OmniSharp server throws System.IO.FileNotFoundException: Could not load file or assembly 'netstandard, When Opening Unity Project

Question

I've updated my Visual Studio Code this morning, after doing update it restarted it self. I did not get any options(i.e. "Goto Definition", "Rename Symbol")when I right click on any variable, method, class name. After searching for a while I found that Opening View > Output might help me to know what's going on. and I found Omniserver is not running and below is the error which I got in Output window.

Starting OmniSharp server at 4/17/2019, 2:42:04 PM
    Target: d:\projects\Division\Division.sln

OmniSharp server started.
    Path: C:\Users\Unity3\.vscode\extensions\ms-vscode.csharp-1.19.0\.omnisharp\1.32.18\OmniSharp.exe
    PID: 7508

System.IO.FileNotFoundException: Could not load file or assembly 'netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' or one of its dependencies. The system cannot find the file specified.
File name: 'netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'
   at OmniSharp.Stdio.Driver.Program.<>c__DisplayClass0_1.<Main>b__1()
   at OmniSharp.HostHelpers.Start(Func`1 action)

=== Pre-bind state information ===
LOG: DisplayName = netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51
 (Fully-specified)
LOG: Appbase = file:///C:/Users/Unity3/.vscode/extensions/ms-vscode.csharp-1.19.0/.omnisharp/1.32.18/
LOG: Initial PrivatePath = NULL
Calling assembly : Microsoft.Extensions.Logging.Abstractions, Version=2.1.1.0, Culture=neutral, PublicKeyToken=adb9793829ddae60.
===
LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\Users\Unity3\.vscode\extensions\ms-vscode.csharp-1.19.0\.omnisharp\1.32.18\OmniSharp.exe.Config
LOG: Using host configuration file: 
LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework64\v4.0.30319\config\machine.config.
LOG: Post-policy reference: netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51
LOG: Attempting download of new URL file:///C:/Users/Unity3/.vscode/extensions/ms-vscode.csharp-1.19.0/.omnisharp/1.32.18/netstandard.DLL.
LOG: Attempting download of new URL file:///C:/Users/Unity3/.vscode/extensions/ms-vscode.csharp-1.19.0/.omnisharp/1.32.18/netstandard/netstandard.DLL.
LOG: Attempting download of new URL file:///C:/Users/Unity3/.vscode/extensions/ms-vscode.csharp-1.19.0/.omnisharp/1.32.18/netstandard.EXE.
LOG: Attempting download of new URL file:///C:/Users/Unity3/.vscode/extensions/ms-vscode.csharp-1.19.0/.omnisharp/1.32.18/netstandard/netstandard.EXE.

[ERROR] Error: OmniSharp server load timed out. Use the 'omnisharp.projectLoadTimeout' setting to override the default delay (one minute).

Answer 1

I had the same problem with Omnisharp v1.19.0 after updating VSCode. I ended up resolving it by rolling back the C# extension to an earlier version that worked for me (1.18.0). Right click the extension and select Install Another Version... Hope this helps!

Answer 2

The rollback to 1.18.0 worked for me, but be sure to set the preference "extensions.autoUpdate" to false or it will just reinstall 1.19.0