I have a very small, simple ASP.NET MVC app (MVC 4 I think. .NET Framework 4) it consists of one controller with one action serving one page.
I'm deploying it on AppHarbor, pushing it with git on my local machine, I've never had problems running it locally and it has never had build issues/errors on AppHarbour but every now and then a new build (with no relevant change in my mind) will start throwing the following error:
Could not load file or assembly 'Microsoft.Threading.Tasks, Version=1.0.12.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.
Looking into this the top answer here sorted it, I removed the dependent assemblies listed and it worked again. But then it came back. Tried a lot of different suggestions, it has always used nuget, tried removing everything and re-installing, it started working again when I wasn't even sure what I'd changed and now it isn't working again. Today I switched it to NuGet Package Restore as outlined here but that hasn't made any difference.
I can re-deploy the last working build, what I notice comparing working/not working builds downloaded from AppHarbor is that the Web/App.configs are identical (no dependent assembly entriy for this) but the Microsoft.Threading.Tasks dlls and xmls (including Extensions and Extensions.Desktop) are not in the broken build (in the working build they appear in the root and in the bin)?
In the project the dlls are linked from the packages folder for the app and Copy Local is True, they aren't a direct dependency of the Web App but of the Google Calendar API its using.
Update On the back of writing the answer I've looked more closely at the build logs and noticed a distinct difference between a working and not-working build.
The Microsoft.Threading.Tasks.dll is not a direct dependency, its required by Google.Apis.Gmail.v1.dll, in a working build the build log will contain (see the bottom line copying Microsoft.Threading.Tasks.dll):
\Google.Apis.Gmail.v1.dll". Copying file from "D:\temp\voz3srsa.vhb\input\TwitterBot\packages\Google.Apis.1.9.0\lib\net40\Google.Apis.PlatformServices.dll" to "D:\temp\voz3srsa.vhb\output\Google.Apis.PlatformServices.dll". Copying file from "D:\temp\voz3srsa.vhb\input\TwitterBot\packages\TweetSharp.2.3.1\lib\4.0\Hammock.ClientProfile.dll" to "D:\temp\voz3srsa.vhb\output\Hammock.ClientProfile.dll". Copying file from "D:\temp\voz3srsa.vhb\input\TwitterBot\packages\log4net.2.0.3\lib\net40-full\log4net.dll" to "D:\temp\voz3srsa.vhb\output\log4net.dll". Copying file from "D:\temp\voz3srsa.vhb\input\TwitterBot\packages\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.dll" to "D:\temp\voz3srsa.vhb\output\Microsoft.Threading.Tasks.dll".
A not-working build will have a different dll in its place (see the bottom line again, Microsoft.Web.Infrastructure.dll):
\Google.Apis.Gmail.v1.dll". Copying file from "D:\temp\0kzqakoc.4jo\input\TwitterBot\packages\Google.Apis.1.9.0\lib\net40\Google.Apis.PlatformServices.dll" to "D:\temp\0kzqakoc.4jo\output\Google.Apis.PlatformServices.dll". Copying file from "D:\temp\0kzqakoc.4jo\input\TwitterBot\packages\TweetSharp.2.3.1\lib\4.0\Hammock.ClientProfile.dll" to "D:\temp\0kzqakoc.4jo\output\Hammock.ClientProfile.dll". Copying file from "D:\temp\0kzqakoc.4jo\input\TwitterBot\packages\log4net.2.0.3\lib\net40-full\log4net.dll" to "D:\temp\0kzqakoc.4jo\output\log4net.dll". Copying file from "D:\temp\0kzqakoc.4jo\input\TwitterBot\packages\Microsoft.Web.Infrastructure.1.0.0.0\lib\net40\Microsoft.Web.Infrastructure.dll" to "D:\temp\0kzqakoc.4jo\output\Microsoft.Web.Infrastructure.dll".
Looking into dlls missing in the build I found this answer but I have tried a command prompt build locally and it works fine.
Update 2 Also in trying to solve this I had noticed a comment on the build (not a warning) around reference versions:
1> Consider app.config remapping of assembly "Newtonsoft.Json, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed" from Version "4.5.0.0" [C:\Users...\packages\TweetSharp.2.3.1\lib\4.0\Newtonsoft.Json.dll] to Version "6.0.0.0" [C:\Users...\packages\Newtonsoft.Json.6.0.6\lib\net40\Newtonsoft.Json.dll] to solve conflict and get rid of warning. 1>C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets(1605,5): warning MSB3247: Found conflicts between different versions of the same dependent assembly.
Couldn't get a remapping that sorted it but did get this where adding an app.config (which makes no sense for a web app) redirect fixed it where the redirect in the web.config didn't. This did stop the build issue but made little sense.
