Dear sir 
You are right but, I think Upload button not wrok.
I was test sample text
Could you help me , why upload button not work? 
public ContentResult SaveCapture(string data)
{
    //string fileName = DateTime.Now.ToString("dd-MM-yy hh-mm-ss");
    string fileNametest = DateTime.Now.ToString("deneme");
    string datats = "test";
    //byte[] imageBytes = Convert.FromBase64String(data.Split(',')[1]);
    // string filePath = Server.MapPath(string.Format("~/Captures/{0}.jpg", fileName));
    string filePathtest = Server.MapPath(string.Format("~/Captures/{0}.txt", fileNametest));
    System.IO.File.WriteAllText(filePathtest, datats);
    //System.IO.File.WriteAllBytes(filePath, imageBytes);
    return Content("true");
}
But there is no text file again
View is below like sample
@{
    Layout = null;
    ViewBag.Title = "Kamera Test 1.1";
}
<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <table border="0" cellpadding="0" cellspacing="0">
        <tr>
            <th align="center"><u>Live Camera</u></th>
            <th align="center"><u>Captured Picture</u></th>
        </tr>
        <tr>
            <td><div id="webcam"></div></td>
            <td><img id="imgCapture" /></td>
        </tr>
        <tr>
            <td align="center">
                <input type="button" id="btnCapture" value="Capture" />
            </td>
            <td align="center">
                <input type="button" id="btnUpload" value="Upload" disabled="disabled" />
            </td>
        </tr>
    </table>
    <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
    <script src="~/Webcam_Plugin/webcam.js"></script>
    <script type="text/javascript">
        $(function () {
            Webcam.set({
                width: 320,
                height: 240,
                image_format: 'jpeg',
                jpeg_quality: 90
            });
            Webcam.attach('#webcam');
            $("#btnCapture").click(function () {
                Webcam.snap(function (data_uri) {
                    $("#imgCapture")[0].src = data_uri;
                    $("#btnUpload").removeAttr("disabled");
                });
            });
            $("#btnUpload").click(function () {
                $.ajax({
                    type: "POST",
                    url: "/Home/SaveCapture",
                    data: "{data: '" + $("#imgCapture")[0].src + "'}",
                    contentType: "application/json; charset=utf-8",
                    dataType: "json",
                    success: function (r) { }
                });
            });
        });
    </script>
</body>
</html>
i was test on iphone safari