如何测试fileStream？

Question

FileStream stream = new FileStream("test.xls", FileMode.OpenOrCreate)
ExcelWriter writer = new ExcelWriter(stream);
writer.BeginWrite();
writer.WriteCell (1, 0, "No");
    writer.WriteCell (1, 1, "Status");
    writer.WriteCell (1, 2, "Date");
    writer.WriteCell (1, 3, "Time");
    writer.WriteCell (1, 4, "Unit");
    writer.WriteCell (1, 5, "Total");
writer.EndWrite();
    stream.Close();

我在按钮中写了这个代码。当我第一次点击它工作时。但是当我再次点击它时出现错误：单声道system.io.ioexception共享违规路径....如何解决？请帮助。谢谢< / p>