if condition is right then goes to next page in asp.net

Question

hi experts...

 

my scenario is when user enter its right answer then it goes to next page otherwise shows an error "incorrect error"

<table>
<tr>
<td>Security Question1</td>
<td>
<asp:DropDownList ID="ddlQuestion" runat="server" AppendDataBoundItems="true">
</asp:DropDownList>
<asp:TextBox ID="TxtAnswer" runat="server"></asp:TextBox>
</td>
</tr>
<tr>
<td>
<asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="btnSubmit_Click" />
</td>
</tr>
<tr>
<td>
<asp:Label ID="lblerror" runat="server"></asp:Label>
</td>
</tr>
</table>

protected void btnSubmit_Click(object sender, EventArgs e)
{
using (var context = new schoolEntities6())
{
string username = Request.QueryString["username"];
var user = (from c in context.SecurityQuestions
where c.SecQue == ddlQuestion.SelectedItem.Value
select c).FirstOrDefault();
if (user != null)
{
schoolEntities6 db = new schoolEntities6();
Session["UserName"] = username;
Response.Redirect("/ChangePassword.aspx?username=" + username);
}
else
{
lblerror.Text = "incorrect answer";
}
}
}

I am using this way to execute but doesn't work...