Added MinBy, MaxBy, MinByOrDefault and MaxByOrDefault methods and replaced calls of the style OrderBy[Descending]().First[OrDefault]() which is not as performant.

OpenRA.Game/Exts.cs

@@ -131,6 +131,54 @@ namespace OpenRA
 			for (;;) { yield return t; t = f(t); }
 		}
 
+		public static T MinBy<T, U>(this IEnumerable<T> ts, Func<T, U> selector)
+		{
+			return ts.CompareBy(selector, 1, true);
+		}
+
+		public static T MaxBy<T, U>(this IEnumerable<T> ts, Func<T, U> selector)
+		{
+			return ts.CompareBy(selector, -1, true);
+		}
+
+		public static T MinByOrDefault<T, U>(this IEnumerable<T> ts, Func<T, U> selector)
+		{
+			return ts.CompareBy(selector, 1, false);
+		}
+
+		public static T MaxByOrDefault<T, U>(this IEnumerable<T> ts, Func<T, U> selector)
+		{
+			return ts.CompareBy(selector, -1, false);
+		}
+
+		static T CompareBy<T, U>(this IEnumerable<T> ts, Func<T, U> selector, int modifier, bool throws)
+		{
+			var comparer = Comparer<U>.Default;
+			T t;
+			U u;
+			using (var e = ts.GetEnumerator())
+			{
+				if (!e.MoveNext())
+					if (throws)
+						throw new ArgumentException("Collection must not be empty.", "ts");
+					else
+						return default(T);
+				t = e.Current;
+				u = selector(t);
+				while (e.MoveNext())
+				{
+					T nextT = e.Current;
+					U nextU = selector(nextT);
+					if (comparer.Compare(nextU, u) * modifier < 0)
+					{
+						t = nextT;
+						u = nextU;
+					}
+				}
+				return t;
+			}
+		}
+
 		public static int NextPowerOf2(int v)
 		{
 			--v;