Hi nauna,

Use OnClientUploadCompleteAll event.

Check this example. Now please take its reference and correct your code.

HTML

<form id="form1" runat="server">
    <asp:ToolkitScriptManager runat="server">
    </asp:ToolkitScriptManager>
    <asp:AjaxFileUpload ID="AjaxFileUpload11" runat="server" MaximumNumberOfFiles="5" Width="400px" 
        OnUploadComplete="OnUploadComplete" OnClientUploadCompleteAll="ClientUploadCompleteAll" />
</form>
<script type="text/javascript">
    function ClientUploadCompleteAll(sender) {
        window.location = window.location.href;
    }
</script>

Code

C#

protected void OnUploadComplete(object sender, AjaxControlToolkit.AjaxFileUploadEventArgs e)
{
    string fileName = System.IO.Path.GetFileName(e.FileName);
    AjaxFileUpload11.SaveAs(Server.MapPath("~/Uploads/" + fileName));
}

VB.Net

Protected Sub OnUploadComplete(sender As Object, e As AjaxControlToolkit.AjaxFileUploadEventArgs)
    Dim fileName As String = IO.Path.GetFileName(e.FileName)
    AjaxFileUpload11.SaveAs(Server.MapPath(Convert.ToString("~/Uploads/") & fileName))
End Sub

Screenshot