CODEWITHSUNDEEP
c#.netlistunion
JGC
JGC

Reputation: 12997

Make some List Union in C#

I have 3 lists which every one of them has some instance of following class:

public class Menu
{
   public string Address { get; set; }
   public string Name { get; set; }
   public List<Menu> Childs=new List<Menu>();
}

I fill everyone of these list in code below:

public List<Menu> GetAvailableMenus(string[] roles)
{
    var adminMenu = new List<Menu>();
    var terminalMenu = new List<Menu>();
    var gaurdMenu = new List<Menu>();
    if(roles.Contains("admin"))
    {
        GetAdminMenus(adminMenu);
    }
    if (roles.Contains("terminal"))
    {
        GetTerminalMenus(terminalMenu);
    }
    if (roles.Contains("gaurd"))
    {
        GetGaurdMenus(gaurdMenu);
    }                       
    return adminMenu.Union(gaurdMenu).Union(terminalMenu).ToList();
}

my problem is Union action just concat these list and do nor merge them in order to remove redundant items. does anyone has any idea what should I do?

Upvotes: 0

Views: 354

Answers (3)

dlev
dlev

Reputation: 48596

You haven't overridden Equals or GetHashCode for your Menu class, so Union has no way (except reference equality, which won't work here) to know that there are duplicates. Implementing those methods in a sensible way will make your code work.

These links might help:

Alternatively, you can just pass in your own implementation of IEqualityComparer as another argument to the Union method.

Upvotes: 3

Stuart
Stuart

Reputation: 66882

If you provide an equality comparer for Union then it will be able to merge and not just concat your lists

See http://msdn.microsoft.com/en-us/library/bb358407.aspx

Update - reading your question again I'm wondering if you also want the child menu items merged too. If that's the case, then I think you will need to write some logic to do this - I don't think there's any way of using the Linq Union operator to do this nested merging.

Upvotes: 0

Lucero
Lucero

Reputation: 60190

Your Menu class needs to properly implement IEquatable<> in order to determine whether two entries are the same or not. Otherwise Union will use the default equality, which will compare reference equality.

Upvotes: 0

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