序列化bug修复，近期主要修复bug为主

AIStudio.Wpf.Mind/Models/MindNodeDesignerItem.cs

@@ -18,20 +18,34 @@ namespace AIStudio.Wpf.Mind.Models
         }
         public MindNodeDesignerItem(MindNode item) : base(item)
         {
+            MindType = item.MindType;
+            MindTheme = item.MindTheme;
             Spacing = item.Spacing;
             Offset = item.Offset;
             IsExpanded = item.IsExpanded;
             LinkInfoItem = new LinkInfoItem(item.LinkInfo);
             ImageInfoItem = new ImageInfoItem(item.ImageInfo);
             Remark = item.Remark;
-            Priority= item.Priority;
-            Rate=item.Rate;
+            Priority= item.Priority?.ToString();
+            Rate=item.Rate.ToString();
             if (item.Tags != null)
             {
                 Tags = new List<string>(item.Tags);
             }
         }
 
+        [XmlAttribute]
+        public MindType MindType
+        {
+            get; set;
+        }
+
+        [XmlAttribute]
+        public MindTheme MindTheme
+        {
+            get; set;
+        }
+
         [XmlIgnore]
         public Size Spacing
         {
@@ -90,18 +104,18 @@ namespace AIStudio.Wpf.Mind.Models
         {
             get; set;
         }
-
+        [XmlAttribute]
         public string Remark
         {
             get; set;
         }
-
-        public double? Priority
+        [XmlAttribute]
+        public string Priority
         {
             get; set;
         }
-
-        public double? Rate
+        [XmlAttribute]
+        public string Rate
         {
             get; set;
         }