Uploading file with Progress Bar

   <script language="javascript" type="text/javascript">

        var size = 2;

        var id = 0;

        function ProgressBar() {          

                document.getElementById("divProgress").style.display = "block";

                document.getElementById("divUpload").style.display = "block";

                id = setInterval("progress()", 20);

                return true;        

        }

        function progress() {

            size = size + 1;

            if (size > 299) {

                clearTimeout(id);

            }

            document.getElementById("divProgress").style.width = size + "pt";

            document.getElementById("<%=lblPercentage.ClientID %>").firstChild.data = parseInt(size / 3) + "%";

        }

    </script>

 <asp:Button ID="btnAddImage" runat="server" Text="Upload File"OnClientClick="return ProgressBar()" OnClick="btnAddImage_Click" />

<div id="divUpload" style="display: none">

                        <div style="width: 300pt; text-align: center;">

                            Uploading...</div>

                        <div style="width: 300pt; height: 20px; border: solid 1pt gray">

                            <div id="divProgress" runat="server" style="width: 1pt; height: 20px; background-color: Blue;

                                display: none">

                            </div>

                        </div>

                    </div>

Ref:

http://www.c-sharpcorner.com/uploadfile/rahul4_saxena/uploading-file-with-progress-bar/