Setting Spatial Reference for Geometry Bag using ArcObjects and VBA?

Question

Within the ESRI SDK resources there is an example of combining polygons by use of a geometry bag. The following code appears:

    'Define the spatial reference of the bag before adding geometries to it.
    geometryBag.SpatialReference = geoDataset.SpatialReference

That makes sense, based on some of the other documentation surrounding geometry bags, but when I tried it myself, I got a compile error saying that the method didn't exist. After looking at the geometry object model diagram, it appears as if the spatial reference property of a geometry bag is read-only... so what gives?

Answer 1

Cast the geometry bag to an IGeometry first, then try setting its SpatialReference property.

The behavior you describe is weird, though, since IGeometryBag descends directly from IGeometry. Are you sure you are trying to set the spatial reference on the correct interface?