ComboBox control is one of the most useful control in Windows Forms. It provides an interface to display the list of items, and allows to select the items. To save the space on Windows Form, it lists the items as a drop-down list. That means, initially the control displays a text box & a button. When click on the button, it displays the list of items and the selected item will be displayed in a text box.
ComboBox control is a combination of text box, button & list box controls.
We need to add the entries to
ComboBox control, in order to display them when needed. As mentioned above,
ComboBox control displays it’s items in a list box. It holds the list of items in it’s
Items collection, which is an important property of this control. That said,
Items property is of collection type. To add or remove the items to & from the
ComboBox control (see below Methods section), we use this
Sorted property is set to True , it’s items will be sorted.
DropDownStyle property controls the appearance and functionality of the
ComboBox control. Depending on your program requirement, you can set this property to proper value. When set this property to;
Simple, it will display it’s items in the list box and a text box will be displayed to display the selected item from it’s list box. Text box is allowed to edit the text it displays.
DropDown, it displays a text box and a button control next to it. When click on the button control, it shows the list of items the control has and allows to select the item(s). The selected item will be displayed in the text box and it is editable.
DropDownList, it behaves like when we set this property to
DropDown; except, the text box is NOT editable. That means, when we select the item from the
ComboxBox control, it displays the selected item in the text box and NOT allowed to edit the text.
Another useful property is,
MaxDropDownItems property. This allows to set the number of items to be visible at a time, when drop-down list is displayed. This you set to the proper value, depending on your application window size.
ComboBox control has the index values. When we select an item from the control, the
SelectedIndex value will be updated with the selected item’s index value. This is very useful property to identify which item is selected in the
Adding and removing items to & from the
ComboBox control can be done through the methods of
Items.Add method will add an item to the
ComboBox control. And,
Items.Remove method will be used to remove an item from the
To remove all items from the
ComboBox control, we can use
SelectedIndexChanged event will be triggered whenever we select an item from the
ComboBox control. Actually this will be triggered whenever
SelectedIndex property value is changed.
DropDown event will be raised when the drop-down portion of the
ComboBox control is visible. Usually this will be visible when we click on the button to select an item from the
ComboBox control. Once the selection is done, the drop-down portion will be hidden. Then,
DropDownClosed event will be triggered. These two events are very useful to place the code to update or reset the changes for the