From the past to the PostBack in Visual C#.NET

Printer Code 39 in Visual C#.NET From the past to the PostBack

Having to handle the header had a lot of problems when it came to the sophisticated Web forms that ASPNET provides, so Microsoft used JavaScript to short-circuit the process They created a special method that would be on every page that ASPNET generates

This method formats the information in order to better manage the communication with the server A PostBack looks like this:

POST /admin/Pages/Add_entryaspx id=e387aab8-1292-4c75-985f-5f8e5db3089a HTTP/11 Accept: application/x-ms-application, image/jpeg, application/xaml+xml, image/ gif, image/pjpeg, application/x-ms-xbap, application/vndms-excel, application/vndms-powerpoint, application/msword, application/x-shockwaveflash, */* Referer: http://wwwsempfnet/admin/Pages/Add_entryaspx id=e387ccb8-1292-4c75985f-5f8e5db3089a Accept-Language: en-US User-Agent: Mozilla/40 (compatible; MSIE 70; Windows NT 61; WOW64; Trident/40; SLCC2; NET CLR 2050727; NET CLR 3530729; NET CLR 3030729; Media Center PC 60; NET CLR 114322; InfoPath2; OfficeLiveConnector13; OfficeLivePatch00) Content-Type: multipart/form-data; boundary=--------------------------7d922c323b0016 Accept-Encoding: gzip, deflate Host: wwwsempfnet Content-Length: 9399 Connection: Keep-Alive Pragma: no-cache -----------------------------7d922c323b0016 Content-Disposition: form-data; name= __LASTFOCUS

-----------------------------7d922c323b0016 Content-Disposition: form-data; name= ctl00$cphAdmin$txtTitle C# 40 at CONDG -----------------------------7d922c323b0016 Content-Disposition: form-data; name= ctl00$cphAdmin$ddlAuthor Admin -----------------------------7d922c323b0016 Content-Disposition: form-data; name= ctl00$cphAdmin$txtDate 2009-09-08 22:21 -----------------------------7d922c323b0016 Content-Disposition: form-data; name= ctl00$cphAdmin$txtContent$TinyMCE1$txtCont ent <p>I was very pleased to be able to give my C# 40 talk at the <a href= http:// wwwcondgorg/ >Central Ohio NET Developers Group</a> last month</p> -----------------------------7d922c323b0016 Content-Disposition: form-data; name= ctl00$cphAdmin$txtUploadImage ; filename= Content-Type: application/octet-stream

-----------------------------7d922c323b0016 Content-Disposition: form-data; name= ctl00$cphAdmin$txtUploadFile ; filename= Content-Type: application/octet-stream

-----------------------------7d922c323b0016 Content-Disposition: form-data; name= ctl00$cphAdmin$txtSlug C-40-at-CONDG -----------------------------7d922c323b0016

Notice the nice layout of the data, with the form field name, and the data and everything all nice to read Fortunately, you don t have to worry about any of this ASPNET gets it for you When you create an event handler for an object a button, for instance a PostBack will be used for that communication This is how ASPNET changes your interface with the server and client It makes Web programming look like Windows programming, at least as far as events are concerned

The other major piece of the puzzle in Web server usage is state No, I don t mean that field in the Address database I mean that the server should know the state of the application at any given time Web servers don t do a very good job of remembering state because of one of the problems with Web browsers inconsistency of communications Because the server doesn t know if you are going to send anything from one minute to the next, they can t depend on getting it For this reason, the server tries to remember certain things about your session by putting values in the form that they can use later The server uses a ViewState value for that The ViewState is an encrypted string that the server can use to remember who you are from POST to POST Even with these values, maintaining session state has its problems For instance, in a secure application you might need to maintain a transaction for a database function This is nearly impossible in a Web application, because you can t be sure you will get the return acknowledgment Because of this, nearly all the data processing happens on the server I cover this in more detail in 5

Looking at How ASPNET Works with C#

here is a lot to Web development People used to ask me what language I programmed in I told them I was a Web developer

No, really, what language do you program in they would ask Web It s seven languages Seven that I have to know Criminy, is it really seven At the time, it was seven I needed to know SQL, VBScript, XML, Visual Basic, HTML, CSS, and JavaScript At least it is a little better now You can get by without C++, which was once required Oh, and C# can replace Visual Basic The rest With Visual Studio in the mix, things are a little easier than they once were You have two considerations when you choose Visual Studio to be your tool of choice to build a Web application The first is the tool itself The second is the way you are going to use the tool, or your methodology If you ve been working with the samples in this book, working in Visual Studio is going to feel very familiar There is a design view for the user interface Code View works just like the Code View in all the other environments The only caveat is the unusual file types that you will see occasionally in Web applications You ll get used to those I did The methodology debate that is, which methodology works better is harder to get used to because it is a religious war People will tell you to use one or the other for this reason and that I do the same thing here Feel free to ignore me Just don t use something only because it is new and shiny Do the research, try things, and build software that works In this chapter, you see how to build an application in one methodology, using Visual Studio as your tool