c# - Why is IQueryable lacking all the extension methods that IQueryable<T> has? -

same ienumerable vs ienumerable<t>. oversight? or there problem when don't have type specified makes implementing extensions .count(), .where(), etc impossible?

from docs:

the iqueryable interface intended implementation query providers. supposed implemented providers also implement iqueryable<t>. if provider not implement iqueryable<t>, standard query operators cannot used on provider's data source.

ienumerable artifact of times when .net did not have generics ( don't mean deprecated, of course ). has lived on backward compatibility, after generics , hence ienumerable<t> introduced. iqueryable keeps consistency. basically, given there generics now, , given advantages, makes useful implement these extensions on generic interfaces. non-generic ones can converted generic ones using cast<t>