c# Trying to reverse a list

c# list reverse
Tom Gullen picture Tom Gullen · Aug 8, 2011 · Viewed 89.5k times · Source 
public class CategoryNavItem
{
    public int ID { get; set; }
    public string Name { get; set; }
    public string Icon { get; set; }

    public CategoryNavItem(int CatID, string CatName, string CatIcon)
    {
        ID = CatID;
        Name = CatName;
        Icon = CatIcon;
    }
}

public static List<Lite.CategoryNavItem> getMenuNav(int CatID)
{
    List<Lite.CategoryNavItem> NavItems = new List<Lite.CategoryNavItem>();

    -- Snipped code --

    return NavItems.Reverse();
}

The reverse doesn't work:

Error 3 Cannot implicitly convert type 'void' to 'System.Collections.Generic.List<Lite.CategoryNavItem>'

Any ideas why this might be?

Answer

Marc Gravell picture Marc Gravell · Aug 8, 2011

Try:

NavItems.Reverse();
return NavItems;

List<T>.Reverse() is an in-place reverse; it doesn't return a new list.

This does contrast to LINQ, where Reverse() returns the reversed sequence, but when there is a suitable non-extension method it is always selected in preference to an extension method. Plus, in the LINQ case it would have to be:

return someSequence.Reverse().ToList();

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