简单实现变量的历史记录功能

ValueConverts/NullableBooleanConverter.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Globalization;
+using System.Windows.Data;
+
+namespace PMSWPF.ValueConverts
+{
+    public class NullableBooleanConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            if (value is bool b && parameter is string paramString)
+            {
+                if (bool.TryParse(paramString, out bool paramBool))
+                {
+                    return b == paramBool;
+                }
+            }
+            return Binding.DoNothing;
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            if (value is bool b && b && parameter is string paramString)
+            {
+                if (bool.TryParse(paramString, out bool paramBool))
+                {
+                    return paramBool;
+                }
+            }
+            return Binding.DoNothing;
+        }
+    }
+}