Consider the following code:

Console.WriteLine((  1, 2, 3, 4, 5, 6, 7, 8).GetHashCode());
Console.WriteLine((777, 2, 3, 4, 5, 6, 7, 8).GetHashCode()); // different result
		
Console.WriteLine((  1, 2, 3, 4, 5, 6, 7, 8, 9, 10).GetHashCode());
Console.WriteLine((777, 2, 3, 4, 5, 6, 7, 8, 9, 10).GetHashCode()); // same result

The ValueTuple ignores first N-8 fields when calculating hash code. It even says so in a comment in ValueTuple.cs. The offending code is:

if (size >= 8) { return rest.GetHashCode(); }

To be honest, this seems like a bug to me, since this behaviour is described nowhere but the source. We were using tuple syntax to calculate hash codes of several class members and just noticed, that even with some fields changed, the hashes were still equal.. I understand this will have performance implications, but still I find the GetHashCode() unusable in its current state for "big" tuples. This is wrong for both .NET Framework and Core.