The ListView.SelectedIndices property will not contain any indexes if the property is accessed before the System.Windows.Forms.ListView handle is created, which typically occurs when the System.Windows.Forms.ListView is initially loaded for display in the form. You can check to see if the handle is created with the Control.IsHandleCreated property. When the ListView.MultiSelect property is set to true, this property returns a collection containing the indexes of all items that are selected in the System.Windows.Forms.ListView. For a single-selection System.Windows.Forms.ListView, this property returns a collection containing a single element containing the index of the only selected item in the System.Windows.Forms.ListView. For more information on the tasks that can be performed with the items in the collection, see System.Windows.Forms.ListView.SelectedIndexCollection.

If you want to obtain a collection of the items that are selected in the System.Windows.Forms.ListView control, instead of the index positions of the items that are selected, use the ListView.SelectedItems property.