system.valueuple reference?

[newyhj]

runtime:.net framework 4.8

var result= DbContext.FetchMultiple<int, int, int, int>(
"select count(id) from zm_article where siteid=@0;select count(id) from zm_product where siteid=@0;select count(distinct(email)) from zm_enquiry;select count(id) from zm_member", siteId);
return new SiteStatistics
{
SiteId = siteId,
ArticleCount = result.Item1.FirstOrDefault(),
ProductCount = result.Item2.FirstOrDefault(),
EnquiryCount = result.Item3.FirstOrDefault(),
MemberCount = result.Item4.FirstOrDefault()
};

vs:

already nuget install system.valuetuple 4.6.0,how to fix?