对话框类层次 CommonDialog FileDialog ColorDialog FontDialog FolderBrowseDialog PrintDialog Form OpenFileDialog SaveFileDialog PrintPreViewDialog ShowDialog():显示一个通用对话框 该方法返回一个DialogResulta枚举4 对话框类层次 FileDialog PrintDialog CommonDialog ColorDialog FontDialog FolderBrowseDialog OpenFileDialog SaveFileDialog Form PrintPreViewDialog ShowDialog():显示一个通用对话框 该方法返回一个DialogResult枚举