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?