1) Introduction
Web site
settings are supplied by the web.config file. The settings are like
connection strings, how many users allowed etc. Sometimes the situation arises
that the configuration settings to be added or revoked without re-starting the
server. In this article, we will see a demo of how do we add new settings when
the site is running. Imagine that the page we are going to develop is used by
the web admin of the site. The goal is adding a new web setting
dynamically, and in the meantime the server will function as usual without any
re-start.
2) About the sample
The page design
screen shot is provided below.
In the user name
section of the page, we add the session variable for the user name when the Set
User Name button is clicked. The Get User Name button
will retrieve the session variable content and displays that the label next to
it.
In the
Application Settings section of the page, we add a web setting dynamically by
clicking the Store button. We should provide a setting name and
an associated value to it in the corresponding text boxes. By clicking the Retrieve
button, we can get the setting value by supplying the setting name.
In this demo, we
are going to add new setting by clicking the Store button and make sure that
session we set before this operation is kept unchanged. OK, Let us start.
3. Session Variable
A session
identifies a user connecting to the website and the session continues until
he/she disconnects from it. Now the session variable is one, which has the
scope of the connected user session and the variable goes out-of-scope when
he/she disconnects the web session. Therefore, once we define and assign a
value to a session variable, the content is available for all the pages within
that session.
In our sample,
we store and retrieve the user name as the session variable.
1) In the button
click handler for the Set User Name, we are setting the content
of the user name in a session variable called “User Name”. Here,
user name is the Key and the value is whatever we specify in the text box next
to Set User Name.
//Sample
01: Store a session variable
protected void
btnSetUser_Click(object sender, EventArgs e)
{
Session["User Name"] =
txtUserName.Text;
}
2) When Get
User Name button is clicked, we get the “User Name” session variable
and display that in the value textbox. Before doing so, we are checking the
session variable User Name is actually having any value. If we don’t have a
value, then we display session is lost. Actually, the message becomes
meaningless when the session is not yet created. This session variable is just
for demo purpose and our goal is modifying the web application setting without
loosing the session variables. So, do not worry about the validation message
and how meaningful it is in a variety of situations.
//Sample
02: Retrieve session variable Name
protected void
btnGetUserName_Click(object sender, EventArgs e)
{
if (null !=
Session["User Name"])
lblSession.Text = Session["User
Name"].ToString();
else
lblSession.Text = "The
Session variable is lost";
}
3) In the clear
button click event handler, we cleared some of the form fields for convenience
while entring the new values
//Sample
03: Clear the form
protected void
btnClear_Click(object sender, EventArgs e)
{
lblSession.Text = "";
txtName.Text = "";
txtValue.Text = "";
}
OK, Let us test
what we have written in the two button click events. The video below shows
setting and retrieving the username in a session variable called User “User
Name”.
Video Steps
1) The
solution is run in debug mode
2)
Then, the user name for the session is set by clicking the Set User Name
3) Finally, the
user name in the session is retrieved by clicking the Get User Name
4. Retrieving the App Settings
1) We use the WebConfigurationManager to retrieve the application settings that is previously saved in
web.config file. When we click the Retrieve button after supplying the setting
name, the settings value is retrieved and displayed in the value text box. The
code for that is given below.
//Sample
06: Retrieve the Setting
protected void
btnRetrieve_Click(object sender, EventArgs e)
{
string
value = "";
if (WebConfigurationManager.AppSettings[txtName.Text]
!= null )
value = WebConfigurationManager.AppSettings[txtName.Text];
txtValue.Text = value;
}
2) Have a look
at the section of code taken from the web.config file, which is given below:
<appSettings>
<add key="pageTitle" value="MsTechArticles.com" />
</appSettings>
In this, we have
only one application setting. The setting name is pageTitle and
the value is MsTechArticles.com.
Now watch the video below which shows retrieving the setting value for
the given key pageTitle.
Video Steps
1) In web.config
current application setting section is previewed
2) Moved to
DynamicSettings.aspx and Run toolbar button is clicked
3) In the form
Setting name (pageTitle) is given and setting value is retrieved
5. Dynamically storing the Settings
The settings are stored in the web
configuration file under different sections. In this article, we are looking at
the AppSettings section only. You can apply what you learn in
this article to any configuration sections (With little exploration when
required). Say for example ConnectionStrings. We use
OpenWebConfiguration method of the WebConfigurationManager to
dynamically add new setting to the web configuration.
//Sample
05: Add New settings
protected void
btnStore_Click(object sender, EventArgs e)
{
Configuration
config = WebConfigurationManager.OpenWebConfiguration("~");
config.AppSettings.Settings.Add(txtName.Text , txtValue.Text);
config.Save();
}
In the above code, we get the reference
to the Configuration object by calling the OpenWebConfiguration available in the root
directory of the web application. If it is not there then we get the settings
from the default configuration of the machine. This configuration is the merged
view of the all the available settings. Therefore, from the config instance, we
get the Application settings to add the application-setting name and the
associated value to it. In our sample application setting and the name is
supplied by the user (Say web Admin). Once the settings added to the required
data structure, we call the save method on the config object.
It is time to check the code written for
storing the application setting. The below given video shows storing the
configuration setting dynamically. It also shows that we add a new entry in the
web.config file, we lose our session and application (Not shown in the demo)
variables.
Video Steps
1) The form is run in the debugger mode
2) A first setting setting1 and
corresponding value is added
3) Then a second setting setting2 and
corresponding value is entered
4) Before clicking the store button, a
session value is stored in a session variable
5) Then, store button of the Application
setting clicked to append one more setting (Setting2)
6) The Get User Name button is clicked,
and Session Variable content loss is shown
7) At last, dynamically added web setting
are shown in the web.config file
6. Dynamic Update of Web Settings without losing the Sessions
We did modification in the web.config
dynamically and all the session variable contents are lost. This we saw in the
previous video. To avoid this we should move the application settings to a new
configuration file. This file is referred as External Configuration
file. Add a new configuration file called settings.config by
right clicking the project name and selecting Add New Item from
the displayed content menu. The picture given below shows entering the data in
the Add New Item Dialog.
The external configuration file is added
to the project after clicking the add button in the “add new item”
dialog. Now go to the Web.Config file and remove or comment out the AppSettings
section. The code given below shows the commented out piece of code in the
web.config file.
<!-- Sample
07: Comment out AppSettings section
<appSettings>
<add key="pageTitle"
value="MsTechArticles.com" />
</appSettings>
-->
Once the above code is commented out, we
should specify the external file name in the web.config file to look for the
AppSettings in it. Web.config file entry for that is shown below:
<!-- Sample
08: Specify the external settings source
-->
<appSettings configSource="settings.config"/>
Now add the AppSettings that is commented
or Removed (From the original web.config file) to the newly created
Settings.config file. The added AppSettings section is shown below:
<!-- Sample
09: Add the App settings in the external source file -->
<appSettings>
<add key="pageTitle" value="MsTechArticles.com" />
</appSettings>
That is all the code change required on
the configuration to make the dynamic update of the web configuration file. Now
we will not lose our session variables when a new entry is added to the web
configuration. This time new settings enter the Settings.config in place of the
web.config. Watch this in the video given below:
Video Steps
1) The form is opened in the browser
2) The settings are entered in the
Application Settings portion of the form
3) Also the session variable is stored
and retrieved in between the settings change
The settings stored in
Settings.config file by the above testing (One shown in the video) is shown in
the below picture:
There is one more point that should be
noted here. The AppSettings by default does not require any server re-start
when we append the settings dynamically. For other sections, you should always
make sure that ReStartOnExternalChanges is set to False. This we should check
on the machine.config file and the screenshot given below shows the default
entry for the appsettings.
Examine the path: <DriveLetter>:\Windows\Microsoft.NET\Framework\v2.0.50727\CONFIG
for machine.config file. Say for example you want to add a new connection
string in the web configuration, the first thing you should do is check the
machine.config file and set the restartonExternalChanges=false. Then follow
what you learned in this article.
Source Code: Download
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