I have the simplest VB code:
Dim test As String = "DDN8057"
You do not have Option Strict switched On in your VB project.
I can tell because
test.TrimStart("DDN") does not compile when this is on. This is because as you correctly pointed out
TrimStart expects an explicit char array (or a single char)
What happens when you run this with Option Strict Off is the compiler coerces the
DDN) into a single char (
D) (this is an implicit narrowing conversion which Option Strict expressly forbids) which is why you get
N8057 as your output.
You would think that as a string is just a char array it would convert it to an array but it doesn't - it effectively performs
Option Strict On = Good. Here is how to switch it on by default: Option Strict on by default in VB.NET