ArcGIS的 UID

关于什么是GUID，ProgID ，CLSID和UID，在ESRI的Document Library能够找到下面的描述.

COM interfaces and coclasses are identified by a globally unique identifier (GUID). The GUID for an interface is called an interface ID (IID). The GUID for a coclass is called class ID (CLSID). A ProgID is a text alias for a CLSID; the ProgID is a string
composed of the project name and the class name of the coclass.

The UID coclass can be used to represent the GUID of an object.

There is built-in module called ArcID in the VBA project for the Normal template in both ArcMap and ArcCatalog. This module is a utility for finding the UID of the built-in commands and toolbars. You pass the name of a command or toolbar in as an argument
to ArcID and the UID of that item is returned. The ArcID module is regenerated every time the Normal template is loaded; the registry is read to get the GUIDs of all the commands and toolbars that are currently used by the application.

简单的说，GUID(全局统一标识符)是用来标识识別COM接口和组件，保证它们的唯一性，避免出现版本不一致而导致的组件冲突.IID就是接口的GUID表示，CLSID则是组件类的GUID表示。ProgID是程序员给某个CLSID指定一个易记的名字.UID则是物象（Object)的GUID. 以下是一些ILayer接口的UID,通过使用它们，我们可以快速找到所需的图层。 这些ESRI接口存放在注冊表中的 HKEY_CLASSES_ROOT下面，如果想查询它们的UID，可以通过查找它们的名字，从而找到对应的UID.


{6CA416B1-E160-11D2-9F4E-00C04F6BC78E} IDataLayer


{40A9E885-5533-11d0-98BE-00805F7CED21} IFeatureLayer


{E156D7E5-22AF-11D3-9F99-00C04F6BC78E} IGeoFeatureLayer


{34B2EF81-F4AC-11D1-A245-080009B6F22B} IGraphicsLayer


{5CEAE408-4C0A-437F-9DB3-054D83919850} IFDOGraphicsLayer


{0C22A4C7-DAFD-11D2-9F46-00C04F6BC78E} ICoverageAnnotationLayer


{EDAD6644-1810-11D1-86AE-0000F8751720} IGroupLayer


{D02371C7-35F7-11D2-B1F2-00C04F8EDEFF} IRasterLayer

下面是一个查找groupLayer的例子




Public Function FindGroupLayer()Function FindGroupLayer(ByVal sGroupName_IN As String, ByRef pmap_IN As IMap) As ILayer


On Error GoTo errhandle




Dim Result As ILayer


Set Result = Nothing


Dim pL As IGroupLayer


Dim pel As IEnumLayer


Dim uid As New uid




uid.Value = "{EDAD6644-1810-11D1-86AE-0000F8751720}"




Set pel = pmap_IN.Layers(uid, True)




Set pL = pel.Next


Dim sGroupName As String


sGroupName = UCase(sGroupName_IN)




While Not pL Is Nothing




If UCase(pL.Name) = sGroupName Then


Set FindGroupLayer = pL


Exit Function


End If




Set pL = pel.Next


Wend


Set FindGroupLayer = Result




Exit Function




errhandle:


'MsgBox "FindgroupLayer Error: " & Err.Description


Set FindGroupLayer = Nothing


End Function