what is [] brackets in .net?

You're seeing .Net attributes (VB or C#), which can annotate types and members.

They are used to put Attributes on classes or methods (or other stuff). That way, you can attach data to classes that should not be part of the actual class. You can read more on them here

They're attributes used to annotate methods and classes.

[] brackets are an operator in C#. The link contains more detailed information and examples of what I summarized below.

They are used for:

• Array type definition
• Access an element of an array
• They can be used as indexer parameters for any type
• They can be used to specify attributes <-- This seems like what you are asking about
• They can be used for unsafe code to index an offset from a pointer