C＃文件例外：因为它正在被其他进程无法访问该文件 [英] C# File Exception: cannot access the file because it is being used by another process

问题描述

我试图从网上下载一个文件并将其保存在本地，但我得到一个异常：

I'm trying to download a file from the web and save it locally, but I get an exception:

C＃过程因为它正由
其他进程无法访问文件
'胡说'。

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);
}

我已经看到了同样的异常其他许多问题，但他们没有似乎在此适用。任何帮助

I've seen numerous other questions with the same exception, but none of them seem to apply here. Any help?

更新：结果
感谢您的答案！删除 File.Create（...）定了！

的文档上的一个评论 OpenWrite ：这是一个有点误导，简要描述说：

One comment on the documentation of OpenWrite: it is a little misleading, the brief description says:

打开一个的 。现有的的文件进行写入

Opens an existing file for writing.

详细描述说：

的如果该文件存在，它被打开的为开头
写作。现有的
文件不被截断。

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

更新2.0：结果
检查看起来差异是智能感知/ F1和在线文档之间。我认为这应该是一样的，因为我让F1连接时，它显示文档的网页。

Update 2.0:
It looks like the discrepancy is between IntelliSense/F1 and the online documentation. I thought it should be the same since I allow F1 to connect to the web when it's displaying documentation.

推荐答案

File.Create 返回的FileStream - 这你不关闭。这意味着你将无法打开的其他的流写入到同一个文件，直到终结已关闭现有流。

File.Create returns a FileStream - which you're not closing. That means you won't be able to open another stream writing to the same file until the finalizer has closed the existing stream.

刚刚得到摆脱呼叫到 File.Create - File.OpenWrite 无论如何都会创建它。另外，保持的FileStream 周围写：

Just get rid of the call to File.Create - File.OpenWrite will create it anyway. Alternatively, keep the FileStream around to write to:

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，我还配置了<$的C $ C> WebResponse类在这里，你应该做的，以确保连接被释放到连接池。

Note that I'm also disposing of the WebResponse here, which you should do to make sure the connection is freed to the connection pool.

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