Simple ConfigManager
This caught my eye:


    if (!IsInitialized)
        throw new NotImplementedException("Config data has not get been implemented.");



A NotImplementedException is usually a kind of "meta" exception that you typically find in unimplemented method stubs, e.g.

public string GetConfigElement(string key)
{
    throw new NotImplementedException();
}


It's basically ilke a "todo" marker that [intentionally] blows up at runtime:


  You might choose to throw a NotImplementedException exception in properties or methods in your own types when the that member is still in development and will only later be implemented in production code. In other words, a NotImplementedException exception should be synonymous with "still in development."
  
  MSDN


Throwing that exception as part of the implementation of a method is confusing; in this case the goal is to tell the caller that the current state of the object does not allow using this method yet.

In other words it should be an InvalidOperationException:


  The exception that is thrown when a method call is invalid for the object's current state.


See the remarks section on MSDN for more guidelines on throwing that specific exception.



I find the constructor is doing too many things:

var foo = new ConfigManager(path);


With this single instruction, I've just hit the file system, read the contents of some file, and cached a number of configuration settings in an encapsulated dictionary.

The problem is, if I wanted to write a unit test to document how the GetConfigElement works (and then another to document how it fails), I couldn't, because my test would depend on file I/O.

I'd suggest moving that logic out of the constructor, and delay doing that work.



It would be nice to include an indexer, so client code could do this:

var foo = new ConfigManager(path);
var port = foo["port"];


That said you're reinventing the wheel here, if this is production code you should probably be using the framework-provided XML configuration, using the System.Configuration namespace; you could store your connection strings in a dedicated &lt;ConnectionStrings&gt; section.