ReadOnlyNameValueCollection (reading from ConfigurationManager.GetSection)

Ok, so.....

<section name="test" type="System.Configuration.NameValueFileSectionHandler" />
<test>
   <add key="foo" value="bar" />
</test>

var test = ConfigurationManager.GetSection("test");

So far so good. The debugger shows test contains one key, foo.

But GetSection returns object, so we need a cast:

var type = test.GetType();
// FullName: System.Configuration.ReadOnlyNameValueCollection
// Assembly: System

Ok, this should be simple enough. So....

using System;

var test = ConfigurationManager
               .GetSection("test") as ReadOnlyNameValueCollection;

error!

The typ开发者_StackOverflow中文版e or namespace ReadOnlyNameValueCollection does not exist in the namespace System.Configuration. Are you missing an assembly reference?

err... wtf?

A cast to System.Collections.Specialized.NameValueCollection gets the code working, but I don't really understand why the error.

And a search for ReadOnlyNameValueCollection on MSDN shows there is no documentation on this class at all. It doesn't seem to exist. Yet I have an instance of that type in my code.

System.Configuration.ReadOnlyNameValueCollection is an internal class to the System.dll assembly. So you can't refer to it from your code. It derives from System.Collections.Specialized.NameValueCollection, though, so that's why you're able to do that with the cast.