I think of one the most mystifying error messages that you can get in SQL Server 2005 is when try to catalog the same assembly twice into the same database:
Msg 6285, Level 16, State 1, Line 1
CREATE ASSEMBLY failed because the source assembly is, according to MVID, identical to an assembly that is already registered under the name "...".
This raises a couple of interesting questions.
a.) What the heck is an MVID and why do we care?
b.) How can we check these MVIDs for ourselves?
a.) MVID stands for Module Version ID and is documented in section 21.27 of ECMA-335 as "simply a Guid used to distinguish between two versions of the same module." Although an Assembly can contain many modules, there is a principal MVID assigned to it in the manifest -- the Manifest MVID. One of the checks that SQL Server performs when cataloging an new assembly is to get it's Manifest MVID and compare that to all of the other Manifest MVIDs for assemblies already cataloged in the current database. When a duplicate is found, SQL Server 2005 rejects the inbound assembly.
b.) Checking any non-database assembly for its Manifest MVID is fairly simple. Here's a short snip of code that returns it:
Assembly asm = Assembly.Load(BUF);
Module m = asm.ManifestModule;
return m.ModuleVersionId;
Where BUF is assumed by an array of bytes holding the assembly you want the MVID for. You could also use Assembly.LoadFromFile to an exsiting Assembly-as-DLL file into the snip, however, that method is not allowed within SQLCLR. An easier way to get the MVID for an Assembly already cataloged into SQL Server 2005 is to use the AssemblyProperty statement in T-SQL, e.g.:
select assemblyproperty(assembly name,'mvid')
A few weeks back, the ADO.NET team released the first in a series of ADO.NET v.Next releases. This was our first look at several exciting technologies like the Entity Data Framework and Mapping Views. Well today, the team announced the release a designer for working with ADO.NET v.Next Entity data.
Go have a look-see.
I'm teaching a class in Montréal this week and, honestly, this is quickly becoming one of my favorite cities. Many thing have stood out for me, but the most noticable thing for me is just how quiet this city is. The roar of the traffic, the scream of sirens and the general din of having thousands of people concurrently on the streets just isn't here. And, while I don't speak much French at all, I've had almost no problem getting along and getting business done.
Of couse, there are some other notable differences. The no ice skating signs. Nearly filling a stadium for a PRE-session hockey game. Sushi Bars on every other block. Decent Beer. Yeah, like any of those things are a problem for me.
Yes, its a little price and sure, its gets a bit colder at night than I'm used to. But I find myself saying. Montréal -- Son gentil!