To answer Mike's original question, I've expanded the snippet he posted to extract the calculation results. Here is the code:
// Calculate Statistics
IReadOnlyList<TableStatisticsResult> tableStatisticsResults = countryFeatureClass.CalculateStatistics(tableStatisticsDescription);
foreach(TableStatisticsResult tableStatisticsResult in tableStatisticsResults)
{
// Get the Region name
// If multiple fields had been passed into TableStatisticsDescription.GroupBy, there
// would be multiple values in TableStatisticsResult.GroupBy
string regionName = tableStatisticsResult.GroupBy.First().Value.ToString();
// Get the statistics results for the Population_1990 field
StatisticsResult pop1990Statistics = tableStatisticsResult.StatisticsResults[0];
double population1990Sum = pop1990Statistics.Sum;
double population1990Average = pop1990Statistics.Average;
// Get the statistics results for the Population_2000 field
StatisticsResult pop2000Statistics = tableStatisticsResult.StatisticsResults[1];
double population2000Sum = pop2000Statistics.Sum;
double population2000Average = pop2000Statistics.Average;
// Do something with the results here...
}
I hope this helps.