我不能在.ascx上使用IEnumerable（）吗？

Question

This is my code :

protected IEnumerable<MyObject> CategoriesHotelsFiltrati;
CategoriesHotelsFiltrati.Union(CategoriesHotels.Where(o => o.Comune != null && CategoriesLocalitaSelezionate.Contains(o.Comune.UniqueID)));

now, on .asxc, if I try to do :

<% 
    if (m_oHotelsFiltrati == null || m_oHotelsFiltrati.Count()==0)
    {
        Response.Write("hello");
    }
%>  

seems that it doesnt find .Count() method. It says somethings about "using" or "assembly". Strange, with IList<> this works perfectly...why?

Answer 1

You need to add the following line to your *.ascx file:

<%@ Import namespace="System.Linq" %>

See this link for more details.

Answer 2

.Count() is an extension method, it's not actually a method of IEnumerable . You need to have a using for System.Linq for the compiler to find the method. (As per comment by Anthony Pegram, you would use the import command for a markup file.)

It works fine with an IList because list actually has a property Count ; it doesn't rely on the extension method.

Answer 3

With IList<> you're probably calling the Count property (without parentheses). You can call Count() as a static method:

<%  
    if (m_oHotelsFiltrati == null || Enumerable.Count(m_oHotelsFiltrati)==0) 
    { 
        Response.Write("hello"); 
    } 
%>   

I'm not sure how to get extension method resolution in the .ascx file.