null == null返回false？

Question

Can anyone provide any ideas why my null check is evaluating incorrectly?

It should also be pointed out, that if i is not null, the evaluation is correct. I'm not sure what else is relevant, but let me know what other details I need to provide.

foreach (var item in selectedItems)
{
    var i = inspectionItems.Keys.SingleOrDefault(x => x.InspectionItemId == item.InspectionItemId);
    if (i != null)
    {
        // Process i
     }
     else
     {
       // create
     }
}

Answer 1

My guess would be that you overloaded the == operator. The result of Object.Equals(i, null) could confirm that.

If you are overloading the == operator, it's possible your logic is incorrectly handling the null case.

Answer 2

One [devious] way to get this to happen would be :-

    public enum Cheat
    {
        @null = 0,
        foo = 1,
        bar = 2
    }

If you assign Cheat.@null to i you get the watch values you show.

What is the type of i ? Either it displays in the debugger as null or you've done something else in that class that could cause == to fail.