Collapsing layers in ArcMap Table of Contents using ArcObjects?

Question

I'm stuck on how to collapse all layers in my ArcMap projects (9.3). I've tried a few bits of sample code, but they all seem to fail for some reason or other.

Some of the layers might be grouped, and some are imagery or WMS layers if that makes a difference.

Here is some code I have tinkered with, but does not work:

Dim pMxdoc As IMxDocument
Set pMxdoc = ThisDocument
Dim pFeatLayer As IFeatureLayer
Dim pEditLayers As IEditLayers
Set pEditLayers = pEditor
Dim pMap As IMap
Set pMap = pMxdoc.FocusMap
Dim pLayer As ILayer

'Collapse any expanded grouplayers
Dim pGroupLayer As IGroupLayer
For i = 0 To pMxdoc.FocusMap.LayerCount - 1
Set pLayer = pMxdoc.FocusMap.Layer(i)
'Check if the reached layer is a group
If TypeOf pLayer Is IGroupLayer Then
    Set pGroupLayer = pLayer
    if pGroupLayer.Expanded = true Then
        pGroupLayer.Expanded = false
    End if
End If
Next i
pMxdoc.UpdateContents
pMxdoc.ActiveView.Refresh

Answer 1

Try pGroupLayer.Expanded = false to collapse the group. As far as non-grouped layers, here is a snippet I used to collapse the legends on rasters in the TOC, it uses the ILegendGroup interface:

// Collapse the legends on each raster
ILegendInfo legendInfo = (ILegendInfo)pRasterLayer.Renderer;
ILegendGroup legendGroup = (ILegendGroup)legendInfo.get_LegendGroup(0);
legendGroup.Visible = false;

Answer 2

Extending on Chad's answer, following does the trick for feature layer with multiple legend groups

for (int k = 0; k <= (featureLayer as ILegendInfo).LegendGroupCount - 1; k++)
{
   (featureLayer as ILegendInfo).get_LegendGroup(k).Visible = false;
}

Answer 3

When the layer is an IAnnotationLayer, use the ICompositeLayer2 interface:

ICompositeLayer2 compositeLayer = (ICompositeLayer2)featureLayer;
compositeLayer.Expanded = false;

Answer 4

If you want to expand or collapse all layers, select the layers and either hit the subtract key or the plus key on the keyboard. Also, if you want to check or uncheck them, hit the spacebar on the selected layers.