Hi,
How you didn't post the code and i could not create the error.
I will write all the elements necessary for you create a master page.
Your master page
1 -
Scriptmanager component is obrigatory.
<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
2 - Updatepanel need to
ContentTemplate tag.
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
</ContentTemplate>
</asp:UpdatePanel>
3 - Verify if the namespace is equal in the html and code-behind.
<%@ Master Language="C#" AutoEventWireup="true" CodeBehind="Site1.master.cs" Inherits="aplicacao.Site1" %>
namespace aplicacao {}
Child Page
1 - Add tag master page in child page html.
<%@ Page Language="C#" AutoEventWireup="true" MasterPageFile="~/Site1.Master" CodeBehind="frmMyTest7.aspx.cs" Inherits="aplicacao.frmMyTest7" %>
<%@ MasterType VirtualPath="~/Site1.Master" %>
2 -
Content tag in child page is obrigatory.
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
</asp:Content>
Below is the complete code to help you.
Master Page
HTML
<body>
<form id="form1" runat="server">
<div>
<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:TextBox runat="server"></asp:TextBox>
<asp:Calendar runat="server"></asp:Calendar>
<asp:ContentPlaceHolder ID="ContentPlaceHolder1" runat="server">
</asp:ContentPlaceHolder>
</ContentTemplate>
</asp:UpdatePanel>
</div>
</form>
</body>
Code-behind
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace aplicacao
{
public partial class Site1 : System.Web.UI.MasterPage
{
protected void Page_Load(object sender, EventArgs e)
{
}
}
}
Child Page
HTML
<%@ Page Language="C#" AutoEventWireup="true" MasterPageFile="~/Site1.Master" CodeBehind="frmMyTest7.aspx.cs" Inherits="aplicacao.frmMyTest7" %>
<%@ MasterType VirtualPath="~/Site1.Master" %>
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
</asp:Content>
Code-behind
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace aplicacao
{
public partial class frmMyTest7 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
}
}