Рабочий вариант
private void OnActiveViewEventsSelectionChanged()
{
ICompositeLayer layer1;
IFeatureLayer layer;
layer1 = axMapControl1.get_Layer(2) as ESRI.ArcGIS.Carto.ICompositeLayer;
layer = layer1.get_Layer(0) as ESRI.ArcGIS.Carto.IFeatureLayer;
IBasicMap map = null;
ILayer layer2 = null;
layer.Selectable = true;
Object other = null;
Object index = null;
esriTOCControlItem item = esriTOCControlItem.esriTOCControlItemNone;
axTOCControl1.GetSelectedItem(ref item, ref map, ref layer2, ref other, ref index);
IGeoFeatureLayer player;
player = layer2 as IGeoFeatureLayer;
player.Selectable = true;
ESRI.ArcGIS.Geodatabase.IFeatureClass pFc;// = player as ESRI.ArcGIS.Geodatabase.IFeatureClass;
string strOIDName;
pFc = player.FeatureClass;
if(pFc!=null)
strOIDName = pFc.OIDFieldName;
ESRI.ArcGIS.Carto.IFeatureSelection pFSel;
pFSel = player as ESRI.ArcGIS.Carto.IFeatureSelection;
ESRI.ArcGIS.Geodatabase.ISelectionSet pSelSet;
pSelSet = pFSel.SelectionSet;
ESRI.ArcGIS.Geodatabase.ICursor pFCur;
pSelSet.Search(null, false, out pFCur);
int nlay = pFCur.FindField("Centr_lesn");
string centr = pFCur.NextRow().get_Value(nlay).ToString();
this.label2.Text = centr;
IFeatureSelection featureSelection = layer2 as IFeatureSelection;
ESRI.ArcGIS.Geodatabase.ISelectionSet selectionSet = featureSelection.SelectionSet;
}