I am trying to add a SELECT ALL functionality to my grid with LINQ, but I get a compilation error.
List<Person_> PeopleUpdated = People.ToList().ForEach(a => a.SELECTED = true).ToList();
It says
Cannot implicitly convert type 'void' to 'System.Collections.Generic.List < LogoSapHrIntegration.frmXmlUpload.Person_>'
what am I doing wrong?
The List<T>.ForEach has no return value (ie void), so you can't run ToList() against that. (see MSDN)
ForEach a specific action for each item in the list (just like doing a real for loop).
In your case a simple for loop to select all is most efficient.
foreach (var person in People)
person.Selected = true
List<T>.ForEach returns void (in your case, it changes your collection in place). ForEach takes an Action<T> and executes that on each item of your list.
The ForEeach method (which is not LINQ) runs an action on each item in the list, it's not used to filter out items from a list so it doesn't return a result.
Just run the method on each item; there is no result to assign:
People.ToList().ForEach(a => a.SELECTED = true);
If you wanted a new list of items where the property was changed, you would need to clone the items to make them separate from the originals:
List<Person_> PeopleUpdated = People.ToList().Select(a => {
Person_ b = a.Clone();
b.SELECTED = true;
return b;
}).ToList();
(If the class doesn't support cloning, you would need to implement the Clone method (and preferably the IClonable interface).)
First of all, you can use a normal foreach loop:
foreach (var person in people)
{
person.Selected = true;
}
Which is the simplest and cleanest.
If you really want to jump to hoops and use LINQ, you can use ConvertAll:
var list = new List<Person> { new Person(), new Person() };
var convertedPeople = list.ConvertAll(person =>
{
person.Selected = true;
return person;
});
