C# 文件异常 : cannot access the file because it is being used by another process

Question

我正在尝试从网络上下载文件并将其保存在本地，但出现异常:

C# The process cannot access the file 'blah' because it is being used by another process.

这是我的代码:

File.Create("data.csv");  // create the file
request = (HttpWebRequest)WebRequest.CreateDefault(new Uri(url));
request.Timeout = 30000;
response = (HttpWebResponse)request.GetResponse();

using (Stream file = File.OpenWrite("data.csv"), // <-- Exception here
    input = response.GetResponseStream())
{
    // Save the file using Jon Skeet's CopyStream method
    CopyStream(input, file);
}

我已经看到许多其他问题都有相同的异常(exception)，但似乎没有一个适用于此。有帮助吗？

更新:
感谢您的回答!删除 File.Create(...) 修复它!

关于OpenWrite 文档的评论:有点误导，简要说明说:

Opens an existing file for writing.

详细描述说:

If the file exists, it is opened for writing at the beginning. The existing file is not truncated.

2.0 更新:
看起来 IntelliSense/F1 和联机文档之间存在差异。我认为它应该是一样的，因为我允许 F1 在显示文档时连接到网络。

Answer 1

File.Create 返回一个 FileStream - 您没有关闭它。这意味着在终结器关闭现有流之前，您将无法打开写入同一文件的另一个流。

只是摆脱对 File.Create 的调用 - File.OpenWrite 无论如何都会创建它。或者，保持 FileStream 写入:

using (Stream file = File.Create("data.csv"))
{
    request = (HttpWebRequest)WebRequest.CreateDefault(new Uri(url));
    request.Timeout = 30000;
    using (var response = (HttpWebResponse)request.GetResponse())
    using (Stream input = response.GetResponseStream())
    {
        // Save the file using Jon Skeet's CopyStream method
        CopyStream(input, file);
    }
}

请注意，我还在这里处理了 WebResponse，您应该这样做以确保连接已释放到连接池。