I would like to be able to create projects that contain multiple files so that I can create tutorials to teach student.
The MVC project type for example allows for multiple files. but they are all together on screen and I can't close one down to focus on say the controller.

VS Code uses Theia https://www.theia-ide.org/index.html - Perhaps you could also use this in your UI?

This would really help to make samples of bugs / issues in a repository. One could import all the files of a repository, then write a "Test" that fails and the owner of the repository could then check out why it fails easily.

See for example me manually uploading the files in a competitors product:
https://repl.it/@devedse/ErrorWhenLoadingJpgWithExif

Simple test:

static (int, int) Foo(int i)
{
return (i+2, 1*2);
}

Current "result" :
Predefined type 'System.ValueTuple`2' is not defined or imported

Expected:
To compile (and work of course :-)

This includes updating "4.7.2" "Compiler" to accept C# 7.x and at least linking the proper dll with ValueTuple-a for "Roslyn 2.0"

Why would you make a Nuget Header Directive available for C# but not for VB.Net?

It would be nice to have a user page that lists the Fiddles that we have created. A main page of sorts.

Sometimes I need to check a code that works with local timezone which should be different from UTC. It would be great to have an ability to specify timezone in that cases. Thank you!

Such as controller or class or new .cHTML ...

Change the text color with Console.ForegroundColor

That the code can be used:
Console.ForegroundColor = ConsoleColor.DarkBlue;

Console.Write ("Hello");

Console.ForegroundColor = ConsoleColor.DarkRed;

Console.WriteLine ("World");

Please add this, at least as an option. Otherwise we can lose work. Thank you!

some class libraries loaded from nuget need setting assembly attributes located in assemplyInfo.cs otherwise it fire an exception, like:

[assembly: AssemblyCompany("Company xyz")]
[assembly: AssemblyCopyright("Copyright © 2018 Company xyz")]

Enable setting these attributes in assemplyInfo.cs

Allow the usage of debugging such as stepping into a function, out of a function, run, memory mapping, local variables and the whole nine yards. It is vital if you don't want users to write constantly Console.WriteLine() statements.

Kindly, add debugging!

Please enable vim key bindings. VsVim is one of the most downloaded Visual Studio extension, which is an indication of Vim key binding's popularity among .net devs.

For example: I define a class Person in a fiddle named PersonClass.
Then I base a new fiddle PersonUseExample on existing fiddle PersonClass, so I don't need to declare the class again, just démonstrate how I can use it.

The idea is probably easier to implementis but similar to the exiting request: https://dotnetfiddle.uservoice.com/forums/228764--net-fiddle-ideas/suggestions/6056568-allow-multiple-files-for-console-projects

When try to add nuget package System.Text.Encoding, keep receive error in browser console: common:Uncaught Error:

Uncaught Error: Incorrect version name
at Object.n.addPackage (common:1)
at HTMLAnchorElement.<anonymous> (common:1)
at HTMLBodyElement.dispatch (jquery:1)
at HTMLBodyElement.y.handle (jquery:1)

On top of each fiddle, it says "by <author's user name>". The author's username should be a link to take the user to all his/her fiddles.