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Can react native apps be displayed in a browser

I have a windows c# application for which I have previously developed a web client (HTML/JS) which accesses the shared data through an oData REST service.
I am now looking to move the entire application to a single platform across all devices. This will be native to iOS and Android, but I am looking to share code as much as possible. I am not interested in hybrid apps.
The two viable options are Xamarin and React Native. Although I hate Javascript, I am leaning towards React, simply because of momentum - the xamarin team seems to be very small and there is not a lot of evidence of extensive support for the xamarin platform from within microsoft.
My concern with React is - although it seems that it will get the job done on iOS and Android, it is not clear how you can run applications on PC/Mac. I am aware there is UWP / WPF support but am unsure if this is of any quality. I expect the best solution would be to run it in a browser on non-mobile platforms.
Is this possible with React Native, and is it something you could use in production in the foreseeable future.

Microsoft ReactXP is exactly what you are looking for.
Although it is still very young (first release at 22 Apr, 2017), Nader Dabit did some really excellent works on it.
Video Tutorial Here

How to make the headphones hear the microphone in C# (not streaming)

Windows Sound mixer/settings can set the microphone to play over the speakers. I'm looking for a way to do that through C#. I'm assuming there is a DLL reference or .NET call that might be able to.
Everything I've been finding invariably goes back to streaming, which I don't want to do. Unless that's whats actually happening under the hood when changing the audio settings in windows.
If it helps, I'm using C# 3.5 (Unity App) and running on Windows 10 latest.
Thanks!

You can do this with Core Audio APIs link
For implementation you can refer
https://blog.sverrirs.com/2016/02/windows-coreaudio-api-in-c.html

Create non UWP apps in C# and XAML?

Short backstory, I need to create an App for my computing coursework, and since I'm quite the procrastinator I wanted to make an app that shuts down processes that users waste time on.
Therefore I looked up how to make Windows 10 apps and stumbled across Microsoft's own "C# Fundamentals for Absolute Beginners" and "Windows 10 Development" for absolute beginners. I spent over 20 hours watching these videos over the past few weeks.
Now I have designed nearly all the UI in XAML over the past few days and now when working on the Code behind in c# I noticed that System.Diagnostics.Process could not be found, I tried to work out why and eventually stumbled across this answer which made my jaw drop (TLDR it's because it's a UWP app): Missing reference to System.Diagnostics.Process
I do not need my app to run on the Windows Store, all it needs to run on is my computer however messy the solution may be, but I really need access to that class to shutdown processes. I really want to make the app in C# and XAML though and I'm not sure if I can do this whilst having access to the System.Diagnostics.Process class.
I am really running out of time for this project and I can't just change my idea as the problem definition essay has already been marked, etc and that would take forever to rewrite.
I am open to the idea of just writing the application fully in C# if there's really no way I can use XAML without making a UWP app. But I'm not sure what's the easiest way of doing this/what project type so any help would be appreciated.
I feel very angry at Microsoft for not making it clear that "Windows 10 Development for absolute beginners is" actually "Windows Store Development for absolute beginners". I do not want my app on the Windows Store so if I could force reference the process class that would be great!

You need to develop a Desktop app (WPF). With WPF you also use C# and XAML, however you can use all .Net Framework.
UWP (Store apps) need to run in devices like Surface RT (Windows RT), Lumia 920 (Windows 10 Mobile), XBOX and Hololens so they use only a part of the full .Net Framework (they use the .Net Core Framework). UWPs run in a sandboxing so they usually don't have access to system APIs (low level access like create a IP package). In this case you should use WPF.
Your problem is one of the reason, I think that StackOverflow use the tag uwps and win-universal-app.

.net 3.5 windows form application, using webcam

Having searched high and low for native c# hook to webcam, I found 5 basic ways to interact with the camera.
Video for Windows (VFW)
DirectX
avicap32.dll
WIA
3rd party tools
My requirement is to take a photo. The application will be used on some legacy windows XP and Vista machines, but going forward Windows 7 and greater will be required. So what might the best approach be with the broad install base? Just reading WIA looked like the way to go but looks like some changes were made so it works a little different now (I don't know for sure). I understand that some people have done combos.
Might need to crop photo, but that is really about it.
For school visitor monitoring.

I think the best thing is to use the WIA. I know a third party toolkit that could help you doing your requirements which is leadtools. You can check this Tutorial

I would always try to pick up something already on the web and tweak it to my own needs... some open source project or an example where the mainly portion of my app is already made.
on Codeplex you can find a nice library to work with webcams and it's simply called
WebCam Library for WinForm and WPF with C# and VB.NET
Give that a try, maybe you can even help the project, by contributing your own findings, and everyone is a winner... isn't Open Source a great idea?!

Ideas for a C# UI framework

I need to develop a C# touch-screen desktop application with a "modern good-looking" UI.
How would you approach it? I´ve got in mind using Flash (just for the UI) or WPF... but i´m open to any idea or any third-party C# UI you´d know.
Is Flash easy to integrate with C#?
Thanks for your knowledge!

You should look for a AMF remoting library in C#.
Remoting is when you call a function on your server from flash.
AMF (version 0 or 3) is a binary format used to encode object transfered
between client and server
Weborb and fluorine are solutions for this.
see : .NET and AMF

You will probably be doing well with a third party framework to avoid the overhead of writing user interactions, controls, etc.
A couple of options are
http://xamarin.com/
http://www.resco.net/developer/mobileformstoolkit/
A review of these options is provided here.

I recall combining a flash interface with a C# back-end back in university. There's a method called fscommand() that will take a couple of string parameters (I may be mistaken, read up on it) to pass to and from the interface and the C# "code-behind".Flash is an ok option, but if I were you I'd opt for a WPF interface. I'm a huge fan of the telerik libraries, their WPF one allows you to create the most modern-looking interfaces and dashboards. Not to mention that the skills you will acquire while learning enough about wpf will be hugely beneficial in your career as a developer the way things are going (depending, obviously, on what direction you're heading).

FlashBuilder 4.6 has some nice functionality for quickly building a UI that work on a desktop or mobile device. You could use FluorineFX (free) or webOrb on a webserver to send data back and forth to a database server if that were needed. If you build it with the Flashbuilder 4.6 mobile project template, it would work on a iPad, mac, windows pc, or android device as well. Since a pc touchscreen should use the same type of finger gestures as a mobile app, this might be a nice way to go. (I don't actually have a touchscreen on my pc, but it runs well with a mouse, so I'd assume it worked with gestures too).
Adobe.tv has lots of examples of building a mobile app project (Which also runs on a PC) and there is a Flashbuilder 4.6 free trial.
http://flex.org/