You can use this property to determine whether any characters are currently selected in the combo box control before performing operations on the selected text. When the value of the ComboBox.SelectionLength property is set to a value that is larger than the number of characters within the text of the control, the value of the ComboBox.SelectionLength property is set to the entire length of text within the control minus the value of the ComboBox.SelectionStart property (if any value is specified for the ComboBox.SelectionStart property).