Round trip database reads becomes an issue with large databases. You may notice this occurs in grid views. Each time the dataset is sorted or filtered, the default grid view needs to be data binded. In most cases, the data source is the database (sql statement or stored procedure). An easy way to prevent these round trips across page loads is to use a session variable. One important aspect to note is that session variables expire by default after fifteen minutes.
We are going to store a Boolean variable rememberMe in a ViewState. By storing the Boolean in a ViewState, rememberMe will retain its value across page loads. In this example, the boolean variable rememberMe will default to false. The variable rememberMe can be read to and from as if any public class variable.
public partial class _Default : System.Web.UI.Page
{
public bool rememberMe
{
get
{
object o = ViewState["rememberMe "];
return (o == null)? false : (bool)o;
}
set
{
ViewState["rememberMe"] = value;
}
} protected void Page_Load(object sender, EventArgs e)
{
}
}
Again, it is important to note that session variables expire by default after fifteen minutes. If a default value is not assigned, additional logic is required to prevent unanticipated affects. This method is very effective when retrieving an extremely large number of records. You will immediately notice the first query will take the standard query time, but each subsequent action on the same dataset will be very quick.
To convert an exist ing aspx page without a masterpage site template is easy. We are going to walk through a simple example for which can be applied to other situations. Assume you have the following page called Default.aspx (with it’s associated Default.aspx.cs page which we will not need to worry about).
<%@ Page Language=”C#” AutoEventWireup=”true” CodeBehind=”Default.aspx.cs” Inherits=”WebApplication1._Default” %>
<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd”>
<html xmlns=”http://www.w3.org/1999/xhtml” >
<head runat=”server”>
<title>Hello World</title>
</head>
<body>
<form id=”form1″ runat=”server”>
<div>Hello World</div>
</form>
</body>
</html>
Now a standard masterpage with two content place holders (one for header information and the other for the main body content) is created for your web application called Site1.Master. Header and footer text has been added that will appear for every content item.
<%@ Master Language=”C#” AutoEventWireup=”true” CodeBehind=”Site1.master.cs” Inherits=”WebApplication1.Site1″ %> <!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd”> <html xmlns=”http://www.w3.org/1999/xhtml” >
<head runat=”server”>
<title>Untitled Page</title>
<asp:ContentPlaceHolder ID=”head” runat=”server”> </asp:ContentPlaceHolder>
</head>
<body>
Hello World Header!
<form id=”form1″ runat=”server”>
<div>
<asp:ContentPlaceHolder ID=”ContentPlaceHolder1″ runat=”server”> </asp:ContentPlaceHolder>
</div>
</form>
Hello World Footer!
</body>
</html>
First, an <%@ Page> tag is should be added to the first line. See resulting code for necessary tag attributes. Any page specific tags from the within the head tags except for <title> are placed inside the <asp:Content ID=”Content1″>. If there are no specific tags, this section will be present, but empty. Likewise, all content in the body (labeled in green in the above example), will be placed into <asp:Content ID=”Content2″>. To give your item template a title, there is a field in <%@ Page> called title which contains the page title (labeled in red in the above example). The final Default.aspx page will be as follows:
<%@ Page Language=”C#” MasterPageFile=”~/Site1.Master” AutoEventWireup=”true” CodeBehind=”Default.aspx.cs” Inherits=”WebApplication1.WebForm1″ Title=”Hello World” %>
<asp:Content ID=”Content1″ ContentPlaceHolderID=”head” runat=”server”>
</asp:Content>
<asp:Content ID=”Content2″ ContentPlaceHolderID=”ContentPlaceHolder1″ runat=”server”>Hello World
</asp:Content>
A regular webpage has now been converted to work with your defined masterpage! You can follow this as a basis to larger more complexed pages.