editing createuser Wizard in membership provider

<asp:CreateUserWizard ID="CreateUserWizard1" runat="server"
oncreateduser="CreateUserWizard1_CreatedUser1">
<wizardsteps>
<asp:CreateUserWizardStep runat="server">
<contenttemplate>
<table>
<tr>
<td align="center" colspan="2">
Sign Up for Your New Account</td>
</tr>
<tr>
<td align="right">
<asp:Label ID="UserNameLabel" runat="server" AssociatedControlID="UserName">User Name:
</td>
<td>
<asp:TextBox ID="TextBox1" runat="server">
<asp:RequiredFieldValidator ID="UserNameRequired" runat="server"
ControlToValidate="UserName" ErrorMessage="User Name is required."
ToolTip="User Name is required." ValidationGroup="CreateUserWizard1">*
</td>
</tr>
<tr>
<td align="right">
ValidationGroup="CreateUserWizard1">*



in the codebehind
...........Cmd.Parameters.AddWithValue("@username",textbox1.text)//error textbox.text does not exist in the current context