a beginner's guide to asp.net application folders
TRANSCRIPT
A Beginner's Guide to ASP.NET Application Folders
Table of Contents
Overview ASP.NET Application Folders
Advantages of ASP.NET Application Folders
Different Types of Application Folder
Details of Application Folders
App_Code Folder
Bin Folder
App_Data Folder
App_Theme Folder
App_Browser Folder
App_WebReference Folder
Resource Folders
App_LocalResource Folder
App_GlobalResource Folder
Overview - ASP.NET Application Folders
ASP.NET 2.0 uses a file-based approach. That means, all class files, resource files, data files and
folders are maintained in a hierarchical structure. If we are working with ASP.NET 2.0, we can
add files and folders using the Add Itemsoption. If we look at a sample application hierarchy, it
will look like the following figure.
We can add as many as files and folders as we like (according to our requirements) within our
solutions,and it won't be necessary to recompile them each and every time they are added. It is
ASP.NET'stask to dynamically compile them when required. So, what ASP.NET 2.0 does is, it
uses a predefined folder structure containing the files (classes, images, resources, etc.), to
compile them dynamically and we can access those files throughout the application. ASP.NET
also provides special folders to maintain files and resources. Let's see the advantages of using
these folders.
Advantages of ASP.NET Application Folders
Following are the main advantages of use of ASP.NET's Application Folders
We can maintain resources (classes, images, code, databases, themes) in an organized
manner, which allows us to develop and maintain sites easily
All files and folders are accessible through the application
We can add as many files as required
Files are compiled dynamically when required
Different Types of Application FolderASP.NET treats the following folders in a special manner. They are:
App_Code Bin App_Data App_Theme App_Browser App_WebReference App_LocalResource App_GlobalResource
Details of the Application FoldersNow, to look at the use of these folders, I am going to start from App_Code.
App_Code Folder
As its name suggests, the App_Code Folder stores classes, typed data sets, etc. All the items that
are stored inApp_Code are automatically accessible throughout the application. If we store any
class files (like .cs or .vb) it compiles them automatically. It automatically creates type data sets
from .xsd (XML schema) files, and creates XML web service proxy classes from WSDL.Let's
have a look at how we can use the App_Code folder.
We can add an App_Code folder, by Solution File → right click → Add ASP.NET
Folder → App_Code. The App_Codefolder is now added to your application.
Note: Try to add one more App_Code folder by using the same steps.Oops...
the App_Code folder is no longer available there. So, ASP.NET allows you to add
an App_Code folder only once.
Now we can add new items like classes, text and xml files into the App_Code folder and we can
also add existing files there.
Let's have a look at one example that shows how it works. Into the App_Code folder, I have
added a classMyCSharpClass.cs.
In that class I have written a small spice of code for adding two numbers.
Now, Try to access this class, from any where in your application. You will see
that MyCSharpClass is accessiblethroughout the application.
If we want to store different classes like .cs or .vb, then what will happen? If we kept
both .cs and .vb classes in the same folder, it will give following compilation error:
This is because all the classes contained in the App_Code folder are built into a single assembly
and it can't have different languages at root level, or even at child level folders in following
manner:
We have a solution to overcome this problem. We have to create separate folders for C# and for
VB or other classes.
Store class files separately in those folders and an configure the folder hierarchy in
the web.config file.
Now I will move to our next part -the Bin folder.
Bin Folder
The Bin folder is used for keeping assemblies inside it. We can access those as a reference from
anywhere of our web application. Use of Bin folder comes into the picture if we use any class
library within our web application. Suppose we are creating a class library called TestLib. After
building the library, we will get TestLib.dll. Now, right click on solution file → Add
References → Project, select the TestLib Project, click on OK. Check the Bin folder, it will
containTestLib.dll and TestLib.pdb files.
Assemblies in the Bin folder do not need to registered on the system, ASP.NET recognizes the
presence of DLLs inside the Bin Folder. Keeping .pdb files inside Bin folder helps us in
debugging. The main limitation of storing assemblies in the Bin folder is that their scope is
limited to the current application. Therefore, they cannot access any code outside of current web
application. [Source]
Next, let's have a look at App_Data folder.
App_Data Folder
The App_Data folder is used as a data storage for the web application. It can store files such
as .mdf, .mdb, and XML. It manages all of your application's data centrally. It is accessible from
anywhere in your web application.The real advantage of the App_Data folder is that, any file you
place there won't be downloadable.
We can add .mdf files to the App_Data folder directly by selecting Add New Item. From there
we can a create table, procedure or function without opening SQL Server.Now if we want to add
that data to our application, we can easily use it.
Now, look at the connection string that we need to write for accessing the App_Data folder's
databases.
We can connect with MyDB.mdf database using this connection string. Check the example
below, which I have used to read the table data from the MyDB.Mdf file.
App_Theme Folder
If you want to give your web sites a consistent look, then you need to design themes for your
web application. TheApp_Themes folder contains all such themes. An App_Theme folder can
contain two subfolders; one for CSS files and the other for skin files. When we add
an App_Theme folder, a subfolder with name Theme1 will be automatically created. We can
change the name of the theme folder as per our requirements.
I will not cover how to create skin files or CSS file in this article, my main concern here is how
to apply them. You can easily find the details ofskins and CSS via Google.
Now that we have to apply the theme to the page, there are several way to do that. We could set
the theme fromaspx page using a page directive in following way:
While we are going to set themefrom aspx page, the list of themes available to us is as shown in
the figure. We can set the theme from the code behind file also, and we can even change theme
at runtime (using HttpHandler).
App_Browser Folder
The App_Browser folder contains browser information files (.browser files). These files are
XML based files which are used to identify the browser and browser capabilities. You will find
the browser files in the following location:
If you want to change a .browser file, just copy the file to the App_Browser folder and change it.
You can create new browser files by just clicking on Add New Item of the App_Browser folder
As I already mentioned, a browser file is a configuration file, it generally looks like this:
App_WebReference FolderAs the name suggests, the App_WebReference folder contain references to any web services. If
we added any web services with our web application, they go automatically into
the App_WebReference folder, in the same way as in windows applications, if we added any
DLLs, they would go under the Reference folder.
Resources Folders
Before starting on the App_GlobalResource and App_LocalResource folders, I would like to give
a small introduction on ASP.NET resources. If you are, say, creating sites for a multinational
company, or a public web sites that can be accessible from all over the world, you need to
consider the best way to address users in different cultures and different countries in different
languages. ASP.NET provides the infrastructure to create web applications that automatically
adjust formatting and language according to the user's preferences, by using resource files.The
main purpose of resource files is localization of the web application.
ASP.NET uses resource files to make supporting multiple languages simpler. Visual Studio 2005
can automatically generate XML resource files that contain text for your controls in different
languages. When a user visits the sites, they can change the languages of the sites based on their
preference. There are two type of resources:
Local resources
Global resources
The App_LocalResource folder contain local resource files and the App_GlobalResource folder
contains global resource files.
App_LocalResource Folder
Local resources are specific to a single web page, and should be used for providing multilingual
functionalityon a web page.
Local resources must be stored in the App_LocalResource subfolder of the folder containing the
web page. Because you might have local resources for every page in your web application, you
might have App_LocalResource subfolders in every folder.
Resource file names should be like <pageName>[.langauge].resx. Some examples of local
resource files are,Mypage.aspx.ex.resx and Mypage.aspx.de.resx. Default.aspx.resx is the base
resource file to use if no other resource file matches with the user's current culture.
If you want to create local resources for a page, open the design view of the page and then
from Tool Menu selectGenerate Local Resource. You will then see that a resource file is
automatically created in the correspondingApp_LocalResource folder.
Note: Default2.aspx.resx is the resource file for Default2.aspx, and Others.aspx.resx is the
resource file forOthers.aspx. Both resource files are inside the App_LocalResource folder.
The following code shows you the XML code for the resource file. To change the resource file,
we can either change the XMLdirectly or use the Resource Editor.
If we change anything on the page, the resource file will be automatically updated. If you want a
test application for Local_Resource, just create a copy of Default2.aspx.resx and rename it
to default2.aspx.fr.resx (for French resources). Now, as a test, I have changed the button's tool
tipfor the French resource to "French ToolTip". Now change your web browser settings and
set French as the default culture.
(For Internet Explorer, use Tools → Internet options → Languages, add French to the top of
the list and test the application)
Test the button tool tip in this way, and you can test it for other languages also.
App_GlobalResource Folder
The App_GlobalResource folder can be read from any page or code that is anywhere in the web
site. Global resources must be stored in the App_GlobalResource folder at the root of the
application. We should use theApp_GlobalResource folder when we need a single resource for
multiple web pages. We candefine ASP.NET control properties by manually associating them
with resources in global resource files.You can add a global resource file by right clicking on
the App_GlobalResource folder and clicking on Add Items. Add .resx files as resources.
We can access these resources programmatically by using the Resource.Resource object.
E.g.:
Label1.Text = Resource.Resource.MyText
We can use the GetLocalResourceObject() and GetGlobalResourceObject() methods to access
global resources, and then cast them to the correct type.
Label1.Text = GetLocalResourceObject("Label1.Text").ToString();