修改了logwindows输出，避免高频输出时卡死。修改了流程运行上下文，使节点具备终止分支运行的能力。

WorkBench.Remote/Node/ViewModel/ExpOpNodeViewModel.cs

@@ -0,0 +1,26 @@
+using Serein.NodeFlow.Model;
+using Serein.WorkBench.Node.View;
+
+namespace Serein.WorkBench.Node.ViewModel
+{
+    public class ExpOpNodeViewModel: NodeControlViewModelBase
+    {
+        public readonly SingleExpOpNode node;
+
+        public string Expression
+        {
+            get => node.Expression;
+            set
+            {
+                node.Expression = value;
+                OnPropertyChanged();
+            }
+        }
+
+
+        public ExpOpNodeViewModel(SingleExpOpNode node) : base(node)
+        { 
+            this.node = node;
+        }
+    }
+}