{"id":372,"date":"2009-12-11T23:00:55","date_gmt":"2009-12-12T04:00:55","guid":{"rendered":"http:\/\/www.ikriv.com\/blog\/?p=372"},"modified":"2009-12-11T23:00:55","modified_gmt":"2009-12-12T04:00:55","slug":"public-classes-protected-methods-and-limitations-of-c-visibility-control","status":"publish","type":"post","link":"https:\/\/ikriv.com\/blog\/?p=372","title":{"rendered":"Public Classes, Protected Methods and Limitations of C# Visibility Control"},"content":{"rendered":"

I had an interesting problem today. I had a public class in my assembly called Session<\/code>. It was a public class, but it used a lot of internal stuff in the implementation. It went something like this:<\/p>\n

\n
public<\/span> class<\/span> Session<\/span>
\n{
\n    (public<\/span> methods and properties here)<\/p>\n

    private<\/span> void<\/span> HandleResponse(Response response) \/\/ Response class is internal<\/span>
\n    {
\n        …
\n    }
\n}<\/div>\n<\/div>\n

Later I needed to split it into two classes: MarketDataSession<\/code> and TradeSession<\/code>. They have a lot in common, but they need to handle responses slightly differently. I decided to keep shared functionality in Session<\/code> making it a base class. So, I modified Session like this:<\/p>\n

\n
public<\/span> class<\/span> Session<\/span>
\n{
\n    (public<\/span> methods and properties here)<\/p>\n

    protected<\/span> virtual<\/span> void<\/span> HandleResponse(Response response) \/\/ Response class is internal<\/span>
\n    {
\n        …
\n    }
\n}<\/p>\n

public<\/span> class<\/span> TradeSession<\/span> : Session …
\npublic<\/span> class<\/span> MarketDataSession<\/span> : Session …<\/div>\n<\/div>\n

I immediately ran into trouble: inconsistent accessibility, Response<\/code> class is less accessible then method HandleResponse<\/code>. Indeed, HandleResponse<\/code> is now a protected method of a public class, so theoretically it can be overriden outside of the assembly.<\/p>\n

I could make Session<\/code> an internal class, but public classes TradeSession<\/code> and MarketDataSession<\/code> are not allowed to derive from an internal class.<\/p>\n

The only solution that allows me to keep Response<\/code> class internal is to mark HandleResponse<\/code> method as internal. This makes it invisible from outside of the assembly, but now it is wide open inside the assembly, which is also not so stellar.<\/p>\n

There is another, rarely used access control option, protected internal<\/code>, but it actually means protected OR<\/b> internal, i.e. the method is accessible to anyone inside the assembly and to derived classes outside of the assembly.<\/p>\n

What I need here is protected AND<\/b> internal: accessible only to derived classes within the same assembly. AFAIK, this option exists in IL and in C++\/CLI as private protected<\/code> <\/a>. Here’s a real example where it would be useful in C#.<\/p>\n","protected":false},"excerpt":{"rendered":"

I had an interesting problem today. I had a public class in my assembly called Session. It was a public class, but it used a lot of internal stuff in […]<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"Layout":"","footnotes":""},"categories":[8],"tags":[],"class_list":["entry","author-ikriv","post-372","post","type-post","status-publish","format-standard","category-cs"],"_links":{"self":[{"href":"https:\/\/ikriv.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/372","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ikriv.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ikriv.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ikriv.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ikriv.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=372"}],"version-history":[{"count":0,"href":"https:\/\/ikriv.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/372\/revisions"}],"wp:attachment":[{"href":"https:\/\/ikriv.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=372"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ikriv.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=372"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ikriv.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=372"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}