New in .NET 2.0: ConfigurationManager.AppSettings Property

Microsoft now disapproves of the use of ConfigurationSettings (in the System.Configuration namespace) for the retrieval of application and machine configuration settings. The .Net 2.0 now exposes a ConfigurationManager class that "replaces" ConfigurationSettings.

I guess this one should soon be a FAQ (or already is) but I just wanted to write it down. Suppose, you convert a simple 2003 web project to 2005. You compile it. Now you get a warning on ConfigurationSettings.AppSettings Property:

"This method is obsolete, it has been replaced by System.Configuration!System.Configuration.ConfigurationManager.AppSettings"

I want to describe what happens since the warning message is not descriptive enough, imho, especially for people who are not familiar with .NET 2.0 yet.

What to do in order to use ConfigurationManager class ? System.Configuration.dll - ensure you add a reference to this assembly. In .NET 2.0 all configuration functionality is in this separate assembly now. Please note: you can find System.Configuration namespace also in System.dll assembly, for example ConfigurationSettings is still there, so it can cause some confusion.

Unrelated: strange that in VS 2005 solution tree - System.configuration reference visually has "c" in lower case. Why ?

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Anatoly - I'm not following you on this. Do you just need to add System.configuratino with the little c and it will work?

Bill: The code with old ConfigurationSettings class under System.Configuration (under System.dll !) will still compile, but will give a warning that it is obsolete.

i.e. need to use new class ConfigurationManager (now this one is under System.Configuration, but the assembly is different -- System.Configuration.dll -- you have to provide a reference to it to make it work)

My point here is that the warning is not informative and it is not obvious you have to add a reference since you already have System.Configuration under System.dll.

Now, when you add a reference there is a minor bug in VS that visually you see as if it is added as System.configuration.dll in the project tree.

The solution is to add the referance manually. In the Add Reference dialog, scroll down in .NET tab and find System.Configuration. When you add this reference System.Configuration.ConfigurationManager will be available.

Krishan: Why don't you read the post: "System.Configuration.dll - ensure you add a reference to this assembly."

I've added a reference to the System.Configuration and I still find it does not know about the ConfigurationManager (indeed it is not listed in intellisence either)

Paul: Besides the reference you have to add using directive at the beginning of the file.