Parallel class in C# - c#-4.0

Question

i am copying one object to another using for loop which is dependent on noOFResults. I replaced Foreach loop by Parallel.For to increase the performance but the same cause major performance degrade. So I want to understand what is the cause of this ??
int resultCount = 0;
var apiSearchResults = new PS_HotelSearchResult[results.Count];
foreach (BE_HotelSearchResult result in results)
{
apiSearchResults[resultCount] = new PS_HotelSearchResult();
#region Fields of First Search
apiSearchResults[resultCount].RateType = (PS_RateType)result.RateType;
apiSearchResults[resultCount].HotelCode = result.HotelCode;
apiSearchResults[resultCount].Discount = result.AmountBeforeDiscountInSupplierCurr -
result.AmountAfterTaxInSupplierCurr;
apiSearchResults[resultCount].AmountAfterTax = result.AmountAfterTaxInSupplierCurr;
apiSearchResults[resultCount].AmountBeforeTax = result.AmountBeforeTaxInSupplierCurr;
apiSearchResults[resultCount].Currency = result.CurrencySupplier;
apiSearchResults[resultCount].IsUniversalApiResult = true;
if (result.Price != null)
{
apiSearchResults[resultCount].TotalGP = result.Price.TotalGP;
}
#endregion
#region Fields for Room
if (!Equals(result.RoomDetails, null))
{
int roomCount = 0;
apiSearchResults[resultCount].RoomDetails =
new PS_HotelRoomsDetails[result.RoomDetails.Length];
foreach (BE_HotelRoomsDetails roomDetail in result.RoomDetails)
{
if (roomDetail.CancellationPolicies == null)
{
throw new BusinessServiceException("HotelPrice.GetPrice - CancellationPolicies SHOULD NOT BE Null for rooms");
}
apiSearchResults[resultCount].RoomDetails[roomCount] = new PS_HotelRoomsDetails
{
SequenceNo = roomDetail.SequenceNo,
#region ExtraGuestCharge and ChildCharges
// Multiplied by number of nights becuase its a day wise price and we are setting it roomwise
SellExtraGuestCharges = roomDetail.SellExtraGuestCharges,
PubExtraGuestCharges = roomDetail.PubExtraGuestCharges,
ChildCharges = roomDetail.ChildCharges,
SellChildCharges = roomDetail.SellChildCharges,
#endregion
#region Discount and Tax
Discount = roomDetail.Discount,
TotalTax = roomDetail.TotalTax,
#endregion
};
int k = 0;
#region DayWiseRate
if (!Equals(roomDetail.Rates, null))
{
apiSearchResults[resultCount].RoomDetails[roomCount].Rates =
new PS_RoomRates[roomDetail.Rates.Length];
foreach (BE_RoomRates rate in roomDetail.Rates)
{
apiSearchResults[resultCount].RoomDetails[roomCount].Rates[k] = new PS_RoomRates
{
Amount = rate.Amount,
//Pricing is wrong
//SellingFare = rate.SellingFare
};
k++;
}
}
#endregion
k = 0;
#region Additional Charges
if (!Equals(roomDetail.AdditionalCharges, null))
{
apiSearchResults[resultCount].RoomDetails[roomCount].AdditionalCharges =
new PS_AdditionalCharges[roomDetail.AdditionalCharges.Count];
foreach (
BE_AdditionalCharges additionalCharge in
roomDetail.AdditionalCharges)
{
apiSearchResults[resultCount].RoomDetails[roomCount].AdditionalCharges[k] = new PS_AdditionalCharges
{
Charge = additionalCharge.Charge,
IncludedInTotal = additionalCharge.IncludedInTotal
};
k++;
}
}
#endregion
#region Price and Price Component
apiSearchResults[resultCount].RoomDetails[roomCount].Price = new HotelPriceAccounts();
if (!Equals(roomDetail.Price, null))
{
apiSearchResults[resultCount].RoomDetails[roomCount].Price.Discount = roomDetail.Price.Discount;
apiSearchResults[resultCount].RoomDetails[roomCount].Price.PublishedFare = roomDetail.Price.PublishedFare;
apiSearchResults[resultCount].RoomDetails[roomCount].Price.Tax = roomDetail.Price.Tax;
apiSearchResults[resultCount].RoomDetails[roomCount].Price.OtherCharge = roomDetail.Price.OtherCharges;
apiSearchResults[resultCount].RoomDetails[roomCount].Price.TotalGP = roomDetail.Price.TotalGP;
apiSearchResults[resultCount].RoomDetails[roomCount].Price.IsGPEnabled = roomDetail.Price.IsGPEnabled;
apiSearchResults[resultCount].RoomDetails[roomCount].Price.AgentMarkUpType =
(AgentMarkUpType)roomDetail.Price.AgentMarkUpType;
apiSearchResults[resultCount].RoomDetails[roomCount].Price.PriceId = roomDetail.Price.PriceId;
}
#endregion
roomCount++;
}
}

Answer 1

There are no for loops in the code, just foreach loops.
Do not expect loops to be automatically faster when using Parallel.For.
Especially when iterations have effect on the outer scope, the iterations can hardly be run in parallel. So all you are adding is overhead to split the iterations across tasks.
The outer scope is affected by changing Amount. k and apiSearchResults inside of the loops, just to name a few.