WebRequest POST with both file and parameters

Question

I\'m trying to upload a file and a send along a few parameters to my site using .NET / C#. Having read a few tutorials that do either a few parameters or a file, I\'ve tried

Answer 1

The problem is that you're missing a '\n'. The following line:

string postData = "--" + boundary + "\nContent-Disposition: form-data\n";

should be:

string postData = "--" + boundary + "\nContent-Disposition: form-data\n\n";

And this line:

postData += "\n--" + boundary + "\nContent-Disposition: form-data; name=\"file\" filename=\"upload.pdf\" Content-Type: application/pdf\n\n"

is missing a '\n' before 'Content-Type'. It should be:

postData += "\n--" + boundary + "\nContent-Disposition: form-data; name=\"file\" filename=\"upload.pdf\"\nContent-Type: application/pdf\n\n"

Answer 2

I guess the immediate problem is a mismatch between the declared and the actual length.

Where did you miscalculated I am not sure but if I remember correctly the length should include every byte of the response (including headers) except for the first line.

To be sure I would build a simple html page to generate the post you want and examined the post with fiddler (or firebug)

Answer 3

Try to change

string postData = "--" + boundary + "\nContent-Disposition: form-data\n";

to

string postData = "\n\n--" + boundary + "\nContent-Disposition: form-data\n\n";

And better also replace all \n to \r\n. At least first two newlines worked for me solving "Header section has more than 10240 bytes (maybe it is not properly terminated)" problem.

And this code doesn't look correct:

postData += "myId=123&someFk=456";

My objective-C code for iPhone app which I am using and which works now looks like this:

NSMutableData *reqData = [NSMutableData data];
NSURL *encUrl;
encUrl = [NSURL URLWithString:[NSString url];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:encUrl];
request.HTTPMethod = @"POST";
request.timeoutInterval = kServerConnectionTimeout;
    NSString *stringBoundary = [NSString stringWithString:@"Multipart-Boundary"]; // TODO - randomize this
    NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=\"%@\"",stringBoundary];
    [request addValue:contentType forHTTPHeaderField: @"Content-Type"];

[reqData appendData:[[NSString stringWithFormat:@"\r\n\r\n--%@\r\n",stringBoundary] dataUsingEncoding:NSUTF8StringEncoding]];
for (id key in [self.parameters allKeys])
{
    if (![key isEqualToString:@"image"])
    {
        NSString *val = [self.parameters objectForKey:key];
        if (val != nil)
        {
            [reqData appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"\r\n",key] dataUsingEncoding:NSUTF8StringEncoding]];
            [reqData appendData:[[NSString stringWithFormat:@"Content-Type: text/plain\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
            [reqData appendData:[[NSString stringWithFormat:@"Content-Transfer-Encoding: 8bit\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
            [reqData appendData:[[NSString stringWithFormat:@"%@",val] dataUsingEncoding:NSUTF8StringEncoding]];
            [reqData appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",stringBoundary] dataUsingEncoding:NSUTF8StringEncoding]];
        }
    }
}

// send binary part last
if ([self.parameters objectForKey:@"image"])
{
    NSString *key  = @"image";
    NSData *imageData = [self.parameters objectForKey:key];
    if (imageData != nil)
    {
        [reqData appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"image\";filename=\"avatar.png\"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
        [reqData appendData:[[NSString stringWithFormat:@"Content-Type: image/png\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];

        [reqData appendData:[[NSString stringWithFormat:@"Content-Transfer-Encoding: binary\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
        [reqData appendData:imageData];
        [reqData appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",stringBoundary] dataUsingEncoding:NSUTF8StringEncoding]];
    }
}
NSString * dataLength = [NSString stringWithFormat:@"%d", [reqData length]];
[request addValue:dataLength forHTTPHeaderField:@"Content-Length"];

request.HTTPBody = reqData;
NSLog(@"postBody=%@", [[NSString alloc] initWithData:reqData encoding:NSASCIIStringEncoding]);

Hope this helps somebody.