А где spatial reference, хотя бы unknown? В ArcObjects Developer Help есть пример "Create a new geodatabase dataset":
Public Function createDataset(Name As String, workspace As esriCore.IWorkspace, _
Optional pSR As esriCore.ISpatialReference) As esriCore.IFeatureDataset
'' createDataset: creates a dataset in a workspace
'' ISpatialReference is optional but should generally be defined by the caller
''
Dim pFeatureWorkspace As esriCore.IFeatureWorkspace
On Error GoTo EH
Set createDataset = Nothing
If workspace Is Nothing Then Exit Function
' if the spatial reference is not passed in, then create an unknown one here
If (pSR Is Nothing) Or IsMissing(pSR) Then
Set pSR = New esriCore.UnknownCoordinateSystem
pSR.SetDomain 0, 21474.83645, 0, 21474.83645
pSR.SetFalseOriginAndUnits 0, 0, 100000
pSR.SetMDomain 0, 21474.83645
pSR.SetZDomain 0, 21474.83645
pSR.SetZFalseOriginAndUnits 0, 100000
End If
Set pFeatureWorkspace = workspace
' create the feature dataset
Set createDataset = pFeatureWorkspace.CreateFeatureDataset(Name, pSR)
Exit Function
EH:
MsgBox Err.Description, vbInformation, "createDataset"
End Function