C# Use discard '_'

Question

I'm not quite sure of the different between

DataTable itemTable = new DataTable();
itemTable = //CODE

and

_ = new DataTable();
DataTable itemTable = //CODE

Both worked exactly the same, why would I need to change it to an _ like shown?

IMAGE OF THE "POTENTIAL FIX"

Answer 1

Because you have not used the value new DataTable() after assigning, the intellisense thought that you won't need it, so just made the leftside wildcard.

Its just like:

int a = 5;
a = 6; // you didn't even used the value 5 assigned above!

But, in case that the constructor of DataTable has side-effect, the intellisense suggested you not to discard the entire statement, using wildcard _. That's what happened.

If the constructor of DataTable has no side-effect, you are free to remove the statement, just like the above int example.