File Transfer with WCF

Stefano,

I have a question.

Can i use datacontracts/datamembers for streaming (download) instead of message contract.

If yes then will it improve performance?

Please advise

thanks
Amit

Stefano,

Please, Can you share the code of SaveFile(response.FileByteStream, localFile); methos as well. I want to see how the stream is converted to file back again. Also can i use the your technique of WCF service for downloading zip files

Thanks
James

Stephano, I implemented an MTOM webservice that transfers files using webservices.
I used Axis2 and Java. I’m trying to make a decision if this could be an architecture for a large project where clients will be sending files using web services. I’d like your opinion about the feasability of MTOM and possible problems. Is there a size limitation? How do I make sure the file transferred completely to the client/server? Is there a way to send it with chunks.. Any help will be appreciated.
Thanks
Nadia

Dear Stefano,
Thank you verymuch for sharing your knowledge on WCF file transfer. Three months I googled a lot on the topic. I couldnot relevant information except in WCF samples by MSDN. Can you please provide the code in VB as well. I tried to convert the code ,but it is showing errors.

Dear Stefano,
Thank for your reply. I tried in C# itself. Same error both in C# and VB.
Error:
“The type or namespace ‘FileTypeEnum’ could not be found(are you missing a using directive or an assembly reference)”

Raghu,

unfortunately these are not “copy and paste into your app” snippets. They
are somehow extracted from the larger context of our line-of-business
application.

The compiler is complaining because you have not defined the FileTypeEnum.
That enumeration is only meaningful within our own application (it describes
which kind of file is being transferred; according to the file type a
specific post-upload operation may be performed).

My suggestion is to remove it wherever it is referenced if that is not
something you need, or create your own enumeration.

Stefano

Davide,

this looks like a server issue.
Davide,

this looks like a server configuration issue. Try increasing the maxRequestLegth of the httpRuntime.

Mine is set as follows:

Reference: http://msdn.microsoft.com/en-us/library/e1f13641(v=VS.90).aspx

I am from islamababd, great article! I am impressed by your active support in multiple issues addressed here. I implemented service and it is now working fine with upload and download. Upload is working fine even with same file mutiple times.
Download first time is OK. If I download same file second time, it fails on client side. I debuged service download method, at the time of opening file stream exception is: The process cannot access the file ‘C:workTest.txt’ because it is being used by another process.
Any clue?
I am closing FileByteStream on client side. closing IClientChannel proxy too.
Basharat Hussain

Hi Stefano,

Great article – I am also experiencing the same issues as Basharat .. The first time I access a file using the service it is fine, but the file is then locked by the process and cannot be written to subsequently.

Do you know of a way to close the stream on the download method (as it gets returned in the method it cannot be closed).

Many thanks in advance,

Adam

And for me it works also if I try to write to the file just downloaded:

[Test()]
public void it_should_be_possible_to_download_a_generic_file_twice_can_be_written()
{
IFileTransferProxy proxy = new FileTransferProxy();
string localFile = Path.Combine(basePath, “localFoo.txt”);

proxy.DownloadFileWithName(localFile, “foo.txt”, serviceUrl);

using (FileStream s = new FileStream(localFile, FileMode.Open, FileAccess.Write))
{
Assert.IsTrue(s.CanWrite, “cannot write the first time”);
}

// try it again
proxy.DownloadFileWithName(localFile, “foo.txt”, serviceUrl);
using (FileStream s = new FileStream(localFile, FileMode.Open, FileAccess.Write))
{
Assert.IsTrue(s.CanWrite, “cannot write the second time”);
}

// cleanup
File.Delete(localFile);
}

Your server side code looks very similar to my own.

On the client side, I have something like the following:

private void IssueDownloadRequest(string localFile, string serviceUrl, FileDownloadMessage request)
{
this.service = this.proxy.OpenProxy(serviceUrl);

try
{
using (FileDownloadReturnMessage response = this.service.DownloadFile(request))
{
if (response != null && response.FileByteStream != null)
{
SaveFile(response.FileByteStream, localFile);
}
}

this.proxy.CloseProxy(this.service);
}
catch (Exception e)
{
throw new FileTransferProxyException(“Error while downloading the file”, e);
}
finally
{
// we expect the stream returned from the server to be closed by the
// server itself so nothing to be done with it here. Just abort
// the proxy if needed.
this.proxy.AbortProxyIfNeeded(this.service);
}
}

// this will throw if something is wrong
private static void SaveFile(Stream saveFile, string localFilePath)
{
const int bufferSize = 65536; // 64K

using (FileStream outfile = new FileStream(localFilePath, FileMode.Create))
{
byte[] buffer = new byte[bufferSize];
int bytesRead = saveFile.Read(buffer, 0, bufferSize);

while (bytesRead > 0)
{
outfile.Write(buffer, 0, bytesRead);
bytesRead = saveFile.Read(buffer, 0, bufferSize);
}
}
}

The proxy you see in the integration tests is just a COM-visible wrapper around these features, it adds no special handling to the request.

Basharat: I could not fix the problem either way. by calling IssueDownloadRequest() twice or Adam’s trick.
First way same behavior, stream is not closed on second time and raise exception. Server code is similar in WCF. Client code is bit different like “FileDownloadReturnMessage response” is not disposable in my case so not have “using” block. Here is mine code:

In Adam’s method, When I call stream.Flush it creashes with “Specified method is not supported” exception.

Here is my code:

private void IssueDownloadRequest(string baseFolder, FileDownloadMessage request)
{
var proxy = OpenProxy(“http://localhost/LargeDataService/FileTransferService.svc”);
FileDownloadReturnMessage response = null;
try
{
//AttemptToCloseStream(request.FileMetaData.RemoteFilename);
response = proxy.DownloadFile(request);
if (response != null && response.FileByteStream != null)
{
string localFilePath = Path.Combine(baseFolder, request.FileMetaData.RemoteFilename);
SaveFile(response.FileByteStream, localFilePath);
response.FileByteStream.Close();
//OpenStreams.Add(request.FileMetaData.RemoteFilename, response.FileByteStream);
MessageBox.Show(string.Format(“File downloaded successfully to path : {0}”, localFilePath));
}

}
catch (Exception e)
{
throw e;// new FileTransferProxyException(e);// { InnerException = e, Source = “Download File Exception”};
}
finally
{
// we expect the stream returned from the server to be closed by the
// server itself so nothing to be done with it here. Just abort
// the proxy if needed.
//this.proxy.AbortProxyIfNeeded(this.service);
CloseProxy(proxy);
}
}

and here is proxy
public IFileTransferService OpenProxy(string serviceUrl)
{
Debug.Assert(!string.IsNullOrEmpty(serviceUrl));

var binding = new BasicHttpBinding();
binding.Name = “basicHttpStream”;
binding.MaxReceivedMessageSize = 2147483647;
binding.TransferMode = TransferMode.Streamed;
binding.MessageEncoding = WSMessageEncoding.Mtom;

var channelFactory = new ChannelFactory(
binding,
new EndpointAddress(serviceUrl));

return channelFactory.CreateChannel();
}

public void CloseProxy(object sender)
{
IClientChannel channel = (IClientChannel)sender;
try
{
channel.Close();
}
catch
{
channel.Abort();
}
}
Any suggestion will be greatly appriciated

Basharat,

as I mentioned earlier I am not facing the same issues you are experiencing with the following sequence:
1) download file x
2) open file x for write
3) close x
4) goto 1

There must be something different in your scenario that causes the stream not to be closed properly. Unfortunately, it’s quite difficult to understand the behavior without stepping into the code with a debugger.

@razzi
Thanks a lot, yes it worked:)
Basharat

I would like to implement multiple downloads for single client. For example there are certain files intended for download to particular client every day. These files are uploaded by subordinate offices.
For the present I am sending a query to the webserver to find if there are any files. If there are files, array of file names will be returned to client.
Each file name in the array will be passed to download file contract till all the filenames in the array are downloaded.

Can I pass array of file names at server side itself. Please help…..

I am new in this technology could you please provide small hint how to achieve this.

Raghu,

as you can see from the number of replies I have made in this post, I *am* trying to help. However this is just a personal blog and not a question & answer site (like, say, StackOverflow).

I have presented here a possible solution to a problem (sending files via WCF), hoping that this would inspire other people with similar problems. I am not a Microsoft MVP.

It seems, though, that you need something more and you expect me to provide the solution to your specific problem. I don’t have code ready to solve it and it would take me hours just to understand your scenario, put the code together and test it until it works correctly.

can you provide ‘FileTypeEnum’ Enum code?

Hi, I am interested to know if you can pass the stream across multiple WCF services i.e., read the file and create stream in asp.net – pass it to wcf service – this wcf service in turn passes it to another wcf service which saves it to file system. I have a similar type of requirement but I want to know if it is possible to stream across multiple wcf services without storing it in memory in every level.

This has been asked and replied above.
Cheers,
 Stefano