Develop Reference

How to create single page and render many pages in ASP.net

i want to create an ASP.NET website, what i want to do is to create a page lets name it the main page "main.aspx", not MVC or razor pages.
Then inside this page i control and render the other pages using paramter in the url named "method" for example as following :
main.aspx?method=register : so the register page or view rendered in the main page.
main.aspx?method=users : the users page or view rendered in the main page.
My question is, what it the right choice to do this in Visual studio 2017 ?
if web forms is the right one, what is the main page should be "Default.aspx" or another page ? where i should exactly get the "method" value ? where i should put the template or the view of the "register" for example? and what is the expected content to be inside it ?

It sounds like you want a Single Page Application type of site.
My question is, what it the right choice to do this in Visual studio 2017 ?
Sure it is, if you understand what you are building. Try creating a new ASP.NET Core project with the SPA template, and see if that is what you are looking for. If so, I would strongly suggest checking out the [ASP.NET SPA Documentation(https://learn.microsoft.com/en-us/aspnet/web-api/overview/getting-started-with-aspnet-web-api/build-a-single-page-application-spa-with-aspnet-web-api-and-angularjs)..

If you use Webforms, the template that can wrap other pages is called a MasterPage.
You don't need to pass the page name through a querystring, though. You can accomplish that with the URL Rewrite module or with Routing, but neither is necessary. The MasterPage will wrap any page that uses it automatically.
Here's an overview:
ASP.NET Master Pages
https://msdn.microsoft.com/en-us/library/wtxbf3hh.aspx

Implementing an html/css framework with a master page in visual studio

I'm working on a website for a school project and I designed it in photoshop with 9 columns.
To make life easier I want to use the 960 grid system (Custom for 9 columns) in order to build the design in html/css.
Part of the projects requirement is that I need to use a master page and web forms in c# however I'm not sure how to implement the 960 framework within that.
does anyone have any experience with this?

It sounds like you're being forced to use ASP.Net Web forms. I'd typically recommend you use ASP.Net MVC instead, and it does support Master pages, but really everything is a view, and I expect you would get push-back from the professor. So, to keep with the standard ASP.Net Web forms approach, you should create a new ASP.Net WebSite, and check off that you want a master page. Then Visual Studio will create the Master page for you, and any new aspx pages you create you can click a box to have them inherit from the master page.
If you look at the .Master page, you'll see the same HTML you would see on any site, including the , and tags. You should just include the .css file that contains your 960 framework file, just like you would on any Web page. Then the rest f the page will use the 960 grid, and you can put the necessary col# classes inside the class tag (or CssClass for ASP.Net controls) to get the display to work correctly.

Share webpages between multiple websites (Best Way)

I have created two websites using C# in Visual studio 2008. Both websites having common maintenance (User and Role) pages. I have also create a common class library (C#) and added reference to both website, which is working properly.
I don't want to replicate/maintain the multiple copies of the same aspx pages.
Is there any better way except user controls, to have single copy of common aspx pages and add reference to both website, just like class library?
Thanks.

In your response to Mr.Lister it sounds like you aren't using a master page, and your really should.

What is equivalent to a php page setup in asp.net

I program php, but I am trying to get into c# asp.net. In php I can make forms, custom html, etc into a seperate php file and just include it on the page that I desire. I understand asp.net has a master page which allows you to set the template for the whole website, but what If I want just a row of buttons to be on SOME pages, and not all? something separate to the master page that can be included on any page i desire? Also when its controllers is that when I use .ascx?

Look at User Controls. You can program a control that consists of a row of buttons and then put it on whichever pages you like.

There are two different approaches to ASP.NET nowadays.
ASP.NET WebForms:
Each page (.aspx) can have a Master Page (.master). Each master page can further have its own master page. Master pages are optional altogether, but if present, at least one in the heirarchy will typically have the opening and closing html, head, body, and form tags.
Each page (and master pages too) can reuse html/logic within itself through Web User Controls (.ascx), for instance if you wanted to create a reusable comment box "control".
ASP.NET MVC:
Each View can have a master layout.
Each View or master layout can trigger the rendering of child/partial Views, for further reuse of html/logic.
Nowadays, if coming from PHP, I'd learn ASP.NET MVC instead of WebForms if I were you.

As DuckMasetro. Said, we can have master Page Concept. It Is easiest way to do.. You can Design master pages in Designer mode with liitle efforts. then Just Use MasterPageFile="url" this property in your Webforms Page Directive at the top of your aspx. page
Tutorials for Begginers
Documentation for Master Page in ASP.net

Create master page at runtime

Hi
I want to create a master page dynamically by the user like the one DotNetNuke is done
and load the modules where the user needs. I also want to have nested master pages with the above approach.
Please help me design the above problem.

Checkout:
Really Dynamic Master Pages
Nested Master Pages
Nested ASP.NET Master Pages

DotNetNuke has a very permissive open source license. You can use the Skin code from DNN in your own projects. Get the source here.