OmniSharp Stop Working with Odd Multi-Byte characters

Environment data

dotnet --info output:NET Command Line Tools (1.0.0-preview2-002864)/windows 10-10586-x64
VS Code version:1.20
C# Extension version:1.0.11

Steps to reproduce

1. open a solution
2. type some code like below, with odd Chinese characters

ExceptionHelper.ThrowIfTrue(userId==entity.uid, "uid", "不存在");

1. reopen the solution, it works(showing references, definitions ...)
2. in the same file, OmniSharp will not work when you type any code

   Expected behavior

   OmniSharp works well with any characters

Actual behavior

OmniSharp stop working

[DustinCampbell]

I suspect this will be addressed with OmniSharp/omnisharp-roslyn#598.