c# - IGenericRepository<T> - Cannot resolve symbol where -

i'm following tutorial on unit of work pattern , code won't compile because doesn't recognise in interface signature , doesn't recognise type t.

using system; using system.collections.generic; using system.linq; using system.linq.expressions; using system.text; using system.threading.tasks;  namespace datalayer.repository {    public interface igenericrepository<t> : t : class {     iqueryable<t> asqueryable();      ienumerable<t> getall();     ienumerable<t> find(expression<func<t, bool>> predicate);     t single(expression<func<t, bool>>  predicate);     t singleordefault(expression<func<t, bool>> predicate);     t first(expression<func<t, bool>> predicate);     t getbyid(int id);      void add(t entity);     void delete(t entity);     void attach(t entity); } } 

can see i'm missing?

please remove :, this:

public interface igenericrepository<t> t : class