Lambda表达式和方法调用

Question

Hi I have a collection of Objects in a Listview and i need to know if i can iterate through them with a lambda expression. and call a method on it in the expression.

Lets say i need to save a group of people to a database.

List<People> someList;
someList.Select(person => person.Save());

is this possible to do? so far i have not been able to get it working. thanks

Answer 1

You can use the ForEach method of a generic list:

List<People> someList;
someList.ForEach(person => person.Save());

Answer 2

someList.ForEach(p => p.Save());

Answer 3

Sounds like you want a foreach statement:

foreach(People p in someList)
{
    p.Save();
}

But if you really want to do it in lambda expressions and LINQ, then your problem with the above code is that .Select(...) returns an IEnumerable/IQueryable, which creates a new query but doesn't execute your lambda expressions.

You could force the lambda to evaluate by calling an extension method that forces an enumeration of the data the IEnumerable/IQueryable represents. For instance by doing:

someList.Select(person => person.Save()).Count();

but this also assumes your Save() method returns non-void.

Edit: As others have pointed out, if you're working specifically with a List<>, then you can also do:

someList.ForEach(person => person.Save());