Extension method method/parameterproblem
An error has occurred due to one of the following reasons:
- The specified extension method has no parameters. It must have at least one.
- The extension method you declared is non‑static. It must be static.
- You declared an extension method in a class that is either generic or non‑static (or both).
- The extension method’s first parameter type is a group or a non‑CLS structure.