CODEWITHSUNDEEP
c#.netlinqc#-4.0
4thSpace
4thSpace

Reputation: 44342

Calling method with linq syntax based on condition

How do I loop through a generic list and call a method based on a couple of conditions? I'd like to use linq syntax. The following doesn't work of course. Any ideas?

somelist.ForEach(i => i.DeptType == 1 && i != null () {MyMethod(someInt)});

If that isn't possible, what is the next best method using concise syntax?

Upvotes: 2

Views: 3199

Answers (5)

Amy B
Amy B

Reputation: 110131

//standard style ... since Linq is Functional/side-effects-free
foreach(var x in somelist.Where(i => i != null && i.DeptType == 1))
{
  SomeMethod(x);
}

//anon method style ... for those that must use ForEach
somelist.ForEach(i => {if (i != null && i.DeptType == 1) {MyMethod(someInt);}});

Upvotes: 4

Jim Patterson
Jim Patterson

Reputation: 307

I'd use:

    somelist.Where(q => q !=null)
    .Where(q => q.DeptType == 1)
    .Select(q => MyMethod(q));

The resulting collection will contain a list of return values for the original values/method calls that were acted upon.

Upvotes: 0

Jon Senchyna
Jon Senchyna

Reputation: 1

One thing to keep in mind, you should make sure you do your null-checks before you access your object's fields, as in the following:

somelist.Where(i => i != null && i.DeptType == 1).ToList().ForEach( i=> MyMethod(i.someInt));

As someone above pointed out, you cannot call ForEach() on the Generic IEnumerable object returned from the Where() call. You must first call ToList() to save the results to a Generic List. I have updated the code above to include that change.

Upvotes: 0

Douglas
Douglas

Reputation: 54887

As appealing as one-liner LINQ queries may be, they’re typically associated with operations that do not have any side-effects (e.g. query projection, filtering, etc). In your case, you might be better served with a traditional foreach loop:

foreach (var i in somelist)
    if (i != null && i.DeptType == 1)
        MyMethod(someInt);

P.S. Your original condition, i.DeptType == 1 && i != null, is ordered incorrectly. The code will still give rise to a NullReferenceException since i.DeptType is executed before i is null-checked.

Upvotes: 2

Abe Miessler
Abe Miessler

Reputation: 85056

Try using Where to specify which records you want to select and ForEach to execute your method:

somelist.Where(i => i.DeptType == 1 && i != null)
           .ToList()
           .ForEach( i=> MyMethod(i.someInt));

Upvotes: 6

Related Questions