Runat="server" does not exist in the current context

Question

I have a HiddenField1 that does not seem to exist when I run the C# code.

The error reads :

The name 'HiddenField1' does not exist in the current context.

HiddenField1 at line 54

Sorry, I don't know why the C# code comes out looking like that on the site.

public partial class Login : System.Web.UI.Page
{
    protected void LoginButton_Click1(object sender, EventArgs e)
    {
        string userName1 = Login1.UserName;
        string userPassword1 = Login1.Password;
        bool logSuccess = false;

        foreach (GridViewRow gvRow in GridView1.Rows)
        {

            if (userName1 == gvRow.Cells[1].Text && userPassword1 == gvRow.Cells[2].Text)
            {
                Response.Write("Logged in");
                logSuccess = true;
                break;
            }
        }
        if (logSuccess == true)
        { Response.Redirect("~/MemberPages/Members.aspx"); }
        else
        { HiddenField1.Value = ""; }
    }
}

<%@ Page Title="" Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true" CodeFile="Login.aspx.cs" Inherits="Login" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
    <style type="text/css">
        .auto-style4 {
            width: 158px;
        }
        .auto-style5 {
            height: 28px;
        }
        .auto-style6 {
            width: 158px;
            height: 28px;
        }
    </style>
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
    <h2>Login</h2>
    <p>
        <asp:Login ID="Login1" runat="server" Height="135px" Width="252px" OnAuthenticate="Login1_Authenticate">
            <LayoutTemplate>
                <table cellpadding="1" cellspacing="0" style="border-collapse:collapse;">
                    <tr>
                        <td>
                            <table cellpadding="0" style="height:135px;width:252px;">
                                <tr>
                                    <td align="center" colspan="2">Log In</td>
                                </tr>
                                <tr>
                                    <td align="right" class="auto-style5">
                                        <asp:Label ID="UserNameLabel" runat="server" AssociatedControlID="UserName">User Email:</asp:Label>
                                    </td>
                                    <td class="auto-style6">
                                        <asp:TextBox ID="UserName" runat="server"></asp:TextBox>
                                        <asp:RequiredFieldValidator ID="UserNameRequired" runat="server" ControlToValidate="UserName" ErrorMessage="User Name is required." ToolTip="User Name is required." ValidationGroup="Login1">*</asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                <tr>
                                    <td align="right">
                                        <asp:Label ID="PasswordLabel" runat="server" AssociatedControlID="Password">Password:</asp:Label>
                                    </td>
                                    <td class="auto-style4">
                                        <asp:TextBox ID="Password" runat="server" TextMode="Password"></asp:TextBox>
                                        <asp:RequiredFieldValidator ID="PasswordRequired" runat="server" ControlToValidate="Password" ErrorMessage="Password is required." ToolTip="Password is required." ValidationGroup="Login1">*</asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                <tr>
                                    <td colspan="2">
                                        <asp:CheckBox ID="RememberMe" runat="server" Text="Remember me next time." />
                                    </td>
                                </tr>
                                <tr>
                                    <td align="center" colspan="2" style="color:Red" >
                                       <asp:HiddenField ID="HiddenField1" Value="Invalid user email or password." runat="server"  />
                                       </td>
                                </tr>
                                <tr>
                                    <td align="right" colspan="2">
                                        <asp:Button ID="LoginButton" runat="server" CommandName="Login" Text="Log In" ValidationGroup="Login1" OnClick="LoginButton_Click1" />
                                    </td>
                                </tr>
                            </table>
                        </td>
                    </tr>
                </table>
            </LayoutTemplate>
        </asp:Login>
</p>
    <asp:ValidationSummary ID="ValidationSummary1" runat="server" 
        Group="Login1" />

<p>
    &nbsp;</p>
</asp:Content>

Answer 1

Because your HiddenField control is inside a LayoutTemplate you need to use the FindControl method to find it:

((HiddenField)Login1.FindControl("HiddenField1")).Value = "";