DefaultButton of 'panelName' must be the ID of a control of type IButtonControl

I am developing a website on ASP.NET and using bootstrap for the design. I'm using modal fade class (like a popup) for user to login.

Here's my code:

<div class="modal fade" id="login" role="dialog">
   <asp:Panel ID="AZloginPanel" runat="server">
      <div class="modal-dialog">
         <div class="modal-content">
            <div class="form-horizontal">
               <div class="modal-header">
                  <h4>Login</h4>
               </div>
            <div class="modal-body">
               <asp:Login ID="LoginUser" runat="server" EnableViewState="false" RenderOuterTable="false">
                  <LayoutTemplate>
                     <span class="failureNotification">
                        <asp:Literal ID="FailureText" runat="server"></asp:Literal>
                     </span>
                     <asp:ValidationSummary ID="LoginUserValidationSummary" runat="server" CssClass="failureNotification"
                                        ValidationGroup="LoginUserValidationGroup" />
                     <div class="accountInfo">
                        <fieldset class="login">
                           <div class="form-group">
                              <asp:Label ID="UserNameLabel" CssClass="col-lg-2 control-label" runat="server" AssociatedControlID="UserName">Username:</asp:Label>
                                <div class="col-lg-10">
                                   <asp:TextBox ID="UserName" runat="server" CssClass="form-control" placeholder="Username"></asp:TextBox>
                                </div>
                                <asp:RequiredFieldValidator ID="UserNameRequired" runat="server" ControlToValidate="UserName"
                                                    CssClass="failureNotification" ErrorMessage="User Name is required." ToolTip="User Name is required."
                                                    ValidationGroup="LoginUserValidationGroup">*</asp:RequiredFieldValidator>
                           </div>
                           <div class="form-group">
                              <asp:Label ID="PasswordLabel" CssClass="col-lg-2 control-label" runat="server" AssociatedControlID="Password">Password:</asp:Label>
                              <div class="col-lg-10">
                                 <asp:TextBox ID="Password" runat="server" CssClass="form-control" placeholder="Password" TextMode="Password"></asp:TextBox>
                              </div>
                              <asp:RequiredFieldValidator ID="PasswordRequired" runat="server" ControlToValidate="Password"
                                                    CssClass="failureNotification" ErrorMessage="Password is required." ToolTip="Password is required."
                                                    ValidationGroup="LoginUserValidationGroup">*</asp:RequiredFieldValidator>
                           </div>
                           <p>
                              <asp:CheckBox ID="RememberMe" runat="server" />
                              <asp:Label ID="RememberMeLabel" runat="server" AssociatedControlID="RememberMe" CssClass="inline">Keep me logged in</asp:Label>
                           </p>
                        </fieldset>
                        <div class="modal-footer">
                           <p class="pull-left">
                                <asp:HyperLink ID="RegisterHyperLink" runat="server" EnableViewState="false" NavigateUrl="~/Account/Register.aspx">Register</asp:HyperLink>if you don't have an account.
                           </p>
                              <asp:Button ID="CloseModal" runat="server" CssClass="btn btn-info" CommandName="Close" Text="Close" />
                              <asp:Button ID="LoginButton" runat="server" CssClass="btn btn-primary" CommandName="Login" Text="Log In" ValidationGroup="LoginUserValidationGroup" />
                         </div>
                     </div>
                  </LayoutTemplate>
               </asp:Login>
            </div>
         </div>
      </div>
   </div>
</asp:Panel>
</div>

When I set DefaultButton="LoginButton" in AZloginPanel panel, I get the following error:

The DefaultButton of 'AZloginPanel' must be the ID of a control of type IButtonControl.

I'm lost and I've tried everything but it seems I'm at dead end.

Any ideas?

The problem is that the asp:login control modifies the id's of it's children, so the asp:panel control does not know where to look to find the new DefaultButton id.

Here's a simplified version that reproduces the issue:

<!-- language: lang-html --> <pre><code>&lt;asp:Panel ID=&quot;AZloginPanel&quot; runat=&quot;server&quot; <b>DefaultButton=&quot;LoginButton&quot;</b>&gt; &lt;asp:Login ID=&quot;LoginUser&quot; runat=&quot;server&quot; &gt; &lt;LayoutTemplate&gt; &lt;asp:TextBox ID=&quot;UserName&quot; runat=&quot;server&quot; /&gt; &lt;asp:TextBox ID=&quot;Password&quot; runat=&quot;server&quot; TextMode=&quot;Password&quot; /&gt; &lt;asp:Button ID=&quot;LoginButton&quot; runat=&quot;server&quot; Text=&quot;Log In&quot; /&gt; &lt;/LayoutTemplate&gt; &lt;/asp:Login&gt; &lt;/asp:Panel&gt; </code></pre>

If you want to use a DefaultButton for a LoginControl, you can do one of two things:

1. Nest the panel inside of the login control:

<pre><code>&lt;asp:Login ID=&quot;LoginUser&quot; runat=&quot;server&quot; &gt; &lt;LayoutTemplate&gt; <b>&lt;asp:Panel runat=&quot;server&quot; DefaultButton=&quot;LoginButton&quot;&gt;</b> &lt;asp:TextBox ID=&quot;UserName&quot; runat=&quot;server&quot; /&gt; &lt;asp:TextBox ID=&quot;Password&quot; runat=&quot;server&quot; TextMode=&quot;Password&quot; /&gt; &lt;asp:Button ID=&quot;LoginButton&quot; runat=&quot;server&quot; Text=&quot;Log In&quot; /&gt; <b>&lt;/asp:Panel&gt;</b> &lt;/LayoutTemplate&gt; &lt;/asp:Login&gt; </code></pre>

2. Build the ID with the LoginControlID then $ then Button ID:

<pre><code>&lt;asp:Panel ID=&quot;AZloginPnl&quot; runat=&quot;server&quot; <b>DefaultButton=&quot;LoginUser$LoginButton&quot;</b>&gt; &lt;asp:Login ID=&quot;<b>LoginUser</b>&quot; runat=&quot;server&quot; &gt; &lt;LayoutTemplate&gt; &lt;asp:TextBox ID=&quot;UserName&quot; runat=&quot;server&quot; /&gt; &lt;asp:TextBox ID=&quot;Password&quot; runat=&quot;server&quot; TextMode=&quot;Password&quot; /&gt; &lt;asp:Button ID=&quot;<b>LoginButton</b>&quot; runat=&quot;server&quot; Text=&quot;Log In&quot; /&gt; &lt;/LayoutTemplate&gt; &lt;/asp:Login&gt; &lt;/asp:Panel&gt; </code></pre>