I've installed dotnet core 3 sdk and OmniSharp 1.18 extension on VSCode but OmniSharp has an error: Microsoft.Build.Exceptions.InvalidProjectFileException: The SDK 'Microsoft.NET.Sdk.Web' specified could not be found.
Try the workaround solution bellow:
Add a file called omnisharp.json to your project folder with following content
{
"MsBuild": {
"UseLegacySdkResolver": true
}
}
Then restart the Visual Studio Code