default.aspx :
   <asp:Button Text="Submit" runat="server" OnClick="RegisterUser"  postbackurl="userinfo.aspx"/>

default.aspx.cs :
    private void Button1_Click(object sender, System.EventArgs e)
    {
        Session["username"] = txtUsername.Text;
        Response.Redirect("userinfo.aspx", false);

    }



userinfo.aspx.cs :
string a = Session["username"].ToString();
scmd.CommandText = "SELECT * FROM registered where username = @a";