how to check if IQueryable

My (EF db first) type sits behind interface IPolicyNumber. I get IQueryable<T> and want to check what I got is correct type (does this table is searchable by that column which is determined by having that interface). Currently I am using typeof(IPolicyNumber).IsAssignableFrom(typeof(T)) which is a bit old school, I was wondering if there was a way to use something like:

IQueryable<T>.ElementType is IPolicyNumber

Full method is below:

public static IQueryable<T> ApplySearch<T>(this IQueryable<T> queryable, SearchModel search) where T : class 
    {
        if (search != null && search.PolicyNumber.HasValue && typeof(IPolicyNumber).IsAssignableFrom(typeof(T)))
        {
           queryable = queryable.SearchByPolicyNumber(search);
        }

        return queryable;
    }

public static IQueryable<IPolicyNumber> SearchByPolicyNumber<IPolicyNumber>(this IQueryable<IPolicyNumber> queryable, SearchModel search)
    {
        var policyNumberParameterLambda = Expression.Parameter((typeof(IPolicyNumber)));
        var policyNumberColumnLambda = Expression.Property(policyNumberParameterLambda, "POLICY_NO");
        var lambda = Expression.Lambda<Func<IPolicyNumber, bool>>(
          Expression.Equal(policyNumberColumnLambda,
              Expression.Convert(Expression.Constant(search.PolicyNumber), policyNumberColumnLambda.Type)
          ), policyNumberParameterLambda);
        return queryable.Where(lambda);
    }