Change in Web.config no longer requires a restart, hence no loss of Session. Cache ...

 

Earliar in .Net1.x whenever there is any change occurs in Web.config, it results into restart of ASPNet Worker Process [aspnet_wp.exe].  This in turn results in loss of Session State, Cache …..

 

But with a quick fix in .Net2.0, we can get rid of this and freely make any changes.

 

Note: Major of the changes are required in the ‘appSettings’ section. However changes can be done in any of the sections in Web.config.

 

Fix is as below:

·         Introduce External Config files. i.e. Instead of placing the attributes of a section in Web.config, place them in an External config file and place a reference to the external file in that section of Web.config.

 

Example:

 

o        By default below is found in Web.config:

 

<?xml version="1.0"?>

<configuration>

                  <appSettings>

                        <add key="message" value="Changed" />

</appSettings>

<system.web>

<trace enabled="false" requestLimit="100" />

</system.web>

</configuration>

 

o        Introduce the concept of External Configuration as below:

 

<?xml version="1.0"?>

<configuration>

                  <appSettings configSource="appSettings.config" />

                 

<system.web>

<trace configSource="trace.config" />

</system.web>

</configuration>

 

o        Below are the individual config files.

 

appSettings.config

 

<?xml version="1.0"?>

<appSettings>

  <add key="message" value="Hello" />

</appSettings>

 

Trace.config

 

<?xml version="1.0"?>

<trace enabled="false" requestLimit="100" />

 

·         Use ‘restartOnExternalChanges’ attribute. [New in .Net 2.0]

o        This attribute is found in machine.config

o        By default value of this attribute is ‘true’.

o        But for the ‘appSettings’ and ‘system.data.dataset’, the values is set to ‘false’ in machine.config.

 

e.g.

 

<section name="appSettings" type="System.Configuration.AppSettingsSection, System.Configuration, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" restartOnExternalChanges="false" requirePermission="false" />

 

o        For the mentioned example to work, lets us set it for ‘trace’ section also.

 

<section name="trace" type="System.Web.Configuration.TraceSection, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" restartOnExternalChanges="false"/>

 

 

 

Now make changes as below.  These changes will not result into restart and Session loss.

 

Code to change ‘appSettings’ section:

 

Configuration config = WebConfigurationManager.OpenWebConfiguration(Request.ApplicationPath);

AppSettingsSection section = (AppSettingsSection)config.GetSection("appSettings");

KeyValueConfigurationCollection coll = section.Settings;

string str = coll["message"].Value.ToString();

section.Settings["message"].Value = "Changed";

config.Save(ConfigurationSaveMode.Modified);

 

 

Code to change ‘trace’ section.

 

Configuration config = WebConfigurationManager.OpenWebConfiguration(Request.ApplicationPath);

TraceSection section = (TraceSection)config.GetSection("system.web/trace");

section.Enabled = !section.Enabled;

section.RequestLimit = section.RequestLimit - 5;

config.Save(ConfigurationSaveMode.Modified);

 

Note:

·         Use restartOnExternalChanges with some care, as some parameters can truly only take effect if the application restarts.

·         If you do set restartOnExternalChanges to false for a section, make sure not to cache the parameters for the section in our application, and always read values through the WebConfigurationManager.

 

 

Regards,

Arun Manglick…

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