title: Popup window in winforms
body: <p>I have a windows form application where I show information about products and product categories in a datagridview. I would like to create a popup window so when I right click on a product and choose add to category a popup window appears and in that I show all the categories in a dropdownbox and when I click a button the product add to the category. </p>
  
  <p>I want to create a popup window with a dropdownbox and a button. How do I do that in a window form application?</p>