C# object is not null but (myObject != null) still return false

Question

I need to do a comparaison between an object and NULL. When the object is not NULL I fill it with some data.

Here is the code :

 if (region != null)
         


        

Answer 1

Both of the overloads are incorrect

 public static bool operator ==(Region r1, Region r2)
    {
        if (object.ReferenceEquals(r1, null))
        {
            return false;
        }
        if (object.ReferenceEquals(r2, null))
        {
            return false;
        }

        return (r1.Cmr.CompareTo(r2.Cmr) == 0 && r1.Id == r2.Id);
    }

if r1 And r2 are null, the first test (object.ReferenceEquals(r1, null)) will return false, even though r2 is also null.

try

//ifs expanded a bit for readability
 public static bool operator ==(Region r1, Region r2)
    {
        if( (object)r1 == null && (object)r2 == null)
        {
           return true;
        }
        if( (object)r1 == null || (object)r2 == null)
        {
           return false;
        }        
        //btw - a quick shortcut here is also object.ReferenceEquals(r1, r2)

        return (r1.Cmr.CompareTo(r2.Cmr) == 0 && r1.Id == r2.Id);
    }

Answer 2

This can sometimes happen when you have multiple threads working with the same data. If this is the case, you can use a lock to prevent them from messing with eachother.