Feature editing fails in an editable layer

Description

When editing layers, features from an editable layer are not editable.

Cause

When using query filter, only a subset of fields contained in the feature layer is returned. For example:

Code:

using (FeatureDataReader reader = featureLayer.GetDataReader(new QueryFilter(new Envelope(e.MapCoordinate,
map1.ToMap(3),map1.ToMap(3)), EsriGeometricRelationship.Intersect),"tempfield", featureLayer.GeometryColumnName))
 {
   if (reader.Read())
     {        
      reader.SetInt32(reader.GetOrdinal("tempfield"), 1); //  throws an exception
      reader.Update();
     }
  }

Solution or Workaround

Code:

using (FeatureDataReader reader = featureLayer.GetDataReader(new QueryFilter(new Envelope(e.MapCoordinate,
map1.ToMap(3),map1.ToMap(3)), EsriGeometricRelationship.Intersect)))
 {
   if (reader.Read())
     {        
      reader.SetInt32(reader.GetOrdinal("tempfield"), 1);
      reader.Update();
     }
  }