#+TITLE: C# layer

#+TAGS: general|layer|multi-paradigm|programming

[[file:img/csharp.png]]

* Table of Contents                     :TOC_5_gh:noexport:
- [[#description][Description]]
  - [[#features][Features:]]
- [[#backends][Backends]]
- [[#install][Install]]
  - [[#omnisharp-backend][Omnisharp backend]]
- [[#caveats][Caveats]]
- [[#key-bindings-for-the-omnisharp-backend][Key bindings for the omnisharp backend]]
  - [[#navigation][Navigation]]
  - [[#helpers-documentation-info][Helpers (documentation, info)]]
  - [[#refactoring][Refactoring]]
  - [[#omnisharp-server-interaction][OmniSharp server interaction]]
  - [[#tests][Tests]]

* Description
This layer adds support for the C# language using the [[https://github.com/OmniSharp/omnisharp-roslyn][omnisharp-roslyn]]
language server with either the [[https://github.com/OmniSharp/omnisharp-emacs][omnisharp-emacs]]
or the [[https://github.com/emacs-lsp/lsp-mode][lsp-mode]] packages.

** Features:
- Syntax checking with flycheck (when =syntax-checking= layer is used)
- Support for auto-completion (when =auto-completion= layer is used)
- Refactoring
- Navigation to cross-references
- Inspecting types in metadata

* Backends
There are two backends available for this layer, one based on the =omnisharp-emacs=
package and a new one based on =lsp-mode= (language server protocol) package.

Both backends use the omnisharp-roslyn server under the hood however different
features are available. The =omnisharp= backend might be more stable at this 
moment (late 2019).

* Install
To use this configuration layer, add it to your =~/.spacemacs=. You will need to
add =csharp= to the existing =dotspacemacs-configuration-layers= list in this
file.

You can also choose between one of the two available backends by setting 
the =csharp-backend= variable when configuring the layer:
- =omnisharp= (the default), or
- =lsp= (testing)
- =nil= (to not use any language server)

To use the lsp backend, add `csharp' layer with =csharp-backend= variable set to 'lsp:

#+BEGIN_SRC elisp
  (csharp :variables csharp-backend 'lsp)
#+END_SRC

** Omnisharp backend
Before you can work with C# files you will need to install the server by invoking
~SPC m s i~ (or =M-x omnisharp-install-server=). Otherwise, if this fails for you, please see
[[https://github.com/OmniSharp/omnisharp-emacs/blob/master/doc/server-installation.md][omnisharp-emacs/doc/server-installation.md]].

While the server will start automatically it may still be required for you to start
it manually using ~SPC m s s~ (or =M-x omnisharp-start-omnisharp-server=). It will 
prompt a path to your .csproj or .sln file.

* Caveats
- You should use =dotnet= CLI tool from [[https://www.microsoft.com/net/download/core][.NET Core download page]] or an IDE like
  Visual Studio or Xamarin Studio to manage solution and project files.
- Debugging on command line is possible using [[https://github.com/mono/sdb][SDB]].
- There can be *only one server* running at the same time using the =omnisharp= backend.
  To switch to a different solution/project you need to invoke ~SPC m s S~ and ~SPC m s s~ to stop
  current server and start another one pointing to another solution/project.
- LSP backend supports multiple concurrent language servers/projects loaded.

* Key bindings for the omnisharp backend
The following key bindings are available when using the =omnisharp= backend.
LSP-backend uses key bindings that are common for all layers/languages using the =lsp= layer.

** Navigation

| Key binding | Description                                   |
|-------------+-----------------------------------------------|
| ~SPC m g c~ | Go to member in current file                  |
| ~SPC m g e~ | List errors and warnings in solution          |
| ~SPC m g f~ | Go to solution file                           |
| ~SPC m g F~ | Go to solution file then member               |
| ~SPC m g g~ | Go to definition                              |
| ~SPC m g G~ | Go to definition in other window              |
| ~SPC m g i~ | Find implementations                          |
| ~SPC m g I~ | Find implementations using ido                |
| ~SPC m g m~ | Go to solution member                         |
| ~SPC m g M~ | Go to solution member in other window         |
| ~SPC m g r~ | Go to region                                  |
| ~SPC m g s~ | Find symbols using Helm                       |
| ~SPC m g u~ | Find usages of symbol under cursor using Helm |
| ~SPC m g U~ | Find usages of symbol under cursor using ido  |

** Helpers (documentation, info)

| Key binding | Description                                                            |
|-------------+------------------------------------------------------------------------|
| ~SPC m h t~ | Get type information for symbol under cursor                           |
| ~SPC m h T~ | Get type information for symbol under cursor and put it into kill-ring |

** Refactoring

| Key binding | Description                              |
|-------------+------------------------------------------|
| ~SPC m r m~ | Rename symbol under cursor               |
| ~SPC m r M~ | Rename symbol under cursor interactively |
| ~SPC m r r~ | Refactor under cursor                    |

** OmniSharp server interaction

| Key binding | Description                |
|-------------+----------------------------|
| ~SPC m s i~ | Install OmniSharp server   |
| ~SPC m s r~ | Reload the solution        |
| ~SPC m s s~ | Start the OmniSharp server |
| ~SPC m s S~ | Stop the OmniSharp server  |

** Tests

| Key binding | Description                      |
|-------------+----------------------------------|
| ~SPC m t b~ | Run tests in current buffer      |
| ~SPC m t t~ | Run the last executed test again |
| ~SPC m t t~ | Run the test around point        |