添加PreEvaluateVariableEnable配置，读取表达式/写入表达式中可以用变量名称获取全局变量的值，因性能问题默认关闭

src/ThingsGateway.Gateway.Application/Config/Gateway.Development.json

@@ -6,5 +6,8 @@
   },
   "ChannelThread": {
     "CycleInterval": 20 //最小循环间隔
+  },
+  "ExpressionEvaluator": {
+    "PreEvaluateVariableEnable": false //启用后，读取表达式/写入表达式中可以用变量名称获取全局变量的值
   }
 }

src/ThingsGateway.Gateway.Application/Config/Gateway.Production.json

@@ -6,5 +6,8 @@
   },
   "ChannelThread": {
     "CycleInterval": 20 //最小循环间隔
+  },
+  "ExpressionEvaluator": {
+    "PreEvaluateVariableEnable": false //启用后，读取表达式/写入表达式中可以用变量名称获取全局变量的值
   }
 }

src/ThingsGateway.Gateway.Application/Extensions/ExpressionEvaluatorExtension.cs

@@ -19,6 +19,7 @@ namespace ThingsGateway.Gateway.Application.Extensions;
 public static class ExpressionEvaluatorExtension
 {
     private static readonly GlobalData GlobalData = App.RootServices.GetService<GlobalData>();
+    private static bool PreEvaluateVariableEnable = App.GetConfig<bool?>("ExpressionEvaluator:PreEvaluateVariable") ?? false;
 
     /// <summary>
     /// 计算表达式：例如：raw*100，raw为原始值
@@ -41,7 +42,8 @@ public static class ExpressionEvaluatorExtension
         //
         ExpressionEvaluator expressionEvaluator = new();
         expressionEvaluator.OptionScriptNeedSemicolonAtTheEndOfLastExpression = false;
-        expressionEvaluator.PreEvaluateVariable += Evaluator_PreEvaluateVariable;
+        if (PreEvaluateVariableEnable)
+            expressionEvaluator.PreEvaluateVariable += Evaluator_PreEvaluateVariable;
         expressionEvaluator.Assemblies.Add(typeof(Newtonsoft.Json.JsonConverter).Assembly);
         expressionEvaluator.Namespaces.Add("Newtonsoft.Json.Linq");
         expressionEvaluator.Namespaces.Add("Newtonsoft.Json");