Can the C# interactive window interact with my code?

When using Visual Studio 2015:

You can open the Interactive window by navigating to Views > Other Windows > C# Interactive,

Then just right click your project and run Initialize Interactive with Project from the context menu.

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For older versions:

To use the C# Interactive Window with your code, ensure you first compile your code, then add a reference to the resulting assembly with the #r command like so:

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You can also use the Immediate Window to interact with your code as well, like so:

You can use classes from your own project.
Just right click on your solution and select "Reset Interactive from Project".

If you need more information, here is the source:
Using the C# Interactive Window that comes with Roslyn – Part 2

Just an update from the @Botz3000 answer.

The command you want to find is now called "Initialize Interactive with Project"

Also it is worth noting i could not find this command if my C# interactive window was not viewable.