How to show a label during button click processing?

Is there any way to show label that shows "uploading.." while my button click is processing?

I am doing it in this way

protected void btnUpload_Click(object sender, EventArgs e)
{
    lblOutput.Text="uploading..";

    HttpPostedFile postedFile = FileUpload1.PostedFile;
    string ClientFileName, ServerFileName;

    if ((FileUpload1.HasFile && FileUpload1.PostedFile != null) || txtUrl.Text!="")
    {
        try
        {
            HttpPostedFile myFile = FileUpload1.PostedFile;

            if (fileType == "Image")
            {
                if (fileExt == ".jpg" || fileExt == ".gif" || fileExt == ".png" || 
                    fileExt == ".bmp" || fileExt == ".tif")
                {
                    ServerFileName = System.IO.Path.Combine(ServerSavePathI, ClientFileName);
                    string serverPath = Server.MapPath(ServerFileName);
                    FileUpload1.SaveAs(serverPath);
                    dbInsert(fileType, fileName, fileExt, 
                             filePath+fileType+"/"+fileN开发者_运维百科ame.Replace(" ",string.Empty)+fileExt, 
                             url);
                }
            }
        }
    }
}

But it showed after my file has been uploaded already.

Am I doing something wrong, or is there any other way to do this?

---

<script type="text/javascript">
        function showMessage() {
            document.getElementById("<%= lblOutput.ClientID %>").innerHTML = "uploading..";
        }
    </script>

<asp:FileUpload runat="server" ID="FileUpload1" />
    <asp:Button runat="server" ID="btnUpload" Text="Upload" OnClick="btnUpload_Click" OnClientClick="showMessage()" />
    <asp:Label runat="server" ID="lblOutput" />

---

The priority of showing the lable's text is lower than the upload thread.You can solve this by use another thread to handle the text change event.Hope helps.