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Troll coworkers - use Emacs at work for csharp!
Emacs Lisp Cucumber Shell

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omnisharp-emacs is a port of the awesome OmniSharp server to the Emacs text editor. It provides IDE-like features for editing files in C# solutions in Emacs, provided by an OmniSharp server instance that works in the background.

This requires the OmniSharp Server program

The server must be at least the following version (expect this to be update to this guide whenever the required version changes):

Date:   Sat Oct 18 23:08:19 2014 +0100

If you haven't updated your server copy since that, you must upgrade.

Project maturity

Lacks a better UI and a good default configuration.


  • Contextual code completion (i.e. auto-complete / IntelliSense) using popup.el or ido-mode or company-mode if it is installed. Currently popup and ido-mode can complete symbols in all namespaces if so configured.
    • Popup.el and company-mode provide a more sophisticated interface, with the possibility to fall back on all of ido's flexible matching power.
    • Also shows documentation like other IDEs
  • Show type of the current symbol in the minibuffer. With prefix argument, add it to kill ring. Optional eldoc support available to show this automatically when point is on a symbol (see the source for help)
  • Navigation helpers
    • Go to definition of a type/variable/method etc. With the prefix argument (C-u), use another window.
      • Find usages of the current symbol in the solution
      • Find implementations/derived types of the current type
      • Go to definition of a type in the current file with ido-mode (fast).
      • Go to definition of a member in the current type with ido-mode (likewise fast :)).
      • Go to region / endregion in current file
      • Go to any member in the solution (property, method etc.)
      • Go to file, then go to member (type, property, method) in that file.
  • Rename the current symbol and all references to it
    • Rename only semantic references ("smart" rename)
    • Rename as verbatim text ("dumb" rename)
  • Solution manipulation
    • Add/remove the current file
    • Add/remove selected files in the dired directory editor
  • Override selected superclass member
  • Run a refactoring on the current position
    • Uses the refactorings from the NRefactory library, which is also used by the MonoDevelop and SharpDevelop IDEs
    • When used with a selection, prompts to extract a method from the selection where possible
  • Solution building
    • The user may choose whether they want to build in the emacs *compilation* buffer or at OmniSharp's end (non-asynchronous, that is, blocking)
    • Jump to errors like in normal *compilation* output
  • Format the current buffer
    • Currently only one formatting style supported, easy to add more.
  • Fix using statements
    • Sorts, removes and adds any missing using statements for the current buffer
  • Syntax checker for parse errors
    • Runs using the provided Flycheck checker in the background.
  • Syntax checker for code issues (refactoring suggestions)
    • This automatically runs when there are no syntax errors
    • Fix the first suggested error on the current line with omnisharp-fix-code-issue-at-point
  • OmniSharp server instance manipulation
    • Start server
    • Reload solution
    • Stop server
  • Test runner
    • Can run test at point, fixture or all tests in project.



company-mode interface

company-mode showing parameters and return values, and the selected function description in the minibuffer. As you can see, the completion works with non-trivial code.

Pressing F1 with a candidate selected in the the company-mode popup shows a buffer with documentation.

Omnisharp's company-mode support ignores case by default, but can be made case sensitive by setting omnisharp-company-ignore-case to nil.

popup.el interface

popup.el with documentation. The documentation may be disabled if you need the screen space. There is an option to show documentation in a help buffer.

To (not) complete from all namespaces, use the prefix argument when calling. This inverts the omnisharp-auto-complete-want-importable-types setting temporarily.

Ido interface

Ido allows for flexible matching of all text that the completions have. Each pressed character will narrow the list down to fewer options. It's also possible to do a cross search at any point with a new search term by pressing C-SPC.

This makes it really easy to e.g. narrow the list down to members that handle a specific type, such as bool.

To (not) complete from all namespaces, use the prefix argument when calling. This inverts the omnisharp-auto-complete-want-importable-types setting temporarily.

Go to type in current file

This is a standard functionality in e.g. Visual Studio. The types are shown in the order they occur in the source file.

Go to member in current type

This too is standard in various IDEs. Using ido makes navigating fast and intuitive. The members too are shown in the order they occur in the source file.


Renaming suggests the current type as a basis.

Overriding members

When invoked, displays a list of possible override targets.

When a target is chosen, a stub member is inserted.

Refactoring suggestions

For now, this must be manually invoked. It can do different things depending on the symbol under point. In this picture it has been invoked on a method parameter.

Solution building

Here is an example of an asynchronous build within Emacs. It works by getting the build command from the backend and executing that in the compilation buffer.

Syntax errors checking

It is possible to check the current buffer for syntax errors using the flycheck library. This is done asynchronously, and errors are shown when found. Note that this is not a type checker, only syntax is currently checked.

To start the check, use (flycheck-mode) or select it in the menu. The check will then be performed after the current buffer has been idle for a certain number of seconds or when it is saved, depending on your flycheck configuration.

To make syntax checking start sooner/later, use:

(setq flycheck-idle-change-delay 2) ; in seconds

ElDoc integration

ElDoc support is switched on by default. This shows type information for the symbol at point in the echo area. To switch it off, set omnisharp-eldoc-support to nil.

Imenu integration

Omnisharp's Imenu support allows you to quickly view and jump to function and variable definitions within your file. This can be used either natively or in combination with helm-imenu Imenu support is off by default, but can be turned on by setting omnisharp-imenu-support to t

Helm integration

If you have Helm installed, Omnisharp offers several integrations. First of all, there's helm-imenu:

There's also 'omnisharp-helm-find-usages', which allows you to easily navigate to references in your project:

And then there's 'omnisharp-helm-find-symbols', which allows you find and jump to any symbol in your project:

company-mode integration

To enable company-mode autocompletion, omnisharp requires at least version 0.7 of company-mode to be installed. Then add the following to your init file:

(eval-after-load 'company
  '(add-to-list 'company-backends 'company-omnisharp))

company-mode completion will only trigger when omnisharp-mode is active.

Test runner integration

Can run the test at point, fixture at point, or all tests in project.

Specify the path and parameters to your test runner on the server here :-


This supports Emacs 24.3 and above at least. It has been tested on Ubuntu 12.04 (Precise), on Windows 7 and on OSX.

To install, use MELPA. After MELPA is installed, use

M-x package-install omnisharp RET

to install.

omnisharp-emacs depends on the external program curl for accessing the background OmniSharp server process. You need to ensure this is installed and can be found by Emacs. On Windows you should install the native curl program from the curl website.

To make sure omnisharp-emacs can find your curl, make your PATH environment variable contain the directory for curl, or set the omnisharp--curl-executable-path variable to the full path to the curl executable. The path may be e.g. "C:\Program Files (x86)\Git\bin\curl.exe" or /usr/bin/curl.

To automatically load omnisharp-emacs when editing csharp files, add something like this to your csharp-mode-hook:

(add-hook 'csharp-mode-hook 'omnisharp-mode)

Start an OmniSharp server process on a solution, and you should have access to all of this program's functions. To do this, you can use M-x omnisharp-start-omnisharp-server and navigate to a solution file. This will start the server and let emacs handle the server process's life.

If you want to start the process externally so it's not killed when emacs is closed, see the instructions at OmniSharp.

You probably need to create a custom configuration for accessing omnisharp-emacs in your normal coding sessions. There is an example configuration for evil-mode included in the project.

Using Cygwin on Windows?

Cygwin paths need to be converted on the server side for the OmniSharp server to handle them correctly. See the server side configuration file config-cygwin.json that has example configuration for Cygwin environments and use the example path replacements by renaming that file to config.json.

Pull requests welcome!

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