Error:
C:\\WebApp\\WebApp.csproj : error : The SDK \'Microsoft.NET.Sdk.Web\' specified could not be found. C:\\WebApp\\WebApp.csproj
I agree with the comment on Sundeep's answer, you shouldn't have a global.json file in your project anymore.
It seems as though installing the .NET Core 2.0 SDK is causing issues with the PATH. Verify that C:\Program Files\dotnet and C:\Program Files (x86)\dotnet are in the PATH environment variable. In my case, these values were already present under System Variables so I added them to User Variables and rebooted my machine. This resolved my issue.