I need to make the user select a checkbox before I let them log in.  Sounds simple right.  but I am doing something wrong.  here is my code that always returns null for the controls.  Any help would be greatly appreciated.  I have tried this code in the page load, and prerender of the login control.

//Get the Check Box
        CheckBox cb = (CheckBox)MasterLoginView.FindControl("ValidateCheckBox") as CheckBox;
       
        // Check to make sure the check box is there.
        if (cb != null)
        {
            // Get the login button. Button btn = (Button)MasterLoginView.FindControl("LoginButton") as Button;
           
            // Check to make sure the button is there.
            if (btn != null)
            {
                // if the checkbox is checked then enable the button.
                btn.Enabled = cb.Checked;               
            }
        }

How about doing something like this?

ASPX 

<asp:loginview id="LoginView1" runat="server">
	<anonymoustemplate>
		<asp:checkbox id="chkConfirm" runat="server" autopostback="true" oncheckedchanged="chkConfirm_CheckedChanged"
			text="You must check this box before logging in" /><br />
		<br />
		<asp:button id="btnLogin" runat="server" enabled="false" text="Login" />
	</anonymoustemplate>
</asp:loginview>

CODE-BEHIND 

protected void chkConfirm_CheckedChanged(object sender, EventArgs e)
{
	// Retrieve controls
	CheckBox chkConfirm = sender as CheckBox;
	Button btnLogin = LoginView1.FindControl("btnLogin") as Button;

	if (btnLogin != null)
	{
		btnLogin.Enabled = chkConfirm.Checked;
	}
}

Almost works for me

Thanks.  that resolved half my problem! 

I am still getting a null for the login button.  By accessing the check box through the sender I can reference it.  But I am still a no go on the button.

 Here is the code for accessing the button.

Button btn = MasterLoginView.FindControl("LoginButton") as Button; 

I have checked the spelling several times and even copied the ID value from the control into the code so I  know the spelling is correct. 

That is the crazy part.  I am not.   Below is my code behind and the script.  I just know I have missed something incredibly stupid because rocket science this is not!

 thanks for taking the time to help me with this.

<asp:LoginView ID="MasterLoginView" runat="server">
            <LoggedInTemplate>
                 <br />
                <br />
                <br />
                <br />
                <br />
                <br />
                Welcome Back
                <asp:LoginName ID="LoginName1" runat="server" />
                <br />
                <br />
                <br />
                <br />
                <br />
                <br />
                <br />
                <br />
                <br />
                <br />
                <br />
            </LoggedInTemplate>
            <AnonymousTemplate>
                <asp:Login ID="Login1" runat="server" BackColor="#F7F7DE" BorderColor="#CCCC99" BorderStyle="Solid"
                    BorderWidth="1px" Font-Names="Verdana" Font-Size="10pt" Orientation="Horizontal"
                    PasswordRecoveryText="Forgot your Password?" PasswordRecoveryUrl="~/USER/RecoverPassword.aspx">
                    <TitleTextStyle BackColor="#6B696B" Font-Bold="True" ForeColor="White" />
                    <LayoutTemplate>
                        <table id="TABLE1" border="0" cellpadding="1" cellspacing="0" style="border-collapse: collapse"
                            onclick="return TABLE1_onclick()">
                            <tr>
                                <td>
                                    <table border="0" cellpadding="0">
                                        <tr>
                                            <td align="center" colspan="6" style="font-weight: bold; color: white; background-color: #6b696b">
                                                Log In</td>
                                        </tr>
                                        <tr>
                                            <td>
                                                <asp:Label ID="UserNameLabel" runat="server" AssociatedControlID="UserName">User Name:</asp:Label></td>
                                            <td>
                                                <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="ctl00$Login1">*</asp:RequiredFieldValidator>
                                            </td>
                                            <td>
                                                <asp:Label ID="PasswordLabel" runat="server" AssociatedControlID="Password">Password:</asp:Label></td>
                                            <td>
                                                <asp:TextBox ID="Password" runat="server" TextMode="Password"></asp:TextBox>
                                                <asp:RequiredFieldValidator ID="PasswordRequired" runat="server" ControlToValidate="Password"
                                                    ErrorMessage="Password is required." ToolTip="Password is required." ValidationGroup="ctl00$Login1">*</asp:RequiredFieldValidator>
                                            </td>
                                            <td>
                                                <asp:CheckBox ID="RememberMe" runat="server" Text="Remember me next time." />
                                            </td>
                                            <td>
                                                <asp:Button ID="LoginButton" runat="server" CommandName="Login" Text="Log In" ValidationGroup="ctl00$Login1" />
                                            </td>
                                        </tr>
                                        <tr>
                                            <td colspan="6" style="color: red">
                                                <asp:Literal ID="FailureText" runat="server" EnableViewState="False"></asp:Literal>
                                            </td>
                                        </tr>
                                        <tr>
                                            <td colspan="6">
                                                <asp:HyperLink ID="PasswordRecoveryLink" runat="server" NavigateUrl="~/USER/RecoverPassword.aspx">Forgot your Password?</asp:HyperLink>
                                            </td>
                                        </tr>
                                    </table>
                                    <asp:CheckBox ID="ValidateCheckBox" runat="server" AutoPostBack="True" Text="By selecting this check box you are acknowledging that the account you are using to log into this system was issued to you."
                                        TextAlign="Left" OnCheckedChanged="ValidateCheckBox_CheckedChanged" Visible="False" /></td>
                            </tr>
                        </table>
                    </LayoutTemplate>
                </asp:Login>
            </AnonymousTemplate>
        </asp:LoginView>

protected void ValidateCheckBox_CheckedChanged(object sender, EventArgs e)
    {
        CheckBox cb = sender as CheckBox;
        // Check to make sure the check box is there.
        if (cb != null)
        {
            // Get the login button.
            Button btn = MasterLoginView.FindControl("LoginButton") as Button;

            // Check to make sure the button is there.
            if (btn != null)
            {
                // if the checkbox is checked then enable the button.
                btn.Enabled = cb.Checked;
            }
        }
    }    

I do not know why but if you have a LoginView the FindControl will not work.

If you do:

MasterLoginView.Controls[0].FindControl("LoginButton");

it will work.

-Luis 

Your problem is that your attempting to find a control within a template within a template. Therefore, you need to find the Login control first, then find the Button like so:

ASPX 

<asp:loginview id="LoginView1" runat="server">
	<anonymoustemplate>
		<asp:login id="Login1" runat="server">
			<layouttemplate>
				<table border="0" cellpadding="1" cellspacing="0" style="border-collapse: collapse">
					<tr>
						<td>
							<table border="0" cellpadding="0">
								<tr>
									<td align="center" colspan="2">
										Log In</td>
								</tr>
								<tr>
									<td align="right">
										<asp:label id="UserNameLabel" runat="server" associatedcontrolid="UserName">User Name:</asp:label></td>
									<td>
										<asp:textbox id="UserName" runat="server" />
										<asp:requiredfieldvalidator id="UserNameRequired" runat="server" controltovalidate="UserName"
											errormessage="User Name is required." tooltip="User Name is required." validationgroup="ctl00$Login1">*</asp:requiredfieldvalidator>
									</td>
								</tr>
								<tr>
									<td align="right">
										<asp:label id="PasswordLabel" runat="server" associatedcontrolid="Password">Password:</asp:label></td>
									<td>
										<asp:textbox id="Password" runat="server" textmode="Password" />
										<asp:requiredfieldvalidator id="PasswordRequired" runat="server" controltovalidate="Password"
											errormessage="Password is required." tooltip="Password is required." validationgroup="ctl00$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:literal id="FailureText" runat="server" enableviewstate="False" />
									</td>
								</tr>
								<tr>
									<td align="right" colspan="2">
										<asp:button id="LoginButton" runat="server" commandname="Login" enabled="False" text="Log In"
											validationgroup="ctl00$Login1" />
									</td>
								</tr>
							</table>
							<asp:checkbox id="ValidateCheckBox" runat="server" autopostback="True" oncheckedchanged="ValidateCheckBox_CheckedChanged"
								text="By selecting this check box you are acknowledging that the account you are using to log into this system was issued to you." />
						</td>
					</tr>
				</table>
			</layouttemplate>
		</asp:login>
	</anonymoustemplate>
</asp:loginview>

CODE-BEHIND 

protected void ValidateCheckBox_CheckedChanged(object sender, EventArgs e)
{
	// Retrieve controls
	CheckBox chk = sender as CheckBox;
	Login log = LoginView1.FindControl("Login1") as Login;

	if (log != null)
	{
		Button btn = log.FindControl("LoginButton") as Button;

		if (btn != null)
		{
			btn.Enabled = chk.Checked;
		}
	}
}