C＃：使用ListView.SelectedItems [0]后选择不同项目的问题

I have a problem, I am using the method in listview ListView.SelectedItems[0] to return the currently selected ListViewItem into an argument in a function that displays the text of the item into a textbox when selected. This method is set to the Listview_SelectedIndexChanged event. The problem is that when I selected a different item now after already previously selecting one, an error comes up that reads,I have a problem, I am using the method in list