button3_Click(object sender, EventArgs e)
        {
            this.Refresh();
        }