int m = consumptionResult.Sites.Count;

            double[] sum = new double[consumptionResult.Sites.Count];
            for (int i = 0; i < m; i++)
            {
                for (int j = 0; j < consumptionResult.Sites[i].Actual.Count; j++)
                {
                    sum[i] += consumptionResult.Sites[i].Actual[j];
                }

            }


ERROR MESSAGE:
Cannot implicitly convert type 'double?' to 'double'. An explicit conversion exists (are you missing a cast?)
Cannot convert source type `System.Nullable<double>' to target type 'double'