How to avoid null checking before foreach IList

Question

I have the following code:

IList<object> testList = null;

... 

if (testList != null) // <- how to get rid of this check?
{
   foreach (var item in testList)
   {
       //Do stuff.
   }
}

Is there a way to avoid the if before the foreach? I saw a few solutions but when using List, is there any solution when using IList?

why do you care? If there's a possibility it might be null, then you need to check. Not a big deal really. As Dmitry shows, you can cheat by initialising as an empty list of objects, which means it won't loop, but to me it seems pointless to initialise something in memory just to save a line of code — ADyson, Nov 20 '19 at 11:00
fubo yes, my mistake. DmitryBychenko I think this will work, thanks! — Milen Grigorov, Nov 20 '19 at 11:01

score 10 · Accepted Answer · answered Nov 20 '19 at 11:01

Well, you can try ?? operator:

testList ?? Enumerable.Empty<object>()

we get either testList itself or an empty IEnumerable<object>:

IList<object> testList = null;

...

// Or ?? new object[0] - whatever empty collection implementing IEnumerable<object>
foreach (var item in testList ?? Enumerable.Empty<object>())
{
    //Do stuff.
}

score 6 · Answer 2 · answered Nov 20 '19 at 11:00

6

Try this

IList<object> items = null;
items?.ForEach(item =>
{
  // ...
});

answered Nov 20 '19 at 11:00

Ashu

467
1
7
19

score 2 · Answer 3 · answered Nov 20 '19 at 11:08

2

I stole the following extension method from a Project:

public static IEnumerable<T> NotNull<T>(this IEnumerable<T> list)
{
    return list ?? Enumerable.Empty<T>();
}

Then use conveniently like this

foreach (var item in myList.NotNull())
{

}

answered Nov 20 '19 at 11:08

Charles

2,721
1
9
15

score 1 · Answer 4 · answered Nov 20 '19 at 11:10

1

you can create extention method like this :

public static IList<T> OrEmptyIfNull<T>(this IList<T> source)
 {
       return source ?? Enumerable.Empty<T>().ToList();
 }

Then you can write:

 foreach (var item in testList.OrEmptyIfNull())
    {
    }

answered Nov 20 '19 at 11:10

Milad kamari

11
1

How to avoid null checking before foreach IList

4 Answers4