结构调整，便于后续扩展

AIStudio.Wpf.BaseDiagram/Converters/ThicknessConverter.cs

@@ -0,0 +1,59 @@
+using System;
+using System.Globalization;
+using System.Windows;
+using System.Windows.Data;
+
+namespace AIStudio.Wpf.BaseDiagram.Converters
+{
+    public class ThicknessToDoubleConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            return ((Thickness)value).Left;
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            return DependencyProperty.UnsetValue;
+        }
+    }
+
+    internal class DoubleToRightMarginConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            return new Thickness(0, 0, ((double)value), 0);
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            return DependencyProperty.UnsetValue;
+        }
+    }
+
+    internal class DoubleToLeftMarginConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            return new Thickness(((double)value), 0, 0, 0);
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            return DependencyProperty.UnsetValue;
+        }
+    }
+
+    internal class DoubleToLeftRightMarginConverter : IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            return new Thickness((double)value, 0, (double)value, 0);
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            return DependencyProperty.UnsetValue;
+        }
+    }
+}