Using Extensions: Weighing The Pros vs Cons

Question

Recently I asked a question about how to clean up what I considered ugly code. One recommendation was to create an Extension Method that would perform the desired function

Answer 1

The only serious weirdness to deal with in Extension methods are:

1. They do not have to cause a null reference exception if the left hand side (the object on which it appears you are invoking a method) is null.
   • can sometimes be useful, but is contrary to expectations as such should be used with extreme caution.
2. They are not accessible through reflection on the classes/interfaces to which they apply.
   • generally not a problem, but worth keeping in mind.
3. Name collisions with other extension methods involve a lengthy resolution rule sequence
   • if you care the sequence is to prefer:
     1. Extension methods defined inside the current module.
     2. Extension methods defined inside data types in the current namespace or any one of its parents, with child namespaces having higher precedence than parent namespaces.
     3. Extension methods defined inside any type imports in the current file.
     4. Extension methods defined inside any namespace imports in the current file.
     5. Extension methods defined inside any project-level type imports.
     6. Extension methods defined inside any project-level namespace imports.