Une seule instance d'un ScriptManager peut être ajouté à la page asp.net

Lorsque j'essaie d'ajouter un contrôle utilisateur, j'ai eu cette erreur

Only one instance of a ScriptManager can be added to the page 

Code:

.ascx

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="VisaUserControl.ascx.cs" Inherits="Portal.VisaUserControl" %>
<%@ Register Assembly="BasicFrame.WebControls.BasicDatePicker" Namespace="BasicFrame.WebControls" TagPrefix="dp" %>
<asp:ScriptManager ID="scriptmanager1" runat="server"></asp:ScriptManager>
<div id="divreg" runat="server">
<table id="tbl" runat="server">
<tr>
<td>
<asp:Label ID="lbl2" runat="server"></asp:Label>
</td>
</tr>
<tr>
<td> Visa Number:</td>
<td><asp:TextBox ID="txtUser" Width="160px" runat="server"/></td>
<td> Country Name:</td>
<td><asp:DropDownList ID="dropCountry" Width="165px" runat="server"></asp:DropDownList></td>
</tr>
<tr>
<td> Type of Visa:</td>
<td><asp:DropDownList ID="dropVisa" Width="165px" runat="server" OnSelectedIndexChanged="dropVisa_SelectedIndexChanged"></asp:DropDownList></td>
<td> Type of Entry:</td>
<td><asp:DropDownList ID="dropEntry" Width="165px" runat="server"></asp:DropDownList></td>
</tr>
<tr>
<td> Expiry Date</td>
<td><asp:TextBox ID="txtDate" runat="server"></asp:TextBox>
<ajaxToolkit:CalendarExtender ID="CalendarExtender1" runat="server" 
TargetControlID="txtDate" PopupButtonID="Imgbtnfromdate" Format="dd/MM/yyyy">
</ajaxToolkit:CalendarExtender>
</td>
<td>
<asp:Button ID="btnRemove" Text="Remove" runat="server" OnClick="btnRemove_Click" />
</td>
</tr>
</table>
</div>

.aspx.cs

  protected override void LoadViewState(object savedState)
{
base.LoadViewState(savedState);
GenerateControls();
}
private void GenerateControls()
{
foreach (string i in NoOfControls)
{
VisaUserControl ctrl = (VisaUserControl)Page.LoadControl("VisaUserControl.ascx");
ctrl.ID = i;
this.rpt1.Controls.Add(ctrl);
}
}

Ici, est le problème

    protected void btnAddVisa_Click(object sender, EventArgs e)
{
List<string> temp = null;
var uc = (VisaUserControl)this.LoadControl(@"VisaUserControl.ascx");
string id = Guid.NewGuid().ToString();
uc.ID = id;
temp = NoOfControls;
temp.Add(id);
NoOfControls = temp;
rpt1.Controls.Add(uc);
}

Dans l'image ci-dessous si Cliquer sur le bouton ajouter j'ai eu cette erreur

Des idées? Merci d'avance

OriginalL'auteur user2500094 | 2013-09-30