示例工程版本提升至net462，项目添加了部分空引用检测逻辑。累了，消不完的空引用警告(T.T）

Net462DllTest/Signal/PLCVarSignal.cs

@@ -0,0 +1,64 @@
+using Serein.Library.Attributes;
+using System;
+using static Net462DllTest.Signal.PlcValueAttribute;
+
+namespace Net462DllTest.Signal
+{
+
+    [AttributeUsage(AttributeTargets.Field)]
+    public class PlcValueAttribute : Attribute
+    {
+        /// <summary>
+        /// 变量类型
+        /// </summary>
+        public enum VarType
+        {
+            /// <summary>
+            /// 只读取的值
+            /// </summary>
+            ReadOnly,
+            /// <summary>
+            /// 可写入的值
+            /// </summary>
+            Writable,
+        }
+        
+        /// <summary>
+        /// 变量属性
+        /// </summary>
+        public PlcVarInfo PlcInfo { get; }
+
+
+        public PlcValueAttribute(Type type,
+                                string @var,
+                                VarType varType
+                                )
+        {
+            PlcInfo = new PlcVarInfo(type, var, varType);
+        }
+    }
+
+    public class PlcVarInfo
+    {
+        public PlcVarInfo(Type type,
+                        string @var,
+                        VarType varType
+                        )
+        {
+            DataType = type;
+            VarAddress = @var;
+            Type = varType;
+        }
+        public bool IsProtected { get; }
+        public Type DataType { get; }
+        public string VarAddress { get; }
+        public VarType Type { get; }
+
+        public override string ToString()
+        {
+            return $"数据类型:{DataType} 地址:{VarAddress}";
+        }
+    }
+
+
+}