ypu can use LINQ for this purpose, but i think this is fastest way as compare to LINQ
int minAccountLevel = int.MaxValue;
int maxAccountLevel = int.MinValue;
foreach (DataRow dr in table.Rows)
{
int accountLevel = dr.Field<int>("AccountLevel");
minAccountLevel = Math.Min(minAccountLevel, accountLevel);
maxAccountLevel = Math.Max(maxAccountLevel, accountLevel);
}