# Mono

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From Wikipedia:

  Mono is a [...] project to create a .NET Framework-compatible set of tools including, among others, a C# compiler and a Common Language Runtime.

## Installation

Install the mono package.

If you need VisualBasic.Net support you have to install the VisualBasic.Net interpreter with the package mono-basicAUR.

MonoDevelop calls xterm when you run your project. You might install it, when you are writing a console application.

Note: Installing the package stores certificate authorities in `/usr/share/.mono/certs/Trust/` but removing the package does not remove them.[1]

## Running Mono applications

You can execute Mono binaries by calling `mono` manually:

    $ mono programsname.exe

You can also execute Mono binaries directly, just like native binaries:

    $ chmod 755 exefile.exe
    $ ./exefile.exe

## Testing Mono

Make a new file:

    test.cs

    using System;

    public class Test {
     public static void Main(string[] args) {
      Console.WriteLine("Hello World!");
     }
    }

Then run:

    $ mcs test.cs
    $ mono test.exe
    Hello world!

## Development

Starting to develop in Mono/C# is very easy. Just install the MonoDevelop IDE with package monodevelop-stableAUR or monodevelop-gitAUR. Alternatively, you can install the riderAUR IDE.

If you want the API documentation browser and some testing and development tools you have to install mono-tools.

## Troubleshooting

### I get an error "cannot execute "path/to/your/binary" file name has not been set."

You might install xterm, since MonoDevelop starts xterm when you press on run. This might be a possible dependency.

### I get an error when I try to run Mono binaries directly: "cannot execute binary file"

The binfmt_misc handler for Mono has not yet been set up, as explained in detail on the Mono Project website.

To fix this, restart the `systemd-binfmt` service.

### I get an TLS handshake (or similar certificate based) error

Try `mozroots --import --ask-remove` which should update monos certificates. `mozroots` is part of the mono package.

### I get an error when building fsharp: "System.TypeInitializationException: The type initializer for 'System.Console' threw an exception"

There is a recent bug in mcs that is used to build fsharp. A workaround is to use `export TERM=xterm`, as detailed here [2]

## See also

- Official Mono website
- The Mono Handbook
- The API reference of Mono
- ECMA-334: C# Language Specification
- ECMA-335: Common Language Infrastructure (CLI)
- Instructions for running Mono applications

Category:

- Frameworks