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After switching to a new Windows PC I keep getting these iOS build errors during compilation:
error CS8137: Cannot define a class or member that utilizes tuples because the compiler required type 'System.Runtime.CompilerServices.TupleElementNamesAttribute' cannot be found. Are you missing a reference?
error CS8179: Predefined type 'System.ValueTuple`2' is not defined or imported
Installing package System.ValueTuple does not help.
See also: https://developercommunity.visualstudio.com/content/problem/55133/xamarinios-cannot-resolve-systemvaluetuple.html
Problem is fixed after manually adding this reference: nuget\packages\system.valuetuple\4.3.1\lib\portable-net40+sl4+win8+wp8
This should not be necessary!
Some new info on the bug:
On my desktop PC (VS2017 Enterprise) I need to remove the reference otherwise it won't compile.
On my laptop (VS2017 Pro) I need to add the reference otherwise it won't compile.
In both cases same errors about Tuples.
Both running Xamarin iOS v10.10.0.30.
*** This bug has been marked as a duplicate of bug 56457 ***