\nI answered a question on the newsgroups on how *exactly* inheritence works when you use it implement UDTs in SQL Server 2005. Also wanted to record the explanation here….\n<\/p>\n
\nIt doesn't work like you'd expect inheritence to when to use T-SQL, because SQL Server is blissfully unaware of the inheritence relationships (they're not recorded in the system views).\n<\/p>\n
\nSo if the class Tiger inherits from the class Cat. Passing an instance of Tiger to the T-SQL stored procedure FeedTheCat:
\ncreate procedure FeedTheCat (@thecat Cat) …. — T-SQL here —
\nwouldn't work.\n<\/p>\n
\n— (Msg 206: operand type clash dbo.Tiger is incompatible with dbo.Cat)
\ndeclare @t tiger
\nexecute feedthecat @t\n<\/p>\n
\n— or this (Msg 529: explicit conversion … is not allowed)
\ndeclare @c cat
\nset @c = cast(@t as cat)
\nexecute feedthecat @c\n<\/p>\n
\nIf the Cat class has a public instance method called FeedMe and a public field called pawcount (both are inherited by Tiger), this wouldn't work in T-SQL:\n<\/p>\n
\n— this wouldn't work
\ndeclare @t Tiger
\nprint @t.FeedMe()
\nprint @t.pawcount\n<\/p>\n
\n— this would
\ndeclare @c Cat
\nprint @c.FeedMe()
\nprint @c.pawcount\n<\/p>\n
\nYou could, however, access these fields\/methods on Tiger from .NET code, As in:
\n\/\/ works fine
\nTiger t = new Tiger();
\nint paws = t.pawcount;
\n\/\/ so does this
\nSqlString s = t.FeedMe();\n<\/p>\n
\nCalling it in .NET code *through SqlCommand.ExecuteReader* (CommandText = "select sometiger.pawcount from zootab") wouldn't work.<\/p>\n","protected":false},"excerpt":{"rendered":"
I answered a question on the newsgroups on how *exactly* inheritence works when you use it implement UDTs in SQL Server 2005. Also wanted to record the explanation here…. It doesn't work like you'd expect inheritence to when to use T-SQL, because SQL Server is blissfully unaware of the inheritence relationships (they're not recorded in […]<\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[28,38],"tags":[],"class_list":["post-985","post","type-post","status-publish","format-standard","hentry","category-sql-server-2005","category-sqlclr"],"yoast_head":"\n