why it says there are not my text boxes - asp.net

Question

i wrote below code . but i do not know why i get error. but every thing seems ok.
it says there are not my text boxes in context. but there are .
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
<form id="form1" runat="server">
<asp:TextBox ID="address" runat="server"/>
<div class="form1">
<label for="fname">
<span>name:</span>
<asp:TextBox ID="fname" runat="server"/>
</label>
<label for="lname">
<span>lname: </span>
<asp:TextBox ID="lname" name="lname" runat="server" />
</label>
.
.
.
</div>
protected void send2_Click(object sender, EventArgs e)
{
tbl_register tbl = new tbl_register();
tbl.firstname = fname.Text; // The name 'fname' does not exist in the current context
tbl.lastname = lname.Text; // The name 'lname'does not exist in the current context
tbl.address = address1.Text; //..
tbl.phone = phone.Text; //..
tbl.email = email3.Text; //..
db.tbl_registers.InsertOnSubmit(tbl);
db.SubmitChanges();
}

Answer 1

The textboxes as coded are children of the label. I do not code my lables in that way. In order to use controls that are child controls you must use Control.FindControl, in this case fname.FindControl("fname"). I would not name controls the same as other controls. You can also close the label tag such that it does not enclose those controls, and then the control can be referenced via the name.

Answer 2

the line
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
suggests that this is a webform that uses a MasterPage.
inside the content place holder you have a form declaration that runs at server:
<form id="form1" runat="server">
however, on your MasterPage.master you already have a form that runs at server that wraps the content placeholder.
asp.net does not allow 2 nested forms to both run at server.