Azure : can we check if a setting exists before trying to read it?

Question

I currently use RoleEnvironment.GetConfigurationSettingValue(propertyName) to get the value of a setting defined in my WebRole config file (csdef + cscfg). Ok, sounds right.

This works well if the setting exists but failed with an Exception if the setting is not defined in the csdef and the cscfg.

I'm migrating an existing app to Azure which has many configuration settings in web.config. In my code, to read a setting value, I d'like to test : if it exists in the webRole config (csdef + cscfg) I read it from here, otherwise I read it with ConfigurationManager from web.config. This would prevent to migrate all settings from my web.config and allow to custom one when the app is already deployed.

Is there a way to do this ?

I don't want to encapsulate the GetConfigurationSettingValue in a try/catch (and read from web.config if I enter the catch) because it's really an ugly way (and mostly it's not performance effective !).

Thanks !

Answer 1

Update for 1.7 Azure SDK. The CloudConfigurationManager class has been introduced. The allows for a single GetSetting call to look in your cscfg first and then fall back to web.config if the key is not found.

http://msdn.microsoft.com/en-us/LIBRARY/jj157248

Pre 1.7 SDK Simple answer is no. (That I know of)

The more interesting topic is to consider configuration as a dependency. I have found it to be beneficial to treat configuration settings as a dependency so that the backing implementation can be changed over time. That implementation may be a fake for testing or something more complex like switching from .config/.cscfg to a database implementation for multi-tennent solutions.

Given this configuration wrapper you can write that TryGetSetting as internal method for whatever your source of configuration options are. When this feature is added to the RoleEnvironment members, you would only have to change that internal implementation.