重写了节点的view、viewmodel关系，实现了对画布元素的选取功能，重构了底层依赖，添加了对net .Framework4.6.1以上的Framework类库支持

Library.Core/Flow/Tool/TcsSignal.cs

@@ -0,0 +1,80 @@
+using System.Collections.Concurrent;
+
+namespace Serein.Flow.Tool
+{
+    public class TcsSignalException : Exception
+    {
+        public FfState FfState { get; set; }
+        public TcsSignalException(string? message) : base(message)
+        {
+            FfState = FfState.Cancel;
+        }
+    }
+
+    public class TcsSignal<TSignal> where TSignal : struct, Enum
+    {
+
+        public ConcurrentDictionary<TSignal, Stack<TaskCompletionSource<object>>> TcsEvent { get; } = new();
+
+        // public object tcsObj = new object();
+
+        public bool TriggerSignal<T>(TSignal signal, T state)
+        {
+            if (TcsEvent.TryRemove(signal, out var waitTcss))
+            {
+                while (waitTcss.Count > 0)
+                {
+
+                    waitTcss.Pop().SetResult(state);
+
+                }
+                return true;
+            }
+            return false;
+
+
+        }
+        
+        public TaskCompletionSource<object> CreateTcs(TSignal signal)
+        {
+            
+            var tcs = new TaskCompletionSource<object>();
+            TcsEvent.GetOrAdd(signal, _ => new Stack<TaskCompletionSource<object>>()).Push(tcs);
+            return tcs;
+
+
+
+        }
+        //public TaskCompletionSource<object> GetOrCreateTcs(TSignal signal)
+        //{
+        //    lock (tcsObj)
+        //    {
+        //        var tcs = TcsEvent.GetOrAdd(signal, _ => new TaskCompletionSource<object>());
+        //        if (tcs.Task.IsCompleted)
+        //        {
+        //            TcsEvent.TryRemove(signal, out _);
+        //            tcs = new TaskCompletionSource<object>();
+        //            TcsEvent[signal] = tcs;
+        //        }
+        //        return tcs;
+        //    }
+        //}
+
+        public void CancelTask()
+        {
+            lock(TcsEvent)
+            {
+
+                foreach (var tcss in TcsEvent.Values)
+                {
+                    while (tcss.Count > 0)
+                    {
+                        tcss.Pop().SetException(new TcsSignalException("Task Cancel"));
+                    }
+                }
+                TcsEvent.Clear();
+            }
+        }
+
+    }
+}