Hi telerik, 
I have a problem using the RadAjaxManager Control, I'm trying to load a combobox depending on the selected item in another combobox in a webform, but for do that the autopostback of the combobox has to be in true mode, so i add a RadAjaxManager so I would not reload the whole page, but it doesn't work.

I want to load the combobox cmbCuenta depending on the selected item in cmbBanco without reload the whole page. Thanks, for your help.

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" Runat="Server">
        <telerik:RadAjaxManager runat="server" ID="RadAjaxManager1" DefaultLoadingPanelID="RadAjaxLoadingPanel1">
            <AjaxSettings>
                <telerik:AjaxSetting AjaxControlID="cmbBanco">
                    <UpdatedControls>
                        <telerik:AjaxUpdatedControl ControlID="cmbCuenta" />
                    </UpdatedControls>
                </telerik:AjaxSetting>
                <telerik:AjaxSetting AjaxControlID="cmbCuenta">
                    <UpdatedControls>
                        <telerik:AjaxUpdatedControl ControlID="cmbChequera" />
                        <telerik:AjaxUpdatedControl ControlID="cmbMoneda" />
                    </UpdatedControls>
                </telerik:AjaxSetting>
                <telerik:AjaxSetting AjaxControlID="cmbTipoCuentaC">
                    <UpdatedControls>
                        <telerik:AjaxUpdatedControl ControlID="cmbCuentaContable" />
                    </UpdatedControls>
                </telerik:AjaxSetting>
            </AjaxSettings>
        </telerik:RadAjaxManager> 

 <telerik:RadAjaxLoadingPanel ID="RadAjaxLoadingPanel1" runat="server" Skin="Office2010Silver">
            <div class="loading">
            <asp:Image ID="Image1" runat="server" ImageUrl="~/Imagenes/loading1.gif" AlternateText="loading"></asp:Image>
            </div>
        </telerik:RadAjaxLoadingPanel>  

<table align="center" style="width: 98%">
                <tr>
                    <td class="auto-style4">
                        Banco:
                    </td>
                    <td colspan="2" class="auto-style4">
                        <telerik:RadComboBox ID="cmbBanco" runat="server" AutoPostBack="true" DataSourceID="SqlDataBanco" DataTextField="Nombre" DataValueField="IdBanco" EmptyMessage="Seleccione un Banco" OnSelectedIndexChanged="cmbBanco_SelectedIndexChanged">
                        </telerik:RadComboBox>
                    </td>
                </tr>
                <tr>
                    <td style="vertical-align: top; width: 20%" align="left" class="auto-style5">
                        <asp:Label ID="lblCuenta" runat="server" Text="Cuenta:"></asp:Label>
                    </td>
                    <td style="vertical-align: top; width: 30%" align="left">
                        <telerik:RadComboBox ID="cmbCuenta" Runat="server" Width="211px" AutoPostBack="true" OnSelectedIndexChanged="cmbCuenta_SelectedIndexChanged" EmptyMessage="Seleccione una Cuenta Bancaria">
                        </telerik:RadComboBox>
                    </td>
                    <td style="vertical-align: top; width: 20%" align="left" class="auto-style3">
                        <asp:Label ID="lblFecha" runat="server" Text="Fecha de emisión:"></asp:Label>
                    </td>
                    <td style="vertical-align: top; width: 30%" align="left" class="auto-style4">
                        <telerik:RadDatePicker ID="dttFechaEmision" runat="server">                            
                        </telerik:RadDatePicker>
                    </td>
                </tr>
            </table>
</asp:Content>

Hi Arnoldo,

The scenario like WebUserControls or Master/ContentPages try to set the RadAjaxManager instance on the main/master page and add a proxy to the usercontrol/content page. RadAjaxManagerProxy copies the exact same RadAjaxManager designer configuration so that you can set all the necessary AJAX settings within the WebUserControl/ContentPage entirely through the designer.  Please have a look into the following code snippet which works fine at my end.

ASPX:

<telerik:RadAjaxManager ID="RadAjaxManager1" runat="server" DefaultLoadingPanelID="RadAjaxLoadingPanel1">

</telerik:RadAjaxManager>

       
UserControlPage :

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">

    <telerik:RadAjaxManagerProxy ID="RadAjaxManagerProxy1" runat="server">

        <AjaxSettings>

            <telerik:AjaxSetting AjaxControlID="cmbBanco">

                <UpdatedControls>

                    <telerik:AjaxUpdatedControl ControlID="cmbCuenta" />

                </UpdatedControls>

            </telerik:AjaxSetting>

        </AjaxSettings>

    </telerik:RadAjaxManagerProxy>

    <telerik:RadAjaxLoadingPanel ID="RadAjaxLoadingPanel1" runat="server" Skin="Office2010Silver">

        <div class="loading">

            <asp:Image ID="Image1" runat="server" ImageUrl="~/Imagenes/loading1.gif" AlternateText="loading">

            </asp:Image>

        </div>

    </telerik:RadAjaxLoadingPanel>

    <table align="center" style="width: 98%">

        <tr>

            <td class="auto-style4">

                Banco:

            </td>

            <td colspan="2" class="auto-style4">

                <telerik:RadComboBox ID="cmbBanco" runat="server" AutoPostBack="true" DataSourceID="SqlDataSource1"

                    DataTextField="Countryname" DataValueField="Countryname" EmptyMessage="Seleccione un Banco"

                    OnSelectedIndexChanged="cmbBanco_SelectedIndexChanged">

                </telerik:RadComboBox>

            </td>

        </tr>

        <tr>

            <td style="vertical-align: top; width: 20%" align="left" class="auto-style5">

                <asp:Label ID="lblCuenta" runat="server" Text="Cuenta:"></asp:Label>

            </td>

            <td style="vertical-align: top; width: 30%" align="left">

                <telerik:RadComboBox ID="cmbCuenta" runat="server" Width="211px" AutoPostBack="true"

                    EmptyMessage="Seleccione una Cuenta Bancaria">

                </telerik:RadComboBox>

            </td>

            <td style="vertical-align: top; width: 20%" align="left" class="auto-style3">

                <asp:Label ID="lblFecha" runat="server" Text="Fecha de emisión:"></asp:Label>

            </td>

            <td style="vertical-align: top; width: 30%" align="left" class="auto-style4">

                <telerik:RadDatePicker ID="dttFechaEmision" runat="server">

                </telerik:RadDatePicker>

            </td>

        </tr>

    </table>

    <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString %>"

        SelectCommand="SELECT  [Countryname],  [Cityname] FROM [City]"></asp:SqlDataSource>

</asp:Content>

UserControlPage C#:

protected void cmbBanco_SelectedIndexChanged(object sender, Telerik.Web.UI.RadComboBoxSelectedIndexChangedEventArgs e)

{

    DataTable data = GetData(new SqlCommand("SELECT Cityname FROM City WHERE Countryname = '" + cmbBanco.SelectedItem.Text + "'"));

    cmbCuenta.DataTextField = "Cityname";

    cmbCuenta.DataSource = data;

    cmbCuenta.DataBind();

    cmbCuenta.SelectedIndex = 0;

}

private static DataTable GetData(SqlCommand selectCommand)

{

    selectCommand.Connection = new SqlConnection(ConfigurationManager.ConnectionStrings["NorthwindConnectionString"].ConnectionString);

    SqlDataAdapter adapter = new SqlDataAdapter(selectCommand);

    DataTable data = new DataTable();

    adapter.Fill(data);

    return data;

}

Hope this will helps you.
Thanks,
Shinu.

Thanks.
I'm sorry but the RadAjaxManager where it goes, in the principal page or inside the Content2?

Hi Arnoldo,

Please have a look into the following help documentation for RadAjaxManager and RadAjaxManagerProxy and a take a look on this online demo also. 

Hope this will helps you.
Thanks,
Shinu.