Can not find "System.Security.Cryptography.Xml" namespace after install .Net package

Hello everyone,

I would like to use some function in “System.Security.Cryptography.Xml” .Net package, especially use System.Security.Cryptography.Xml.signedXml variable type. I have install System.Security.Cryptography.Xml in my dependencies but can not see it in Imported namespace. Is there some ways I can handle it?

Thank you!!