You can use the ComboBox.SelectedText property to retrieve or change the currently selected text in a System.Windows.Forms.ComboBox control. However, you should be aware that the selection can change automatically because of user interaction. For example, if you retrieve the ComboBox.SelectedText value in a button Control.Click event handler, the value will be an empty string. This is because the selection is automatically cleared when the input focus moves from the combo box to the button.

When the combo box loses focus, the selection point moves to the beginning of the text and any selected text becomes unselected. In this case, getting the ComboBox.SelectedText property retrieves an empty string, and setting the ComboBox.SelectedText property adds the specified value to the beginning of the text.

When the combo box gains focus, the full text in the control is automatically selected. If you call the control's Control.Focus method to set the input focus, the full text is selected regardless of whether the control already had focus.

When the user selects an item from the drop-down list or by using the UP ARROW and DOWN ARROW keys, the text for the new item is automatically selected. However, if you try to get the ComboBox.SelectedText value in a ComboBox.SelectedIndexChanged or ListControl.SelectedValueChanged event handler, the property returns an empty string. This is because, at the time of these events, the previous ComboBox.SelectedText value has been cleared and the new value has not yet been set. To retrieve the current value in a ComboBox.SelectedIndexChanged or ListControl.SelectedValueChanged event handler, use the ComboBox.SelectedItem property instead.