Form Elements in ASP.NET Master Pages and Content Pages
OK, another road bump in my current project.
I have never had form elements in both my master and content pages, I tend to have all the forms in the content where relevant.
In the current project however, we have a page where they want both. A login form at the top right, and a questions form in the content.
Having tried to get this in, I have run in to the issue of ASP.NET moaning about the need for a single form element in a master page. TBH, I really dont get why this is a requirement on ASP.NET's part, but hey ho.
Does anyone know if/how I can get the master and content pages to contain form elements that work independantly?
If not, can you offer advice on how to proceed to get the desired look/functionality?
Answer
Thought I would review some of my outstanding questions and see if I can close some of them off.
This one was an interesting one. I outright refused to believe you can only have one form on an ASP.NET page. This to me made no sense. I have seen plenty of webpages that have more than one form on a web page, why should an ASP.NET page be any different?
So, it got me thinking.
Why does a ASP.NET page need a form element?
ASP.NET pages try to emulate the WinForms environment, by provided state persistance through the PostBack model. This provides an element of state to a stateless environment. In order to do this, the runtime needs to be able to have the ability to maintain this state within each "form". It does this by posting back data to itself. It's important to note that:
- There is nothing really fancy about a PostBack.
- It uses a HTTP form and POST, the same as any other form, from any other stack.
- Just because it looks like it might be doing something special, its not, all that happens is it POST's back with some info about what caused it, so you can do things like handle client-side events, in server-side code.
So why only one?
This to me was the million pound question (I am British). I understand that ASP.NET needs this, especially if you are using ASP.NET server controls, but why the hell can't I make my own additional forms?
So, I thought screw it, just make your own form!
And I did. I added a bog-standard, simple form with a submit action of "#". This then performs a POST to the current page, with the Form data for the given form in the request.
Guess what? It all worked fine. So I ended up with:
- A master page, with a HTML form in
- This form posts back to the current page (basically the page using the master).
- In the Page_Load code-behind for the master, I then added code to check the request to see what data was passed in the request. If it contains data (say a hidden field) then I know the post was sourced from the Form on the master page, if not, then it is most liekly a PostBack from content, and can be ignored.
- I then surrounded the Content tags with
<form runat="server" id="aspNetForm"...> </form>tags. This meant that all content pages automatically had a form to work with.
This provided me with a relatively simple, clean solution to my problem. My login form works fine in tandem with all the content forms created, some of which are complex forms, others use lots of server controls and many PostBacks, and so on.
I hope this helps others.