File Transfer with WCF

I’m very much impressed with your presentation and technical abilities. I request you to share the File Upload service code in detail so that I can implement in one of my services. Thanks in advance.

Can you share the implementation based on a class implementing IXmlSerializable? I am new to .net and came recently from java world

Hi George, thank you for stepping by. Any particular reason why you need to go through the XMLSerializable route?

Hi Stefano,

I would really like to batch the transfer at times so as far as I understand XMLSerializable gives better control during streaming.
So I thought of trying that way out.

George,

there’s nothing that prevents using something along the lines of the solution outlined in this post from being invoked from a batch file. As a matter of fact, the proxy that I created from this service is invoked from legacy C++ code through COM.

As far as I know, implementing IXMLSerializable can give you more control on the way the objects are serialized. But unless you need to transfer complex metadata describing the files being moved back and forth, default WCF serialization should do quite fine.

Hi, Stefano:

I’ve been looking into a WCF implementation to transfer large binary files (images) around the 250-300 MB range. Much like you, I need the filename. However, my concern is that using the message contract will cause the binary file to be serialized into xml. Is this true or am I way off base here?

Am I going to trade efficiency of a straight stream sans the filename for a complex and large overhead using the message contract just to have the luxury (ahem – necessity) of including a filename?

Any insights you can provide from your experiences?

Eric,

be sure to set the binding message encoding to MTOM (see my config above). MTOM is especially suited to exchange large binary data without using base64 conversion (which increases the size by 1/3).

Read more about MTOM here

Hello Stefano,

Thank you for sharing this helpful information. Is it possible if you share the source code or at least the implemention of UploadFile and DownloadFile.

Thank you,

Hi Anita,

unfortunately I cannot share the whole source code without violating the intellectual property of my company. I’ll try to post a scheleton implementation of the UploadFile and Download file as soon as possible.

Anita,
see my latest post for a rough implementation.

Vinay,
see my latest post for a rough implementation.

Excellent! Thank you

Hello Stefano,

Could you please provide me the code file for File Upload Service. I would like to test it out and see..

Thanks.

Pathmini

Pathmini,

have you looked at http://stefanoricciardi.com/2009/10/02/file-transfer-with-wcf-part-ii/ ? There you can find a scheleton of the server implementation.

Hello, Stefano!

Thank you for your articale!

Why I can’t just simply use the following construction to transfer files:

[DataContract]
public class UserDataFile
{

private FileStream _toStore;
private int _groupId;

public UserDataFile(FileStream stream, int groupId)
{
ToStore = stream;
GroupId = groupId;

}

[DataMember]
public FileStream ToStore
{
get { return _toStore; }
set { _toStore = value; }
}

[DataMember]
public int GroupId
{
get { return _groupId; }
set { _groupId = value; }
}

Anton,

have you tried the approach you outlined? What errors did you get?

I guess you are not interested in trying streaming since there are limitations on what the DataContract can be in this case, as highlighted at the top of my post.

Hello Stefano!
Thank you for your reply.

I need to transfer big files from client to service and back. On the service side I need to store it in DB. For this purposes I use ORM that maps varbinary(MAX) to byte[]. So it seems good to transfer files like byte[], but AFAIK, the best way for sending big files is streaming. But when I use stream I can’t get it’s length (throws exception) and as result I can’t convert it to byte[]. Maybe you can suggest something.

Thanks in advance.

Anton,
the scenario you are describing is similar to mine. I suggest you try the approach I suggested above and see whether it can help you.

I have been able to use streaming and to pass the parameters I needed once I switched to using Message Contracts. It’s not that much more work to do than plain DataContracts.

how can i implement pause/resume in upload or download?

In my scenario if connection is dropped, i want to keep the uploaded / downloaded file and resume from there.

any pointers will be helpful.

Thanks

Prashant,

I don’t have a first-hand experience on this topic. You might want to have a look at the following question on Stack-Overflow for some pointers: http://stackoverflow.com/questions/1048330/pause-resume-upload-in-c

Hi Stefano,

Please, can you tell me how to consume this service. I have already created the service but on the client side when i create the object of the service and through the object when i call the DowloadFile method then it does not allow me to specify parameter for it. So basically below is what its allowing me to do
Service1 obj = new Service1();
obj.DownloadFile();

But my download file method looks like below

public FileDownloadReturnMessage DownloadFile(FileDownloadMessage request)
{
}

Please advise

Amit,

I am not sure I understood your problem. Anyway, my client looks something like the (sorry about the poor formatting):


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

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);
}
}


Stefano,

Thanks for the reply.

My apologies if i didn’t make myself clear. My problem is below

I am using VS.NET 2008

Step 1: I add a web reference on the web service i have hosted on IIS into my web project.

Step 2: I create an object of my .svc file in my web project like:
Service1 objService = new Service1();

this Service1 class has the below code. I have modified your original code little but

public FileDownloadReturnMessage DownloadFile(FileDownloadMessage request)
{
try
{
string serverFileName = request.FileMetaData.LocalFileName;
Stream fs = new FileStream(serverFileName, FileMode.Open);
return new FileDownloadReturnMessage(“abc.pdf”, fs);
}
catch (IOException e)
{
throw new FaultException(e);
}
}

Now when try to access DownloadFile method using this objService object then it does not allow me to specify a parameter to this method. All it gives me is an option to select a parameterless “DownloadFile” method.

So for ex: if i do below it gives a compile time error

objService.DownloadFile(request)

but it allows me to do :
objService.DownloadFile()

Please advise.

Appreciate your help

Amit,

looks like the client you are using is not proper, probably something went wrong in the creation of the proxy

There are hundreds of resources online explaining how to create a proxy for a WCF service that surely can do a better job than I would do. I suggest to check those out.

thanks for the reply,

yeah i thought it might be the proxy but then i added another method in the web service below:

[OperationContract(IsOneWay = false)]
FileDownloadReturnMessage DownloadFile(FileDownloadMessage request);

[OperationContract()]
string TestMethod(string name);

I can see TestMthod is running fine at my client but the DownloadFile method does not accept any parameters where it should be accepting a parameter of type FileDownloadMessage.

So i believe there is no issues with my proxy. I must have done some mistake in my web service itself