How to check if a dynamic object is null

Question

I recently saw the following code, which puzzled me.

dynamic resultObj = SomeClass.run(arg);
if (resultObj == null || resultObj.ToString() == null)
{
    /* Error handling */
}

Assuming SomeClass is your typical class (which does not override ToString()), is there a reason why the second part of the conditional would be necessary? Also, are there other potential issues with this code as it is?

Answer 1

A dynamic can be checked for null directly, but some circumstances can cause false answers. In order to check a dynamic for null, you should cast it as an object. For example,

dynamic post = SomeMethod();
if (post.modified == null){
//could return errors.
}

in order to check this property for null, you should do something like this:

string.IsNullOrEmpty(Convert.ToString(post.Modified));

similarly, to check a dynamic for null, you should do something like this:

if ((object)post != null)

References:

https://ericlippert.com/2018/11/19/a-dynamic-definite-assignment-puzzle-part-2/

https://forums.asp.net/t/1592751.aspx?How+to+check+for+null+empty+strings+on+dynamic+objects+

So, by checking a resultObj.ToString() == null I believe this may convert the dynamic to an object and therefore enable for true null checking.