GetViewByMorefs causes "Required parameter specSet is missing" for HostSystem

Hello,

I am attempting to get a collection of HostSystem objects in a specific cluster using the VMware.Vim API that comes with PowerCLI 6. I can retrieve the cluster by doing:

var clusters = client.FindEntityViews(typeof(ClusterComputeResource), null, null, null).Cast<ClusterComputeResource>();

For each of these clusters, I can inspect the Host property to get an array of MoRef's that point to each host in the cluster. However, when attempting to retrieve the hosts using:

var hosts = client.GetViewsByMorefs(cluster.Host, "Name", "Summary", "Vm").Cast<HostSystem>();

An exception is thrown:

Required parameter specSet is missing


while parsing call information for method RetrieveProperties

at line 1, column 218


while parsing SOAP body

at line 1, column 207


while parsing SOAP envelope

at line 1, column 38

I have tried both with and without specifiying the params string[] properties parameter specified, but I get the same result either way. Is there something I'm missing?

I have also tried past versions of the library (5.5 and 5.0), and encounter the same problem.

Thanks!