.NET naming convention for “ID” (anything identification: Capitalization)

Question

I am in the process of unifying these inconsistent naming conventions and this one problem has been a bit driving me crazy lately.

In the code base I am working with has

Answer 1

Microsoft's naming guidelines suggest using all capitalized for 2 letter acronyms made into identifiers (IP, IO, UI, etc), so I tend towards "ID" (even though it's not an acronym) because when I read it, I still say the letters individually.

But honestly, I don't think Microsoft knows/knew what to do with ID/Id either:

ID

System.Runtime.InteropServices._Activator.GetIDsOfNames()
System._AppDomain.GetIDsOfNames()
System.Runtime.InteropServices._Attribute.GetIDsOfNames()
System.Type.GetTypeFromProgID()
System.Threading.Thread.ThreadID
System.Threading.Thread.GetDomainID()
System.Runtime.Serialization.ObjectHolder.ContainerID
System.Globalization.Calendar.ID
System.Globalization.CultureInfo.InvariantCultureID
System.Web.UI.Control.ClientID
System.Web.UI.Control.UniqueID

Id

System.AppDomain.GetCurrentThreadId()
System.AppDomain.GetIdForUnload()
System.AppDomain.IsDomainIdValid()
System.AppDomain.GetId()
System.Attribute.TypeId
System.TypeLoadException.ResourceId
System.Reflection.AssemblyAlgorithm.AssemblyAlgorithmAttribute.AlgorithmId
System.Runtime.Remoting.Lifetime.Lease.GetNextId()
System.Xml.Xpath.XPathNavigator.UniqueId
System.Data.OleDb.DBPropSet.PropertyId

(from http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/dcb8e08b-026a-4903-a413-7dbdda131a82/)

I guess that's why they invented intellisense...

In regards to pluralization: in my mind the s should always be lower-case.