What is the proper way to include code from an external file in ASP.NET?

Question

I've been using PHP for years to build websites. Often I will use an include to bring in, say a navigation menu:

<?php include 'includes/nav.php'; ?>

I am much more of a novice when it comes to ASP.NET (C#). I am wondering what is the correct (and most efficient) way of doing the equivalent of a PHP include, in ASP.NET?

Answer 1

Disclaimer: I have no experience with PHP and I am making some assumptions based on what I know.

In a regular C# file (including ASP.NET Web Forms code behind file or ASP.NET MVC controller) there is the using statement that imports a namespace. It looks like this:

using ParentNamespace.ChildNamespace;

This allows you to use classes in the ChildNamespace without typing the full name of the class ParentNamespace.ChildNamespace.SomeClass. Keep in mind that before doing this you must add a reference to the assembly (usually DLL file) in the references of your project (managed via the References kind-of folder in Visual Studio). A single assembly can have multiple namespaces and classes and there are some assemblies added by default in standard project templates.

In an ASP.NET Web Forms project you can reference what is called user controls. User controls are encapsulated view + code behind much like your page that are really easy to reuse. You reference the control on the top of your page (or control) like this:

<%@ Register src="~/Folder/Subfolder/MyControl.ascx" tagname="MyCustomControlName" tagprefix="myCustomPrefix" %>

and then at the place where you want your control you use it like this:

<myCustomPrefix:MyCustomControlName ID="myControl" runat="server" />

In ASP.NET MVC you can reference namespaces with using in code blocks (the syntax depends on the view engine you are using but it is something with using) and you can reuse other views by calling the Html.RenderPartial method like this:

Html.RenderPartial("MyCustomView");

Another way to get kind of reverse reference around a page are Master Pages. They allow you to define place holders for the content of your page.

Answer 2

If you want to reference and use a control.

<%@ Register Src="includes/Nav.ascx" TagPrefix="uc" TagName="Nav" %>

You can later add the control on your page.

<uc:Nav ID="navMenu" runat="server" />

If you want to reference a namespace to use in a code block <% code here %>

<%@ Import Namespace="Includes.Nav" %>

Answer 3

One way accomplish this is by using Master Pages

You define layouts and "pin-points" on these layouts.

Another way is using User Controls. You put markup in a separate file (*.ascx) and then reference it in pages or master pages (this is more like include).

I advise you, in the most polite way, to read a book about ASP .Net.

Answer 4

Probably the most analogous ASP.NET construct to PHP's include, based on your example, is creating and referencing a user control. This allows you to predefine markup as well as any server-side functionality in an ASCX file, which you can use into your page.

You can also use a master page, as someone stated below, which flushes out your basic layout and lets you define content place holders, which other pages can implement and fill in the content. Master pages are a popular approach for defining page elements that are consistent across all pages, like your nav there (also things like headers, footers, common scripts, CSS, etc.).

Answer 5

You don't really include code as text this way. ASP.NET operates on classes and assemblies. Depending on how you are building your asp and what you are attempting to do. You can add a reference to a dll or drop the class in the special classes folder. If you are attempting to share layout the use a master page is common.

Answer 6

It depends on the role that the include file plays. Reusable bits of content can be created as User Controls, or it might form part of a Master Page.

Have a look at this article: http://www.mikesdotnetting.com/Article/144/Classic-ASP-Include-Files-in-ASP.NET