I saw this in saample source code project.
[Input]
public int Length { get; set; }
It was defined in a class:
namespace PowerLanguage.Strategy
{
public class MovAvg_Cross_SE : SignalObject
{
....
What does the [input] mean?
That’s an Attribute — a way to declare information about your source code. What your particular attribute means depends on the namespace of the attribute. You can hover over it to get information on it or (if the declaration is part of your project) ctrl-click on it to see its source.