Custom DSC Resource Schema

Windows Powershell Desired State Configuration (DSC) allows you to build custom resources to implement new functionality. When creating my first custom resource I stumbled across a few gotchas in the TechNet documentation. After using the TechNet example MOF Schema I hit a few errors. My assumption is this is due to changes from the preview version to the actual release version.

TechNet Example Schema

[version("1.0.0"), FriendlyName("Website")] 
class Demo_IISWebsite : MSFT_BaseResourceConfiguration
{
  [Key] string Name;
  [write] string PhysicalPath;
  [write,ValueMap{"Present", "Absent"},Values{"Present", "Absent"}] string Ensure;
  [write,ValueMap{"Started","Stopped"},Values{"Started", "Stopped"}] string State;
  [write,ValueMap{"http", "https"},Values{"http", "https"}] string Protocol[];
  [write] string BindingInfo[];
  [write] string ApplicationPool;
  [read] string ID;
};

The first error occurred when generating the MOF files.

Fix: I opened the schema files that were installed, they inherited from “OMI_BaseResource” not “MSFT_BaseResourceConfiguration”

The second error was rather cryptic when trying to apply the MOF to the machine. ClassVersion Qualifier not found.

Fix: As with the first error, the documentation refers to a class attribute called “Version“, but it should be “ClassVersion” instead.

Working Schema

[ClassVersion("1.0.0"), FriendlyName("Website")] 
class Demo_IISWebsite : OMI_BaseResource
{
  [Key] string Name;
  [write] string PhysicalPath;
  [write,ValueMap{"Present", "Absent"},Values{"Present", "Absent"}] string Ensure;
  [write,ValueMap{"Started","Stopped"},Values{"Started", "Stopped"}] string State;
  [write,ValueMap{"http", "https"},Values{"http", "https"}] string Protocol[];
  [write] string BindingInfo[];
  [write] string ApplicationPool;
  [read] string ID;
};