Uploading Large Files Through Web Service

Introduction

In this article, I am going to explain how to upload large files using web service method. We will not need to change anything in IIS or web.config (maximum request size) developed in Visual Studio 2008.

Using the Code

I have created a web method to accept file name, bytes (array) and offset. Here is the function.

/// <summary>
/// This function is used to append chunk of bytes to a file name. 
/// If the offset starts from 0 means file name should be created.
/// </summary>
/// <param name="FileName">File Name</param>
/// <param name="buffer">Buffer array</param>
/// <param name="Offset">Offset</param>
/// <returns>boolean: true means append is successfully</returns>
[WebMethod]
public bool UploadFile(string FileName, byte[] buffer, long Offset)
{
bool retVal = false;
try
{
// setting the file location to be saved in the server. 
// reading from the web.config file 
string FilePath = 
	Path.Combine(ConfigurationManager.AppSettings["upload_path"], FileName);

if (Offset == 0) // new file, create an empty file
File.Create(FilePath).Close();
// open a file stream and write the buffer. 
// Don't open with FileMode.Append because the transfer may wish to 
// start a different point
using (FileStream fs = new FileStream(FilePath, FileMode.Open, 
	FileAccess.ReadWrite, FileShare.Read))
{
fs.Seek(Offset, SeekOrigin.Begin);
fs.Write(buffer, 0, buffer.Length);
}
retVal = true;
}
catch (Exception ex)
{
//sending error to an email id
common.SendError(ex);
}
return retVal;
}

In the function, I am setting the file location to be saved in the server. I have put it in a appSetting section in the web.config file.

<add key="upload_path" value="d:\files\"></add>

How to Consume the Web Method

I have created a Windows application (C#). I have put a button. On the button click, I have put the following code:

//the file that we want to upload
string FilePath="d:\somefile.pdf";
int Offset = 0; // starting offset.

//define the chunk size
int ChunkSize = 65536; // 64 * 1024 kb

//define the buffer array according to the chunksize.
byte[] Buffer = new byte[ChunkSize];
//opening the file for read.
FileStream fs = new FileStream(FilePath, FileMode.Open, FileAccess.Read);
//creating the ServiceSoapClient which will allow to connect to the service.
WSservice.ServiceSoapClient soap_client = new WSservice.ServiceSoapClient();
try
{
long FileSize = new FileInfo(FilePath).Length; // File size of file being uploaded.
// reading the file.
fs.Position = Offset;
int BytesRead = 0;
while (Offset != FileSize) // continue uploading the file chunks until offset = file size.
{
BytesRead = fs.Read(Buffer, 0, ChunkSize); // read the next chunk 
	// (if it exists) into the buffer. 
	// the while loop will terminate if there is nothing left to read
// check if this is the last chunk and resize the buffer as needed 
// to avoid sending a mostly empty buffer 
// (could be 10Mb of 000000000000s in a large chunk)
if (BytesRead != Buffer.Length)
{
ChunkSize = BytesRead;
byte[] TrimmedBuffer = new byte[BytesRead];
Array.Copy(Buffer, TrimmedBuffer, BytesRead);
Buffer = TrimmedBuffer; // the trimmed buffer should become the new 'buffer'
}
// send this chunk to the server. it is sent as a byte[] parameter, 
// but the client and server have been configured to encode byte[] using MTOM. 
bool ChunkAppened = soap_client.UploadFile(Path.GetFileName(FilePath), Buffer, Offset);
if (!ChunkAppened)
{
break;
}

// Offset is only updated AFTER a successful send of the bytes. 
Offset += BytesRead; // save the offset position for resume
}
}
catch (Exception ex)
{
}
finally
{
fs.Close();
}

History

• 25^th October, 2009: Initial post