Re: System.Configuration.AppSettingsSection doc error?
- From: jialge@xxxxxxxxxxxxxxxxxxxx (Jialiang Ge [MSFT])
- Date: Thu, 27 Sep 2007 05:00:34 GMT
Hello Mark,
Thank you so much for your great feedbacks on the MSDN articles about
AppSettingsSection.Settings property. Our database has logged the error in
the first article
http://msdn2.microsoft.com/en-us/library/system.configuration.appsettingssec
tion.settings(VS.80).aspx. Instead of using NameValueCollection, it should
have been talking about KeyValueConfigurationCollection. A newer version is
in
http://msdn2.microsoft.com/en-us/library/system.configuration.appsettingssec
tion.settings.aspx. However, as you said, it still seems using an improper
example. I have filed an request to the MSDN team to confirm the issue.
Before I receive their response, please kindly refer to the following
example about AppSettingsSection.Settings property. Sorry for the
inconveniences.
For web application:
Configuration configuration =
WebConfigurationManager.OpenWebConfiguration("~");
AppSettingsSection appSettingsSection =
(AppSettingsSection)configuration.GetSection("appSettings");
// or we can call configuration.AppSettings.Setting
if (appSettingsSection != null) {
foreach (string key in appSettingsSection.Settings.AllKeys) {
Response.Write(key);
}
}
For exe application:
string exePath = System.IO.Path.Combine(Environment.CurrentDirectory,
"ConsoleApplication1.exe");
Configuration config = ConfigurationManager.OpenExeConfiguration(exePath);
AppSettingsSection appSettingsSection =
(AppSettingsSection)config.GetSection("appSettings");
// or we can call configuration.AppSettings.Setting
foreach (string key in appSettingsSection.Settings.AllKeys)
{
Console.Write(key);
}
For your question about the difference between NameValueCollection and
KeyValueConfigurationCollection: both implement the interface Icollection
and Ienumerable, but NameValueCollection also implements ISerializable and
IdeserializationCallback. Besides, KeyValueConfigurationCollection does not
support a "Set" method. We could use NameValueCollection.Set to reset a
key's value.
In the configuration file, if a key has multiple values, the default
behavior of ConfigurationManager.AppSettings and
Configuration.AppSettings.Settings is to overwrite the previous value with
the new. That is to say, if in <appSettings> tag, there are items: <add
key="TestKey" value="1"/> <add key="TestKey" value="2"/>,
Configuration.AppSettings.Settings or ConfigurationManager.AppSettings only
returns "2" as "TestKey" by design. Internally, it is using
collection[key] = value; instead of collection.Add(key, value);, therefore,
the old value will be overwritten by the new one, even if
NameValueCollection has methods like GetValues. The development team has
confirmed that it is by design because in majority of the cases, a user
wants to overwrite the value (such as in lower level web.config file for
asp.net applications) instead of adding one more value under the same key.
I am sorry if this design decision does not fit your situation. In order to
support multiple values for a same key, we need to customize the
ConfigurationSectionHandler. Please refer to the following article for more
detailed information.
http://www.codeproject.com/dotnet/namevaluemultiple.asp
Sincerely,
Jialiang Ge (jialge@xxxxxxxxxxxxxxxxxxxx, remove 'online.')
Microsoft Online Community Support
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