// Prim's Algorithm. private void toolStripRightSaveMinimumSpanTree_Click(object sender, EventArgs e) { if (ListBoxImport.SelectedIndex != -1) { graphAlObj.GetMST(ListBoxImport.SelectedItem.ToString()); ListBoxResults.Items.Add("MST: " + ListBoxImport.SelectedItem); } else { MessageBox.Show("You have not selected a value from the list.", "Caution", MessageBoxButtons.OK, MessageBoxIcon.Error); } }