Readonly Vs Constant Variables in .Net

ReadOnly variable can be declared without assigning a value to it.
Constant variable can only be declared with assigning a value to it.

ReadOnly variable can be assigned in constructor or in object intialization.
Constant are same, cannot be modified anytime.

js File Compressor for ASP.Net applications

Create a WebSite, or Add a reference of the dll to the WebSite.

In Web.Config file a new httpHandler in HttpHandlers Section.

<add path="*.js"
type="ClassLibrary1.Handler, ClassLibrary1, Version=, Culture=neutral"
validate="false" verb="*">

That's all, rest of the work will be done by our Handler.
Let us see how it works,

Basically the HttpHandlers are used to handle the request of the WebApplication.
This Handler is to handle the javascript file. it removes the white spaces, new line characters, inline comments and multiline comments. the Handlers class is inherited from the IHttpHandler Interface, it implements ProcessRequest method.

//Getting the script file name from request
Uri url = context.Request.Url;
string filename = url.Segments[url.Segments.Length-1];

//Creating a file stream to read the script file.
FileStream fs = new FileStream(context.Server.MapPath(filename), FileMode.Open);
StreamReader sr = new StreamReader(fs);
string js = sr.ReadToEnd();
string a = string.Empty , b = string.Empty;
//Removing the single line comments
while (js.IndexOf("//")!=-1)
a = js.Substring(0, js.IndexOf("//"));
b = js.Substring(js.IndexOf("\r\n", js.IndexOf("//")));
js = a+b;
//Removing multiline comments
while (js.IndexOf("/*") != -1)
a = js.Substring(0, js.IndexOf("/*"));
b = js.Substring(js.IndexOf("*/", js.IndexOf("/*"))+2);
js = a + b;
//To Remove Blank spaces
js = js.Replace(" ", string.Empty);
//To remove Carrige retun and new line character
js = js.Replace("\r", string.Empty);
js = js.Replace("\n", string.Empty);
//Flushing it in response
//Closing the resourses used

You can get the same from my article in CodeProject