update multiple elements at once LINQ

Question

Is it possible to set property on each element from List using LINQ.

for example:

var users = from u in context.Users where u.Name == \"George\" sele         


        

Answer 1

How about:

 context.Users.Where(u => u.Name == "George").Select(u => u.MyProp = false);

Answer 2

You can create your own ForEach extension method:

public static IEnumerable<T> ForEach<T>(this IEnumerable<T> source, Action<T> action)
{
    foreach (var element in source)
    {
        action(element);
    }

    return source;
}

Then your code can be simplified to:

context.Users.Where(x => x.Name == "George").ForEach(u => u.MyProp = false);

EDIT: You could also yield return each item after the call to action() (no pun intended) to leave the deferred execution untouched.

Answer 3

Looks dirty but if asked (just via select), I'll do it this way

var users = from u in context.Users where u.Name == "George" 
select new User() 
{
   prop1 = u.prop1,
   prop2 = u.prop2,
   prop3 = true // update like here
};

if you wish to use some other C# function, you can also use linq functions and work on IEnumerable type of lists.

var users = context.Users.Where(u => u.Name == "George").ToList()
    .Select(p => new User() 
    {
       prop1 = p.prop1,
       prop2 = p.prop2,
       prop3 = ComputeHash(p) // update like here
    });

Code above becomes IEnumerable because of the .ToList() prior to the .Select()

Answer 4

What is cleaner is quite subjective. Personally, I find this approach hard to beat for clarity and simplicity:

foreach (User us in users.Where(u => u.Name == "George"))
{
   us.MyProp = false;
}

Answer 5

Or you can convert it to ToList() and use ForEach method.

users.ToList().ForEach(u => u.MyProp = false);

to update more than one properties

users.ToList().ForEach(u =>
                      {
                         u.property1 = value1;
                         u.property2 = value2;
                      });

Or like this

(from u in context.Users where u.Name == "George" select u).ToList()
.ForEach(u => u.MyProp = false);

Answer 6

If you're interested in in-memory update, that is the database is not going to be updated then you could use

var users = (from u in context.Users where u.Name == "George" select u).ToList();
users.ForEach(u => u.MyProp = "Something");