Microsoft.identitymodel.claims.claimsidentitycollection doesnot contain a definition for "first"

Question

I am getting the problem mentioned in subject :  Microsoft.identitymodel.claims.claimsidentitycollection doesnot contain a definition for "first"and no extension method "First" accepting an argument  of type Microsoft.identitymodel.claims.claimsidentitycollection could be found

Here is my line in my code which is throwing error:

var identity = handlers.validatetoken(token).first();