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!

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

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

Monaco-editor is MIT licensed and made by Microsft.
It's the same text editor used in VSCode, and it is open source!
It also has many interesting features like code diff and editor customization.

See more here:
https://github.com/Microsoft/monaco-editor
https://microsoft.github.io/monaco-editor/playground.html

Roslyn 2.0 is currently in pre-release state. As we get close to RTM, dotnetFiddle will be quite useful to try or demo C# 7 features.

We need the same quick keyboard shortcuts as visual studio...
CTRL+D - Duplicate line
CTRL+K+C - Comment out line
CTRL+K+U - Uncomment line
ALT+ENTER - Automatically add or suggest missing namespace reference and add usings to the class (like resharper)

Given that MS have stopped supporting 4.5.1 and dotnet core has been released, it would be a good time to update the examples.

I would love to use .NET Fiddle in the documentation pages for my OSS projects, but I can't install the packages (I think because of the Framework verisons)

Full roslyn release support

Whenever I add Json.NET as a nuget project, version 6.0.0.0 is attached rather than the selected version. For instance, in this fiddle: https://dotnetfiddle.net/6LyfRc the latest release version is selected, version 7.0.1, but "Console.WriteLine("Json.NET version: " + typeof(JToken).Assembly.FullName);" actually shows 6.0.0.0 was loaded.

In many cases I'd love to be able to have multiple files in a single fiddle so I don't have to throw all my classes in a single file and thus making it harder to read/understand.

Being able to have many files would greatly benefit explaining complex problems/scenarios.

Sometimes it'd be helpful to easily download the source code of a dotnetfiddle paste, either a single file or the whole paste (e.g. all files from a MVC "project")

Allow setting breakpoints for debugging.

In order to practice streaming files and reading from files to demonstrate well written code, you need the ability to upload at least a .txt file to work with. How about you allow .txt files to be uploaded for this purpose?

v4.5, v4, v3.5, v3, v2

It'd be great to be able to use this for unit tests. Specifically, I think support for NUnit and XUnit would be very useful.

Set Culture of the thread to the same as the browser.
This way the client gets the same date formating as his computer..

I almost always want System, Linq, Collections, Generics and a few others in "using" clauses. I think they should be added to the blank default program, or maybe add a button to add them so I don't have to enter them manually.

Include the UnityEngine Library so we can test Unity C# scripts.

Add Support shortcuts for build and e.g. like in Visual Studio