How do I resolve the “maximum request length exceeded” exception?

Question

When I upload an image I had this error:

maximum request length exceeded

How can I fix this problem?

Answer 1

That's not a terrific way to do it as you're basically opening up your server to DoS attacks allowing users to submit immense files. If you know that the user should only be uploading images of a certain size, you should be enforcing that rather than opening up the server to even larger submissions.

To do that you can use the example below.

As I was been moaned at for posting a link, I've added what I ultimately implemented using what I learned from the link I previously posted - and this has been tested and works on my own site...it assumes a default limit of 4 MB. You can either implement something like this, or alternatively employ some sort of third-party ActiveX control.

Note that in this case I redirect the user to the error page if their submission is too large, but there's nothing stopping you from customising this logic further if you so desired.

I hope it's useful.

public class Global : System.Web.HttpApplication {
    private static long maxRequestLength = 0;

    /// 

    /// Returns the max size of a request, in kB
    /// 
    /// 
    private long getMaxRequestLength() {

        long requestLength = 4096; // Assume default value
        HttpRuntimeSection runTime = ConfigurationManager.GetSection("system.web/httpRuntime") as HttpRuntimeSection; // check web.config
        if(runTime != null) {
            requestLength = runTime.MaxRequestLength;
        }
        else {
            // Not found...check machine.config
            Configuration cfg = ConfigurationManager.OpenMachineConfiguration();
            ConfigurationSection cs = cfg.SectionGroups["system.web"].Sections["httpRuntime"];
            if(cs != null) {
                requestLength = Convert.ToInt64(cs.ElementInformation.Properties["maxRequestLength"].Value);
            }
        }
        return requestLength;
    }

    protected void Application_Start(object sender, EventArgs e) {
        maxRequestLength = getMaxRequestLength();
    }

    protected void Application_End(object sender, EventArgs e) {

    }

    protected void Application_Error(object sender, EventArgs e) {
        Server.Transfer("~/ApplicationError.aspx");
    }

    public override void Init() {
        this.BeginRequest += new EventHandler(Global_BeginRequest);
        base.Init();
    }

    protected void Global_BeginRequest(object sender, EventArgs e) {

        long requestLength = HttpContext.Current.Request.ContentLength / 1024; // Returns the request length in bytes, then converted to kB

        if(requestLength > maxRequestLength) {
            IServiceProvider provider = (IServiceProvider)HttpContext.Current;
            HttpWorkerRequest workerRequest = (HttpWorkerRequest)provider.GetService(typeof(HttpWorkerRequest));

            // Check if body contains data
            if(workerRequest.HasEntityBody()) {

                // Get the total body length
                int bodyLength = workerRequest.GetTotalEntityBodyLength();

                // Get the initial bytes loaded
                int initialBytes = 0;
                if(workerRequest.GetPreloadedEntityBody() != null) {
                    initialBytes = workerRequest.GetPreloadedEntityBody().Length;
                }
                if(!workerRequest.IsEntireEntityBodyIsPreloaded()) {
                    byte[] buffer = new byte[512000];

                    // Set the received bytes to initial bytes before start reading
                    int receivedBytes = initialBytes;
                    while(bodyLength - receivedBytes >= initialBytes) {

                        // Read another set of bytes
                        initialBytes = workerRequest.ReadEntityBody(buffer, buffer.Length);

                        // Update the received bytes
                        receivedBytes += initialBytes;
                    }
                    initialBytes = workerRequest.ReadEntityBody(buffer, bodyLength - receivedBytes);
                }
            }

            try {
                throw new HttpException("Request too large");
            }
            catch {
            }

            // Redirect the user
            Server.Transfer("~/ApplicationError.aspx", false);
        }
    }