File extension validation in AsyncFileUpload Control on server side (code behind) in ASP.Net

Hi rakeshkuma,

If you want to display any information using OnUploadedComplete from server side, its not possible.

One work around is that you use ScriptManager RegisterClientScriptBlock().

Refer below code.

HTML

<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<ajax:AsyncFileUpload ID="AsyncFileUpload1" CssClass="form-control" CompleteBackColor="White"
    Width="100%" runat="server" UploaderStyle="Modern" UploadingBackColor="White" ThrobberID="imgLoad"
    OnUploadedComplete="AsyncFileUpload1_UploadedComplete" />
<asp:Image ID="imgLoad" runat="server" ImageUrl="~/images/loader.gif" />
<asp:Label ID="Label38" runat="server" Font-Size="12px" ForeColor="Green"></asp:Label>
<asp:Label ID="Label39" runat="server" Font-Size="12px" ForeColor="Red"></asp:Label>

Code

C#

protected void AsyncFileUpload1_UploadedComplete(object sender, AsyncFileUploadEventArgs e)
{
    string extension = Path.GetExtension(e.filename);
    if (extension.ToLower() == ".pdf")
    {
        AsyncFileUpload1.SaveAs(Server.MapPath("documents/") + Path.GetFileName(e.filename));
        ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "success", 
            "top.$get(\"" + Label38.ClientID + "\").innerHTML ='Upload done !!';", true);
    }
    else
    {
        ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "error", 
            "top.$get('" + Label39.ClientID + "').innerHTML ='Upload only .pdf file !!';", true);
    }
}

VB.Net

Protected Sub AsyncFileUpload1_UploadedComplete(ByVal sender As Object, ByVal e As AsyncFileUploadEventArgs)
    Dim extension As String = Path.GetExtension(e.filename)
    If extension.ToLower() = ".pdf" Then
        AsyncFileUpload1.SaveAs(Server.MapPath("documents/") + Path.GetFileName(e.filename))
        ScriptManager.RegisterClientScriptBlock(Me, Me.GetType(), "success", _
                                                "top.$get(""" & Label38.ClientID & """).innerHTML ='Upload done !!';", True)
    Else
        ScriptManager.RegisterClientScriptBlock(Me, Me.GetType(), "error", _
                                                "top.$get('" & Label39.ClientID & "').innerHTML ='Upload only .pdf file !!';", True)
    End If
End Sub