} // end method
private static object FindExtreme(IEnumerable enumerable, ref SystemTool.Comparison comparison, bool max) {
object extreme = null;
var isDefaultComparison = comparison == SystemTool.Comparison.Default; // indicates if the original comparsion value is Default
var isEverDefault = false; // indicates if any comparison is ever Default
var isEverNumeric = false; // indicates if any comparison is ever Numeric
var isFirst = true; // flag for processing the first item in enumerable
var isStringCheckDone = false; // flag for indicating if all the items in enumerable were checked for String comparison
// Loop through all the items in enumerable. If comparison is either String
// or Numeric, just perform the comparison, look at the result and set extreme
// if necessary. For Default comparisons, special logic is necessary (see
// comment for isDefaultComparison if statement below).
foreach (var item in enumerable) {
if (isFirst) {
isFirst = false;
extreme = item;
continue;
} // end if
// (Non-Default comparisons are easy. Just perform the comparison.
// For Default, perform the check and then examine the comparison
// value afterwards. If its String, just return FindExtreme passing
// comparison of String. If its Default, make note that a Default
// comparison was used by setting isEverDefault to true;
// If its numeric, make note that a Numeric comparison was used
// by setting isEverNumeric to true. Then, if it hasn't already
// been done (via isStingCheckDone), compare all the values
// to the number 0 with a Default comparison to see if any rely
// on a String comparison. If they do, just return FindExtreme
// passing comparison of String. If no String comparisons occur,
// then either Default only or Numeric only comparisons are safe.
int compResult;
if (isDefaultComparison) {
comparison = SystemTool.Comparison.Default;
compResult = item.CompareTo(extreme, ref comparison);
if (comparison == SystemTool.Comparison.String)
return FindExtreme(enumerable, ref comparison, max);
if (comparison == SystemTool.Comparison.Default)
isEverDefault = true;
if (comparison == SystemTool.Comparison.Numeric) {
isEverNumeric = true;
if (!isStringCheckDone) {
foreach (var e in enumerable) {
comparison = SystemTool.Comparison.Default;
e.CompareTo(0, ref comparison);
if (comparison == SystemTool.Comparison.String)
return FindExtreme(enumerable, ref comparison, max);
} // end foreach
isStringCheckDone = true;
} // end if
} // end if
} else
compResult = item.CompareTo(extreme, ref comparison);
if (max && compResult > 0 || !max && compResult < 0)
extreme = item;
} // end foreach
// At this point, there are no String comparisons. At this point,
// if there was ever a Default comparison and also a Numeric comparison,
// it is necessary to repeat FindExtreme call but this time with
// an explicit Numeric comparison in case mixed objects that are Comparable
// (Default comparison) do not compare the same way numerically.
if (isEverNumeric && isEverDefault) {
comparison = SystemTool.Comparison.Numeric;
return FindExtreme(enumerable, ref comparison, max);
} // end if
return extreme;
} // end method
} // end method
public static object FindMin(this IEnumerable enumerable, ref SystemTool.Comparison comparison) {
return FindExtreme(enumerable, ref comparison, false);
} // end method
