fix

Author: linzhijun

csharp/ToolGood.Algorithm/Internals/Functions/MathSum/Function_MODE.cs

@@ -29,7 +29,15 @@ public override Operand Evaluate(AlgorithmEngine engine, Func<AlgorithmEngine, s
                     dict[item] = 1;
                 }
             }
-            return Operand.Create(dict.OrderByDescending(q => q.Value).First().Key);
+            decimal modeKey = 0;
+            int maxCount = 0;
+            foreach (var kvp in dict) {
+                if (kvp.Value > maxCount) {
+                    maxCount = kvp.Value;
+                    modeKey = kvp.Key;
+                }
+            }
+            return Operand.Create(modeKey);
         }
 
     }

csharp/ToolGood.Algorithm/Operand.cs

@@ -35,6 +35,16 @@ public abstract class Operand
 		/// Zero
 		/// </summary>
 		public static readonly Operand Zero = Operand.Create(0m);
+		/// <summary>
+		/// Null
+		/// </summary>
+		public static readonly Operand Null = new OperandNull();
+		private static readonly Operand[] IntCache = new Operand[256];
+		static Operand()
+		{
+			for (int i = 0; i < 256; i++)
+				IntCache[i] = new OperandInt(i - 128);
+		}
 
 		#region  IsNull IsNumber IsText IsBoolean IsArray IsDate IsJson IsArrayJson IsError ErrorMsg
 		/// <summary>
@@ -161,6 +171,8 @@ public static Operand Create(short obj)
 		/// <returns></returns>
 		public static Operand Create(int obj)
 		{
+			if (obj >= -128 && obj <= 127)
+				return IntCache[obj + 128];
 			return new OperandInt(obj);
 		}
 
@@ -395,10 +407,7 @@ public static Operand Error(string msg, params object[] args)
 		/// 创建操作数
 		/// </summary>
 		/// <returns></returns>
-		public static Operand CreateNull()
-		{
-			return new OperandNull();
-		}
+		public static Operand CreateNull() => Null;
 
 		#endregion Create