U4-11441 - Build error when upgrading v7.7.4 -> v7.10.4: Assembly with the same identity System.ValueTuple has already been imported

Created by Viktor Ekholm 14 Jun 2018, 13:27:39 Updated by Sebastiaan Janssen 14 Jun 2018, 13:45:53

When upgrading from v7.7.4 to v7.10.4 I got this error on my TeamCity build server:

{{[Csc] c:\BuildAgent2\work\77aab30cc95edb67\packages\System.ValueTuple.4.4.0\lib\net47\System.ValueTuple.dll error CS1703: An assembly with the same identity 'System.ValueTuple, Version=, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' has already been imported. Try removing one of the duplicate references.}}

I traced the problem to this configuration in my web .csproj file:


Which comes from the UmbracoCms.Core project. packages.config references System.ValueTuple v4.4.0, but it seems weird that the reference named v4.0.2.0 points to the NuGet package version of v4.4.0. When I change the reference my build server is happy again.

Intended or not?


Viktor Ekholm 14 Jun 2018, 13:40:40

PR: https://github.com/umbraco/Umbraco-CMS/pull/2697

Sebastiaan Janssen 14 Jun 2018, 13:45:47

Thanks @vikekh - unfortunately that's not the solution (see the PR for details). Unfortunately I haven't seen this specific error before. Google suggests you delete references to System.ValueTuple in your projects and add them again.

For more help make sure to head on over to the forums and see if someone else has had this problem. https://our.umbraco.org .

Priority: Normal

Type: Bug

State: Closed


Difficulty: Very Easy

Category: Installation

Backwards Compatible: True

Fix Submitted:

Affected versions:

Due in version:


Story Points: