Develop Reference

Can I connect to database with another language

Hi i have a C# WinForms app. I wrote essential methods on C#. But I need a login form and its not safe since apps like dotpeek can inspect the source code and hack it. Can i communicate with another application that is written in another language (java,c,python etc). I need to send input data from WinForms C# to another app then it should connect to database and check if login succesfull then return a value back to C# WinForms app. Is that possible, how can i implement that? I dont want to write all application in another language since C# has good methods to process images/pixels and gui support with very small memory usage.

I got the point you are trying to make.
One thing to admit is that you can't completely avoid decompiling of apps. C# or C++, no matter anything can be reverse engineered.
If you still need it, a comparatively safer approach is to not put the checking app at the client's machine. Create an API and host the database on a server.
Then initiate just an Http Request to the server from your Windows Forms app.
Then you have the full control of Login API and database. Many applications use OAuth similar to this. Another examples are apps verify it's license using an online API.
You can get a LightSail Windows server in around $10 a month if you want to setup. Try exploring

Your concern is not baseless. C#, or for that matter, any .net language running on the CLR, will be easier to inspect than a language like C or C++.
Having said that, no app will be completely secure, and communicating between apps has its own problems. How does one app verify the other? etc. You can create a web service that would communicate with the database (and communicate with the web service using HTTP or WCF) which would mean your app wouldn't have direct access to the database, but that would only protect the database from your app, it would still allow someone to inspect your app and use the web service, impersonating your app. Also, you would need to host the web service on some web hosting service, and then you would have to trust that service to not inspect your app...
You can reduce the problem by storing the password etc. as byte arrays, but regardless of what you do, I don't know of a way to completely safeguard your app. If a malicious app/actor is on your computer they can inspect your app.
As for your question itself - look into WCF or named pipes (includes a simple example).

Interacting with an open application via web link [duplicate]

A few years back I developed a Silverlight Component called from within an ASP.net web app, that uses PInvoke to access a USB (Serial COM port) on the client machine to allow for sending commands to some scanner hardware.
With the advent of Windows 10 and the inevitable demise of Silverlight I am looking for alternatives to accessing hardware on the client PC (This is all Intranet Web Application stuff where we have a lot of control over the implementation)
Currently I am looking at Registering an Application to a URI Scheme (Easy solution) as per this page:https://msdn.microsoft.com/library/aa767914(v=vs.85).aspx
OR alternatively maybe Javascript navigator.msLaunchUri (This seems to not be supported in Windows 7, which we need to still support)
Refer: https://connect.microsoft.com/IE/feedback/details/864863/documented-api-function-navigator-mslaunchuri-not-present-in-windows-7
The Registering of an Application to a URI Scheme works fine in Windows 7/8/8.1 but seems to have changed in Windows 10 - Does anyone know how I can implement this (Through C# code, registry, something) to allow this to work in Windows 10

I recently wanted to just this as well - and I found the answer so i'm posting it here for future reference and I couldn't find a working example in C# anywhere.
First of all your app needs requireAdministrator permissions. To do this, right click on the project in the Solution Explorer and click Add New Item, then select General and finally Application Manifest file if you don't already have one. In there, change the requestedExecutionLevel to requireAdministrator. Save.
I this is the first time you've done this, you'll need to restart Visual Studio as it probably isnt running under Admin privaleges.
Okay, so I wanted my app to create the registry key when it starts up, so in the constructor for my form I put in the following code, which creates the URL Protocol foo:// for a program called 'oggsplit.exe' (which I happened to have in my C: root so I just used that for testing)
RegistryKey key;
key = Registry.ClassesRoot.CreateSubKey("foo");
key.SetValue("", "URL: Foo Protocol");
key.SetValue("URL Protocol","");
key = key.CreateSubKey("shell");
key = key.CreateSubKey("open");
key = key.CreateSubKey("command");
key.SetValue("", "C:\\oggsplit.exe");
Once you've configured that, save and run the program. You'll get no feedback, and as long as you don't see any errors it should have worked correctly. Now, open your browser (no need to restart or anything) and go to the address foo://hello. This is what it looks like for me in Google Chrome:
It will then ask you if you want to open your application from the browser, click okay. Hey Presto, your app opens from the browser, you can now put a specilised link into your web page to open your app from the browser. This Page also documents how to pass arguments through to your program as well.

In win10 you can try to use URI handlers. There should be Package.appxmanifest file where you can list URIs that should launch your app.
Also, I found interesting the folowing article that describe web-to-app approach for various OS

How to create a public server in C#

I am a novice programmer. I was trying to learn about networking in C#. I want to know how to create a public server in C#. I tried to search on the internet but I didn't find much. As a public server, I meant to connect to one computer to another from remote or an online server where I can connect from anywhere which is written in C#. I want to know is how to make it and what I need to do that or especially I want the information how can I make one and what I need. I would like to use winform/wpf or console application for the server.(Sorry for my bad English)

There are plenty of resources out there already, you just need to do your research.
A couple notes:
winform/wpf is a technology for desktop programs, with windows and user controls and such. A server has no need for such things.
a server is a server, public or not. Making it public is as simple as making it available at an IP address / domain that is reachable from the internet. This has little to do with implementation.
there are so, so, so many different types of server applications. Some serve websites, others serve databases, and still others just provide raw data in the form of JSON or XML.
I'm assuming since you're just getting started, you're trying to build a web server to serve a website. Here's a tutorial I found by Googling 'c# web server' that seems to get you up and running: https://codehosting.net/blog/BlogEngine/post/Simple-C-Web-Server
Good luck, and remember that SO is a place for technical questions, not a 'how to do a whole thing start to finish' forum :)

I think the keywords you need are
ASP.NET + IIS, for a full fledged server app
HttpListener, for a stand alone server app
The prior is a framework for building a MVC Server application (it also has a subset called WebApi which as the name states is for APIs), and the latter is the class you will need to create a stand alone server application.
In the future, you might want to consider using ASP.NET Core to deploy your application onto linux.
Good luck.

How to properly execute C# file over local network?

Overview
C# File - Users PC
PHP Server - Hosts Webpages for application
Server and Users PC on local network
I have a c# file that reads weight from a USB scale. How would I trigger this file to run so it feeds into my program. The problem is I am using PHP to host our webpage/application so its not running client side and the scale is not hooked up to the server but to the clients PC.
The C# script would have to be on the clients in order to read the scale so how would I trigger this to happen?
Is this even possible and if not what would be a better way?
Important Edit
I was able to run the Scale Script (C#) when I wanted by having PHP and C# use TCP sockets.
The C# would listen for PHP to send something and when it did it would read the scale and send this information back to PHP becuase PHP was listening for a response. Mixed in with a little Ajax and it updates in the web browser.
Gave Chris Credit because he was the most helpful with answering my questions

It sounds like what you really want is for the client application to submit the data to the website itself, and the most suitable approach is probably to expose a web service from your server.
This service should accept weight data, along with some sort of customer key or whatever, to correlate the records correctly on the server side. I've never created a web service in PHP personally, so I can't give any advice on the implementation of that, but it is fairly trivial to hook a C# client app up to a web service once you've exposed its metadata (assuming you use SOAP).

you can't start C# application from a web page in a way that'll work in every browser every time. BUT, you can have some workarounds:
Use ActiveX component that read the data in the client and upload it to the server. the biggest cons is that it'll only work in Internet Explorer
use Silverlight client application that runs on elevated mode (v4) and upload the data to your server.
refer your clients to download application (the C# application you wrote about) and run it - this application will upload the data to your server.
hope this helps.

C# isn't a scripting language, it's a language that compiles into executable binaries or libraries. You won't be able to execute C# code on the client's computer via a website because C# code needs to be compiled before it can run.
Presumably what you really want is for your compiled C# binary to be executed on the client's machine via your website. You won't be able to easily do that. There are a lot of security measures in place to prevent browsers from running programs on your computer. There may be ways to hack around these security measures by using plugins (such as ActiveX), but it's not something that will be a one-liner.
Edit: I think you need to step back and think about what you're trying to do in a broad sense. You're trying to create a website that can read information from a user's USB port. This is the type of thing that browsers are designed to prevent, and for good reason. I wouldn't want random websites to be able to access peripheral hardware without my explicit permission. If you want this website to function the way you're expecting, you're going to have to seriously think about the security implications. You'll need some kind of client-side code (ActiveX, Silverlight, ...), and the user will need to explicitly give permission to for this all to happen. It won't be easy, and it won't be automatic. And I'm damn glad that's true.

How to start up your .NET program from web browser?

Could you provide example of JavaScript function for starting up application installed on your computer from a web browser (eg google chrome 4). It particular if .Net APPs have any special simplifying this process apis of out there are some libs for such staff, please share link with us.
so how to create and store in run on start up programs a small local server which would handel some local urls like http://localhost/maAppServer/MyAppCalculator/Start for starting apps that have written in its config file their names and local urls on install?
So how to start up your C# .NET app\program from web browser?

I don't believe its possible in Chrome, starting an EXE on a users computer could be considered a security violation. Some ActiveX, and file:// links in internet explorer may work. Also, OneClick deployment may do something similar to what you are after (not exactly though I don't think, and I believe they require an add-in which may not be available for Crhome) http://www.15seconds.com/issue/041229.htm

I'm not sure what you're asking for. You can start an application on your computer just by linking to it in the HTML page. However, if you need to pass data to it, then it's a different matter altogether, although it's still simple.
An example is what www.nexon.com does with it's MMORPG, MapleStory. You log on to the website, and the web page starts the game after the authentication. Another example would be the magnet links on file-sharing sites.
You need to create a protocol handler, it can be in any language like C++/C# and register it on the client's computer. Like so - http://msdn.microsoft.com/en-us/library/aa767914(VS.85).aspx
Then, just use the protocol you built to pass on whatever data necessary. You can add a link that can be clicked, a button, Response.Redirect() from the server, whatever you like.