If More than one submit button inside the Asp.Net Panel,then we will write as:- <form id="frm" runat="server">
<asp:Panel ID="Panel1" runat="server" DefaultButton="btnPanel1">
<div>
<asp:TextBox ID="txtName" runat="server"></asp:TextBox>
<asp:TextBox ID="txtPwd" runat="server"></asp:TextBox>
<asp:Button ID="btnPanel1" runat="server" Text="Submit" OnClick="btnPanel1_Click" />
</div>
</asp:Panel>
<asp:Panel ID="Panel2" runat="server" DefaultButton="btnPanel2">
<div>
<asp:TextBox ID="txtEmpName" runat="server"></asp:TextBox>
<asp:TextBox ID="txtAge" runat="server"></asp:TextBox>
<asp:Button ID="btnPanel2" runat="server" Text="Submit" OnClick="btnPanel2_Click" />
</div>
</asp:Panel>
</form>