How to upload large files using MVC 4?

Current Version

According to the detailed error description of IIS 8.0, which is the version I used at the time I wrote this answer, you need to verify the configuration/system.webServer/security/requestFiltering/requestLimits@maxAllowedContentLength setting in the ApplicationHost.config or Web.config file. That means you need to include:

<requestLimits maxAllowedContentLength="20971520000"></requestLimits>

inside configuration/system.webServer/security/requestFiltering tag tree. Just in case you lack the imagination to visualize where it goes, the full code block goes like the following:

<configuration>
    <system.webServer>
        <security>
            <requestFiltering>
                <requestLimits maxAllowedContentLength="20971520000"></requestLimits>
            </requestFiltering>
        </security>
    </system.webServer>
</configuration>

Visual Studio 2010/.Net Framework 4 and Before

It is also possible that legacy web applications created with VS2008/10 and/or .Net Framework 3.5/4 may still be looking for this configuration via configuration/system.web/httpRuntime@maxRequestLength, but as evidenced by the linked page, it is no longer available, although HttpRuntime Class, which doesn't apply to this scenario, still exists since .Net Framework 1.1. If this is the case, you need to include:

<httpRuntime maxRequestLength="20971520000" />

inside configuration/system.web/httpRuntime tag tree. Once again, just in case you lack the comprehensibility to figure out where it gets inserted, the full code block looks something like the following:

<configuration>
    <system.web>
        <httpRuntime maxRequestLength="20971520000" />
    </system.web>
</configuration>

The file size number is just an arbitrary number (20,000 MB – not 20 GB, which would rather be 21,474,836,480) to show as a demo. Unless you're coding the website for a tight security group who has a need to upload large files, you shouldn't allow this big of a file size being uploaded to your web server.

The solution is based on Jonathan's code here. If you want to upload a large file, something like 1Gbyte video file, you have to chuck the file and send it through several request (one request gives time out). first you set the max limit for client and server side in Web.config as discussed in other answers.

<system.webServer>
 <security>
  <requestFiltering>
    <requestLimits maxAllowedContentLength="2147483647" />
  </requestFiltering>
 </security>
<system.webServer>

and

<system.web>
  <httpRuntime targetFramework="4.5" maxRequestLength="2147483647" />
</system.web>

then chunk the file, and send each chuck, wait for response and send the next chunk. here is the html (VideoDiv work as upload panel), javascript (jQuery) and controller code.

    <div id="VideoDiv">
        <label>Filename:</label>
        <input type="file" id="fileInput" /><br/><br/>
        <input type="button" id="btnUpload" value="Upload a presentation"/><br/><br/>
        <div id="progressbar_container" style="width: 100%; height: 30px; position: relative; background-color: grey; display: none">
            <div id="progressbar" style="width: 0%; height: 100%; position: absolute; background-color: green"></div>
            <span id="progressbar_label" style="position: absolute; left: 35%; top: 20%">Uploading...</span>
        </div>
    </div>

Javascript code to chuck, call controller and update progressbar:

        var progressBarStart = function() {
            $("#progressbar_container").show();
        }

        var progressBarUpdate = function (percentage) {
            $('#progressbar_label').html(percentage + "%");
            $("#progressbar").width(percentage + "%");
        }

        var progressBarComplete = function() {
            $("#progressbar_container").fadeOut(500);
        }

        var file;

        $('#fileInput').change(function(e) {
            file = e.target.files[0];
        });

        var uploadCompleted = function() {
            var formData = new FormData();
            formData.append('fileName', file.name);
            formData.append('completed', true);

            var xhr2 = new XMLHttpRequest();
            xhr2.onload = function() {
                progressBarUpdate(100);
                progressBarComplete();
            }
            xhr2.open("POST", "/Upload/UploadComplete?fileName=" + file.name + "&complete=" + 1, true);
            xhr2.send(formData);
        }

        var multiUpload = function(count, counter, blob, completed, start, end, bytesPerChunk) {
            counter = counter + 1;
            if (counter <= count) {
                var chunk = blob.slice(start, end);
                var xhr = new XMLHttpRequest();
                xhr.onload = function() {
                    start = end;
                    end = start + bytesPerChunk;
                    if (count == counter) {
                        uploadCompleted();
                    } else {
                        var percentage = (counter / count) * 100;
                        progressBarUpdate(percentage);
                        multiUpload(count, counter, blob, completed, start, end, bytesPerChunk);
                    }
                }
                xhr.open("POST", "/Upload/MultiUpload?id=" + counter.toString() + "&fileName=" + file.name, true);
                xhr.send(chunk);
            }
        }

        $("#VideoDiv").on("click", "#btnUpload", function() {
            var blob = file;
            var bytesPerChunk = 3757000;
            var size = blob.size;

            var start = 0;
            var end = bytesPerChunk;
            var completed = 0;
            var count = size % bytesPerChunk == 0 ? size / bytesPerChunk : Math.floor(size / bytesPerChunk) + 1;
            var counter = 0;
            progressBarStart();
            multiUpload(count, counter, blob, completed, start, end, bytesPerChunk);
        });

and here is the upload controller to store the chucnk in ("App_Data/Videos/Temp") and later merge them and store in ("App_Data/Videos"):

public class UploadController : Controller
{
    private string videoAddress = "~/App_Data/Videos";

    [HttpPost]
    public string MultiUpload(string id, string fileName)
    {
        var chunkNumber = id;
        var chunks = Request.InputStream;
        string path = Server.MapPath(videoAddress+"/Temp");
        string newpath = Path.Combine(path, fileName+chunkNumber);
        using (FileStream fs = System.IO.File.Create(newpath))
        {
            byte[] bytes = new byte[3757000];
            int bytesRead;
            while ((bytesRead=Request.InputStream.Read(bytes,0,bytes.Length))>0)
            {
                fs.Write(bytes,0,bytesRead);
            }
        }
        return "done";
    }

    [HttpPost]
    public string UploadComplete(string fileName, string complete)
    {
        string tempPath = Server.MapPath(videoAddress + "/Temp");
        string videoPath = Server.MapPath(videoAddress);
        string newPath = Path.Combine(tempPath, fileName);
        if (complete=="1")
        {
            string[] filePaths = Directory.GetFiles(tempPath).Where(p=>p.Contains(fileName)).OrderBy(p => Int32.Parse(p.Replace(fileName, "$").Split('$')[1])).ToArray();
            foreach (string filePath in filePaths)
            {
                MergeFiles(newPath, filePath);
            }
        }
        System.IO.File.Move(Path.Combine(tempPath, fileName),Path.Combine(videoPath,fileName));
        return "success";
    }

    private static void MergeFiles(string file1, string file2)
    {
        FileStream fs1 = null;
        FileStream fs2 = null;
        try
        {
            fs1 = System.IO.File.Open(file1, FileMode.Append);
            fs2 = System.IO.File.Open(file2, FileMode.Open);
            byte[] fs2Content = new byte[fs2.Length];
            fs2.Read(fs2Content, 0, (int) fs2.Length);
            fs1.Write(fs2Content, 0, (int) fs2.Length);
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message + " : " + ex.StackTrace);
        }
        finally
        {
            if (fs1 != null) fs1.Close();
            if (fs2 != null) fs2.Close();
            System.IO.File.Delete(file2);
        }
    }
}

However, if two users at same time upload files with same name, there will be some problem, and you have to handle this issue. By reading responseText, you can catch some error and exception and trim it.