I have the following function

public Dictionary<DateTime, object> GetAttributeList(
            EnumFactorType attributeType
            ,Thomson.Financial.Vestek.Util.DateRange dateRange)
        {
            DateTime startDate = dateRange.StartDate;
            DateTime endDate = dateRange.EndDate;            

           return ((
                //Step 1: Iterate over the attribute list and filter the records by
                // the supplied attribute type
                     from assetAttribute in AttributeCollection
                     where assetAttribute.AttributeType.Equals(attributeType)
                     //Step2:Assign the TimeSeriesData collection into a temporary variable 
                     let timeSeriesList = assetAttribute.TimeSeriesData
                     //Step 3: Iterate over the TimeSeriesData list and filter the records by
                     // the supplied date 
                     from timeSeries in timeSeriesList.ToList()
                     where timeSeries.Key >= startDate && timeSeries.Key <= endDate
                     //Finally build the needed  collection
                     select new AssetAttribute()
                     {
                         TimeSeriesData = PopulateTimeSeriesData(timeSeries.Key, timeSeries.Value)
                     }).ToList<AssetAttribute>().Select(i => i.TimeSeriesData));

        }

private Dictionary<DateTime, object> PopulateTimeSeriesData(DateTime dateTime, object value)
        {
            Dictionary<DateTime, object> timeSeriesData = new Dictionary<DateTime, object>();
            timeSeriesData.Add(dateTime, value);
            return timeSeriesData;
        }

Error:Cannot implicitly convert type 'System.Collections.Generic.IEnumerable>' to 'System.Collections.Generic.Dictionary'. An explicit conversion exists (are you missing a cast?)

Using C#3.0

Please help