流程返回值改为FlowResult，记录节点信息、上下文信息，为以后的流程调用回溯做准备

Library/FlowNode/FlowResult.cs

@@ -0,0 +1,97 @@
+using Serein.Library.Api;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reactive;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Serein.Library
+{
+    /// <summary>
+    /// 表示空数据
+    /// </summary>
+    /*public readonly struct Unit : IEquatable<Unit>
+    {
+        public static readonly Unit Default = default;
+        public bool Equals(Unit _) => true;
+        public override bool Equals(object obj) => obj is Unit;
+        public override int GetHashCode() => 0;
+    }*/
+
+
+    /// <summary>
+    /// 流程返回值的包装
+    /// </summary>
+    public class FlowResult
+    {
+        /// <summary>
+        /// 实例化返回值
+        /// </summary>
+        /// <param name="nodeModel"></param>
+        /// <param name="context"></param>
+        public FlowResult(NodeModelBase nodeModel, IDynamicContext context, object value)
+        {
+            this.NodeGuid = nodeModel.Guid;
+            this.ContextGuid = context.Guid;
+            this.Value = value;
+        }
+        /// <summary>
+        /// 空返回值
+        /// </summary>
+        /// <param name="nodeModel"></param>
+        /// <param name="context"></param>
+        public FlowResult(NodeModelBase nodeModel, IDynamicContext context)
+        {
+            this.NodeGuid = nodeModel.Guid;
+            this.ContextGuid = context.Guid;
+            this.Value  = Unit.Default;
+        }
+        /// <summary>
+        /// 尝试获取值
+        /// </summary>
+        /// <param name="targetType">目标类型</param>
+        /// <param name="value">返回值</param>
+        /// <returns>指示是否获取成功</returns>
+        /// <exception cref="ArgumentNullException">无法转为对应类型</exception>
+        public bool TryGetValue(Type targetType, out object value)
+        {
+            if (targetType is null)
+                throw new ArgumentNullException(nameof(targetType));
+
+            if (targetType.IsInstanceOfType(Value))
+            {
+                value = Value;
+                return true;
+            }
+
+            value = Unit.Default;
+            return false;
+        }
+
+
+
+        /// <summary>
+        /// 来源节点Guid
+        /// </summary>
+        public string NodeGuid { get; }
+        /// <summary>
+        /// 来源上下文Guid
+        /// </summary>
+        public string ContextGuid { get; } 
+        /// <summary>
+        /// 数据值
+        /// </summary>
+        public object Value { get; private set; }
+        /// <summary>
+        /// 生成时间
+        /// </summary>
+        public DateTime ResultTime { get; } = DateTime.MinValue;
+
+        /// <summary>
+        /// 是否自动回收
+        /// </summary>
+        public bool IsAutoRecovery { get; set; }
+
+    }
+}