I am using TextBox to change the uploaded file name.
Please refer this code.
You need to type some name in TextBox before selecting the File.
HTML
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title>AsyncFileUpload Example</title>
<script type="text/javascript">
function uploadStarted() {
$get("imgDisplay").style.display = "none";
}
function uploadComplete(sender, args) {
var imgDisplay = $get("imgDisplay");
imgDisplay.src = "images/loader.gif";
imgDisplay.style.cssText = "";
var img = new Image();
img.onload = function () {
imgDisplay.style.cssText = "height:100px;width:100px";
imgDisplay.src = img.src;
};
img.src = "<%=ResolveUrl(UploadFolderPath) %>"
+ document.getElementById("<%=txtImageName.ClientID %>").value
+ args.get_fileName().substring(args.get_fileName().lastIndexOf(".")); ;
}
</script>
</head>
<body>
<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:TextBox ID="txtImageName" runat="server" />
<cc1:AsyncFileUpload OnClientUploadComplete="uploadComplete" runat="server" ID="AsyncFileUpload1"
Width="400px" UploaderStyle="Modern" CompleteBackColor="White" UploadingBackColor="#CCFFFF"
ThrobberID="imgLoader" OnUploadedComplete="FileUploadComplete" OnClientUploadStarted="uploadStarted" />
<asp:Image ID="imgLoader" runat="server" ImageUrl="~/images/loader.gif" /><br />
<br />
<img id="imgDisplay" alt="" src="" style="display: none" />
</form>
</body>
</html>
C#
protected string UploadFolderPath = "~/Uploads/";
protected void FileUploadComplete(object sender, EventArgs e)
{
if (AsyncFileUpload1.HasFile && !string.IsNullOrEmpty(txtImageName.Text.Trim()))
{
string filename = txtImageName.Text.Trim() + System.IO.Path.GetExtension(AsyncFileUpload1.FileName);
AsyncFileUpload1.SaveAs(Server.MapPath(this.UploadFolderPath) + filename);
}
}