Reducing the size of ASP.NET pages

Introduction

We all know when a page is requested, ASP.NET processes the page, its server controls, and finally sends the HTML to the client-side for the browser to render it. The time taken to download the HTML at the client side depends mainly on the final size of the page. If your page is data rich, it would take a lot of time to fetch it. So here I am presenting a technique to reduce the size of ASP.NET web pages.

Background

When you see a page's HTML source by clicking “View Source” in the browser, you could see that there are a lot of white space on the left side of each line on the HTML. This is actually a waste. Try saving the HTML page to your desktop and notice its size. Then delete all the spaces on the left side and then check its size. You could see that the size of the page reduces considerably, sometimes more than 50%!! (watch the View Source of Orkut in a browser).

Using the code

Here is a technique to achieve the same.

1. Create a class in App_Code that derives from the System.Web.UI.Page class.

public class MyPageBase : System.Web.UI.Page
{
}

2. Replace System.Web.UI.Page in all your web pages (.aspx.cs) with MyPageBase. This means that now all your web pages are deriving from MyPageBase.
3. Override the Render function in this class:

public class MyPageBase : System.Web.UI.Page
{
    protected override void Render(HtmlTextWriter writer)
    {
    }
}

4. Place the code below inside the function, and also write a support function as shown below:

public class MyPageBase : System.Web.UI.Page
{
    protected override void Render(HtmlTextWriter writer)
    {
            base.Render(htmlwriter);
            string html = htmlwriter.InnerWriter.ToString().Trim();

            if (ConfigurationManager.AppSettings["OptimizeHtmlOutput"] != "0")
            {
                bool isAsync = !html.StartsWith("<");

                if (!isAsync)
                {
                    StringBuilder sb = MyPageBase._TrimHtml(html);
                    writer.Write(sb.ToString());
                }
                else
                {
                    StringBuilder sb = new StringBuilder();

                    int startIx = 0;
                    while (true)
                    {
                        int x = html.IndexOf("|updatePanel|", startIx);

                        if (x > -1)
                        {
                            int xS = html.LastIndexOf("\r\n", x);
                            xS = (xS < 0 ? 0 : xS);
                            int xE = html.IndexOf("\r\n", x) + 2;

                            string header = html.Substring(xS, xE - xS);
                            header = header.Trim().TrimStart('|', ' ');

                            string sLen = header.Substring(0, header.IndexOf('|'));
                            int cLen = int.Parse(sLen);

                            string content = html.Substring(xE - 2, cLen);
                            content = MyPageBase._TrimHtml(content).ToString().Trim();

                            startIx = xE - 2 + cLen;

                            cLen = content.Length + 4;
                            header = (xS > 0 ? "|" : string.Empty) + 
                                      cLen.ToString() + 
                                      header.Substring(header.IndexOf('|'));

                            sb.AppendLine(header);
                            sb.AppendLine(content);
                        }
                        else
                        {
                            string stateData = html.Substring(startIx);
                            sb.Append(stateData.Trim());

                            writer.Write(sb.ToString());
                            break;
                        }
                    }
                }
            }
            else
            {
                writer.Write(html);
            }
        }
    }

    private static StringBuilder _TrimHtml(string source)
    {
        StringBuilder sb = new StringBuilder();

        source = source.Trim();
        using (StringReader sr = new StringReader(source))
        {
            string data = string.Empty;
            while (data != null)
            {
                data = sr.ReadLine();
                if (data != null)
                {
                    data = data.TrimStart(' ', '\t');
                    if (data != string.Empty) sb.AppendLine(data);
                }
            }
        }

        return sb;
    }
} 

Notes

1. Notice the usage of ConfigurationManager.AppSettings["OptimizeHtmlOutput"] != "0". You can define a key in the appsettings section of the web.config file to enable or disable this feature. Any value other than “0” will enable optimization.
2. This code works well in AJAX based applications as well. Compare the size difference and performance by changing the flag. This is very beneficial especially in pages which contain a huge amount of data.