SysObsoleteAttribute X++ Language Reference

What is an attribute class in xpp? An attribute class in X++ can either directly extend the SysAttribute class or any of its descendants. You should not use it directly because it is an abstract class, as these can’t be used without inheriting the class.

SysObsoleteAttribute
X++ SysObsoleteAttribute is something also covered among other basics in our xpp developer guide mar 2025 for designating methods, variables or even classes as no longer really valid for use. It is to tell the compiler to fail in case that some obsolete method is being used in your codebase.

Some overview X++ SysObsoleteAttribute training info can be as follows:

Suppose an example

[SysObsoleteAttribute("The NewCar class might be faster.", false)]
class ClassicTruck
{
// Members of ClassicTruck class go right here.
}

So what is the purpose of the second parameter of SysObsoleteAttribute and what does true or false do? Or, how can you tell SysObsoleteAttribute to generate a compile time error or instead just give a compile time warning but allow your X++ to compile anyway?

The 2nd parameter false is known as _isError in Dynamics 365 FinOps X++ SysObsoleteAttribute and is similar to ObsoleteAttribute in .NET. The purpose of the _isError argument of the SysObsoleteAttribute decorator is to tell the compiler whether it should generate a compile time error (true) or warning (false) on any actual usage of the decorated class, method or whatever scope in X++ code and that is how you use this attribute and argument.