Contract.cs

public class Contract{

public void AddAsset(decimal assetValue, int assetType) 
 { 
  Asset a = CreateAsset(assetValue, assetType);
  AddAssetToCollection(a);
  Save();
 }
 
 private Asset CreateAsset(decimal assetValue, int assetType)
 {
   return new Asset(assetValue, assetType); 
 }
 
 private void AddAssetToCollection(Asset a)
 {
   this.Assets.Add(a); 

   AccountingRules rules = this.IAccountingRulesRepo.GetByAssetID(assetType); 
   Account accountDebit = new Account(rules.DebitAccount); 
   Account accountCredit = new Account(rules.CreditAccount); 

   accountCredit.Credit(assetValue); 
   accountDebit.Debit(assetValue); 
}

private void Save()
{
    
   using (Transaction trans = this.IAccountingRulesRepo.StartTransaction())
   {
   try
   {
     this.IAccountRepo.Save(accountCredit); 
     this.IAccountRepo.Save(accountDebit); 
     trans.commit
  }
  except (exception e)
  {
    trans.rollback();
    throw;
  }
  }
 }
 }