Lambda expression not working

Question

I am trying to clear all existing selections of a property but its not working with a lambda expression.

I have tried using "All" but it return a bool and does not work in this case. How can I accomplish this using lambda?

var permGroup = (ObservableCollection<PermissionGroup>)
 this.choicesOptionsTree.ItemsSource;
// NOT WORKING 
permGroup.All(pg => pg.Permissions.All); 
// WORKING 
//clear all existing selections).
foreach (var perGrp in permGroup)
{
 foreach (var perm in perGrp.Permissions)
 {
 perm.Selected = false;
 }
}

• leppie: What is pg.Permissions.All ?
• Jon Limjap: It looks like you're merely calling a property, and not a method call.
• Alex: @leppie Permissions seems to be another enumeration and All would be the LINQ-ALL

Answer 1

You can use:

foreach (var perm in permGroup.SelectMany(x => x.Permissions))
{
 perm.Selected = false;
}

• Mattias Josefsson: Dosent this just loop thru one permGroups Permissions?
• Simon Whitehead: This is the best answer by far because it doesn't make the assumption that the OP will know to cast to a List<T>.

Answer 2

All() is for determining if all elements in the collection satisfy a given condition, not for performing an action on all elements.

You want to use ForEach() -

permGroup.ForEach(pg => pg.Permissions.ForEach(perm => perm.Selected = false));

• Simon Whitehead: ObservableCollection doesn't have a ForEach method.. List<T> does.
• Simon Whitehead: You realise he's casting permGroup to an ObservableCollection<T> yes?
• Dryadwoods: Yes, I saw it, but the question is, can he change it? or does he really needs to use it in that way?
• Simon Whitehead: ..perhaps consider casting it to a List and explaining that then? As it stands, your example will not compile.

Answer 3

permGroup.ForEach(pg => pg.Permissions.ForEach(p => p.Selected = false)); 

• Leri: Why are you sure that pg.Permissions is enumerable?
• Matías Fidemraizer: @PLB If it's not enumerable you wouldn't be able to use foreach too :/
• Leri: @MatíasFidemraizer I have not read complete code. My fault. I thought All was a property of type of pg.Permissions. :)

Answer 4

Here is another couple of ways

permGroup.SelectMany(pg => pg.Permissions).ForEach(x => x.Selected = false);

or

foreach (var permission in groups.SelectMany(x => x.Permissions))
 permission.Selected = false;