the file upload one line code is working but when i integrate it in the web application it doesn`t work

**.aspx**
<div class="form-group" style="padding: 10px; text-align: right;">
                                        <label for="client_tax_photo_numInput1">صورة البطاقة الضريبية</label>
                                        <asp:FileUpload runat="server" ID="client_tax_photo" />
                                    </div>

**.aspx.cs**
protected void Add_Ticket_Click(object sender, EventArgs e){
addnewclient();
addnewticket();
}

void addnewclient() {
client_tax_photo.SaveAs(Server.MapPath("../docs") + "//" + client_tax_photo.FileName);
 }

void addnewticket() { }

i created a page to test the file upload to make sure its not permissions issue and its working.

would you please tell me what is wrong