c# Extension methods - design patterns

Question

I would like to know if C# extension method is based on any existing design pattern.

Answer 1

They are not based on an existing design pattern. When this 'feature' was first introduced in Delphi, under the name 'class helpers', Borland even warned users away from them. They were considered a bit of a hack, but now the dust has settled they have found a place of their own.

Like everything else, use when appropriate.