Can the C# interactive window interact with my code?

In Visual Studio 2015 or later, I can open the 'C# interactive window', and run code:

> 5 + 3
8

That's cute. Now how can I interact my code—my classes? Assume I have a project open.

> new Cog()
(1,5): error CS0246: The type or namespace name 'Cog' could not be found (are you missing a using directive or an assembly reference?)

When using Visual Studio between 2015 and 2022:

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.

It's worth noting that the feature isn't yet supported in VS 2019 for .Net Core project.

You won't find the option, and it's a known issue as highlighted in this answer https://stackoverflow.com/questions/56042332/initialize-interactive-with-project-is-missing-for-net-core-projects-in-visua

The workaround is to use #r command (#r "Path/MyDll.dll") to load the assembly manually as seen in the answer above.

Totally agree "Initialize Interactive with Project" is cool.

My approach is to push classes into a library and use //css_reference in C# script or #r in C# Interactive window

For example:

#r "D:\\dev\\DbHMonData\\LoadH2Stats\\bin\\Debug\\DbHMonStats.dll"
using DbHMonStats;