Code Inspection: Member can be made protected (non-private accessibility)
This is a solution-wide code inspection. It only works when the Solution-Wide Analysis is enabled.
ReSharper is smart enough to determine where a particular class member is actually being used. If it isn’t used outside the type or derived types, ReSharper will offer to mark the member as private. If the member is used in derived classes too, ReSharper will offer to mark it as protected.
Note that these recommendations need to be considered before being automatically applied. After all, you may be creating a public API, or you may be making types intended to be accessed in non-standard ways (for example, reflection). In this case, constraining visibility might not be a good idea. If necessary, you can always suppress the inspection.
For the solution-wide inspection to work, you need either or both of the following:
The simplified global usage checking is enabled — Show unused non-private type members when solution-wide analysis is off on the page of ReSharper options(Alt+R, O).
The solution-wide analysis is enabled — Enable solution-wide analysis on the page of ReSharper options(Alt+R, O).
Note that even if a symbol has no direct usages in your solution and ReSharper warns you about it, there could be cases where symbols are used indirectly — for example, via reflection — or they could just be designed as public API. In all those cases you would want to suppress the usage-checking inspection for the symbol, and there are several ways to do so:
The recommended way is to decorate the implicitly used symbols with code annotation attributes. There are two attributes for this purpose: [UsedImplicitly] and [PublicAPI], which are functionally similar, but let you and your teammates understand how the symbol is actually used.
You can also suppress usage-checking inspections with any custom attribute. To do so, mark the definition of that attribute with the [MeansImplicitUse] attribute.
And finally, you can suppress a specific usage-checking inspection as any other code inspection with a suppression comment or a suppression attribute.