Could not load type 'System.Runtime.CompilerServices.ExtensionAttribute' from assembly 'mscorlib

Question

When starting up my web site for the first time, I\'m getting this error

Could not load type \'System.Runtime.CompilerServices.ExtensionAttribute\' from assemb

Answer 1

In my case, it was Blend SDK missed out on TeamCity machine. This caused the error due incorrect way of assembly resolving then.

Answer 2

We ran into this problem and tracked it down to the Geocoding.net NuGet package that we were using to help with our Google Maps views (Geocoding.net version 3.1.0 published 2/4/2014).

The Geocoding dll appears to be .Net 4.0 when you examine the package file or view it using Jet Brains’ Dot Peek application; however, a colleague of mine says that it was compiled using ilmerge so it is most likely related to the ilmerge problems listed above.

It was a long process to track it down. We fetched different changesets from TFS till we narrowed it down to the changeset that added the aforementioned NuGet package. After removing it, we were able to deploy to our .NET 4 server.

Answer 3

In my case I had an issue around using Microsoft.ReportViewer.WebForms. I removed validate=true from add verb line in web.config and it started working:

<system.web>
    <httpHandlers>
      <add verb="*" path="Reserved.ReportViewerWebControl.axd" type="Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />

Answer 4

Just adding this answer to help Google save some punter the hours I have spent to get here. I used ILMerge on my .Net 4.0 project, without the /targetplatform option set, assuming it would be detected correctly from my main assembly. I then had complaints from users only on Windows XP aka WinXP. This now makes sense as XP will never have > .Net 4.0 installed whereas most newer OSes will. So if your XP users are having issues, see the fixes above.

Answer 5

I had this problem, except the type it couldn't load was System.Reflection.AssemblyMetadataAttribute. The web application was built on a machine with .NET 4.5 installed (runs fine there), with 4.0 as the target framework, but the error presented itself when it was run on a web server with only 4.0 installed. I then tried it on a web server with 4.5 installed and there was no error. So, as others have said, this is all due to the screwy way Microsoft released 4.5, which basically is an upgrade to (and overwrite of) version 4.0. The System.Reflection assembly references a type that doesn't exist in 4.0 (AssemblyMetadataAttribute) so it will fail if you don't have the new System.Reflection.dll.

You can either install .NET 4.5 on the target web server, or build the application on a machine that does not have 4.5 installed. Far from an ideal resolution.

Answer 6

In my case after downgrading from .NET 4.5 to .NET 4.0 project was working fine on a local machine, but was failing on server after publishing.

Turns out that destination had some old assemblies, which were still referencing .NET 4.5.

Fixed it by enabling publishing option "Delete all existing files prior to publish"