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/DbSql/FifoManualResetEvent.cs

@@ -0,0 +1,71 @@
+namespace Serein.DbSql
+{
+    /// <summary>
+    /// 线程阻塞
+    /// </summary>
+    public class FifoManualResetEvent
+    {
+        private readonly object lockObj = new object();
+        /// <summary>
+        /// 让线程按进入时间顺序调用
+        /// </summary>
+        private readonly Queue<Thread> waitQueue = new Queue<Thread>();
+        private bool isSet;
+
+        public bool IsSet { get => isSet; set => isSet = value; }
+
+        public FifoManualResetEvent(bool initialState = false)
+        {
+            IsSet = initialState;
+        }
+
+        /// <summary>
+        /// 等待解锁
+        /// </summary>
+        public void Wait()
+        {
+            lock (lockObj)
+            {
+                if (IsSet)
+                {
+                    // 获取到了发送的信号，线程开始重新执行
+                    return;
+                }
+
+                var currentThread = Thread.CurrentThread;
+                waitQueue.Enqueue(currentThread);
+
+                while (!IsSet || waitQueue.Peek() != currentThread)
+                {
+                    Monitor.Wait(lockObj);
+                }
+
+                waitQueue.Dequeue();
+            }
+        }
+
+        /// <summary>
+        /// 发送信号
+        /// </summary>
+        public void Set()
+        {
+            lock (lockObj)
+            {
+                IsSet = true;
+                Monitor.PulseAll(lockObj);
+            }
+        }
+
+        /// <summary>
+        /// 锁定当前线程
+        /// </summary>
+        public void Reset()
+        {
+            lock (lockObj)
+            {
+                IsSet = false;
+            }
+        }
+    }
+
+}