public AssociationDescription( 
   AssociationType type,
   RowHandle row1,
   RowHandle row2,
   double percentAlong
)

{
  // This routine creates a pole and a transformer bank, and then creates a structural attachment association between them, all in a single edit operation
  static void CreateUNFeaturesAndAssociations(FeatureLayer transformerBankLayer,
  Dictionary<string, object> transformerBankAttributes, FeatureLayer poleLayer,
  Dictionary<string, object> poleAttributes)
  {
    // Create an EditOperation
    EditOperation editOperation = new EditOperation();
    editOperation.Name = "Create pole; create transformer bank; attach transformer bank to pole";

    // Create the transformer bank
    RowToken transformerBankToken = editOperation.Create(transformerBankLayer, transformerBankAttributes);

    // Create a pole
    RowToken poleToken = editOperation.Create(poleLayer, poleAttributes);

    // Create a structural attachment association between the pole and the transformer bank
    RowHandle poleHandle = new RowHandle(poleToken);
    RowHandle transformerBankHandle = new RowHandle(transformerBankToken);

    AssociationDescription poleAttachment =
      new AssociationDescription(AssociationType.Attachment, poleHandle, transformerBankHandle);

    editOperation.Create(poleAttachment);

    // Execute the EditOperation
    editOperation.Execute();
  }
}