问题描述
我想从客户端计算机上将大量数据上传到Web服务器 .我跳到了PushStreamContent，所以我可以直接写到流中，因为结果的大小各不相同，而且可能很大.
I would like to upload a large amount of data to a web server from a client machine. I jumped right to PushStreamContent so I could write directly to the stream, as the results vary in size and can be rather large.
流程如下:
User runs query > Reader Ready Event Fires > Begin Upload
一旦触发ready事件，侦听器将拾取它并遍历结果集，并以多部分形式上载数据:
Once the ready event is fired, the listener picks it up and iterates over the result set, uploading the data as a multipart form:
Console.WriteLine("Query ready, uploading");
byte[] buffer = new byte[1024], form = new byte[200];
int offset = 0, byteCount = 0;
StringBuilder rowBuilder = new StringBuilder();
string builderS;
var content = new PushStreamContent(async (stream, httpContent, transportContext) =>
//using (System.IO.Stream stream = new System.IO.FileStream("test.txt", System.IO.FileMode.OpenOrCreate))
{
int bytes = 0;
string boundary = createFormBoundary();
httpContent.Headers.Remove("Content-Type");
httpContent.Headers.TryAddWithoutValidation("Content-Type", "multipart/form-data; boundary=" + boundary);
await stream.WriteAsync(form, 0, form.Length);
form = System.Text.Encoding.UTF8.GetBytes(createFormElement(boundary, "file"));
await stream.WriteAsync(form, 0, form.Length);
await Task.Run(async () =>
{
foreach (var row in rows)
{
for (int i = 0; i < row.Length; i++)
{
rowBuilder.Append(row[i].Value);
if (i + 1 < row.Length)
rowBuilder.Append(',');
else
{
rowBuilder.Append("\r\n");
}
}
builderS = rowBuilder.ToString();
rowBuilder.Clear();
byteCount = System.Text.Encoding.UTF8.GetByteCount(builderS);
bytes += byteCount;
if (offset + byteCount > buffer.Length)
{
await stream.WriteAsync(buffer, 0, offset);
offset = 0;
if (byteCount > buffer.Length)
{
System.Diagnostics.Debug.WriteLine("Expanding buffer to {0} bytes", byteCount);
buffer = new byte[byteCount];
}
}
offset += System.Text.Encoding.UTF8.GetBytes(builderS, 0, builderS.Length, buffer, offset);
}
});
await stream.WriteAsync(buffer, 0, offset);
form = System.Text.Encoding.UTF8.GetBytes(boundary);
await stream.WriteAsync(form, 0, form.Length);
await stream.FlushAsync(); //pretty sure this does nothing
System.Diagnostics.Debug.WriteLine("Wrote {0}.{1} megabytes of data", bytes / 1000000, bytes % 1000000);
我认为如果我是服务器，上面的代码会很好用，只需添加stream.Close();就可以完成它，但是由于我是这里的客户端，关闭它会导致错误(TaskCancelled).我想等待读取也无济于事，因为除非我明确关闭流，否则PushStreamContent不会结束请求.话虽如此，写入文件将产生我希望上传的文件，因此一切都写得很好.
I think the code above would work great if I were the server, just adding stream.Close(); would finish it, however since I am the client here closing it causes an error (TaskCancelled). Waiting to read doesn't do anything either, I presume because the PushStreamContent doesn't end the request unless I explicitly close the stream. That being said, writing to a file produces exactly what I expect to be uploaded so everything writes perfectly.
关于我在这里可以做什么的任何想法?我可能完全滥用了PushStreamContent，但似乎应该是一个合适的用例.
Any ideas on what I can do here? I might be totally misusing PushStreamContent but it seems like this should be an appropriate use case.
推荐答案
因此，该解决方案起初有点令人困惑，但似乎很有意义，而且也许更重要的是，它可行:
So the solution is a little confusing at first but it seems to make sense and perhaps more importantly, it works:
using(var content = new MultipartFormDataContent())
{
var pushContent = new PushStreamContent(async (stream, httpContent, transportContext) =>
{
//do the stream writing stuff
stream.Close();
});
content.add(pushContent);
//post, put, etc. content here
}
之所以可行，是因为传递给PushStreamContent方法的流不是实际的请求流，而是由HttpClient处理的流，就像将文件添加到请求流中一样.结果，将其关闭表示HttpContent此部分的输入结束，并允许完成请求.
This works because the stream passed to the PushStreamContent method is not the actual request stream, it's a stream handled by the HttpClient, just like adding a file to a request stream. As a result, closing it signals the end of input for this part of the HttpContent and allows the request to be finalized.
这篇关于使用PushStreamContent从HTTPClient上传的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！