diff --git a/AIStudio.Wpf.DiagramDesigner/Converters/NullableToVisibilityConverter.cs b/AIStudio.Wpf.DiagramDesigner/Converters/NullableToVisibilityConverter.cs
new file mode 100644
index 0000000..94389a3
--- /dev/null
+++ b/AIStudio.Wpf.DiagramDesigner/Converters/NullableToVisibilityConverter.cs
@@ -0,0 +1,25 @@
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Text;
+using System.Windows.Data;
+using System.Windows;
+
+namespace AIStudio.Wpf.DiagramDesigner
+{
+    public class NullableToVisibilityConverter : IValueConverter
+    {
+        public Visibility NullValue { get; set; } = Visibility.Collapsed;
+        public Visibility NotNullValue { get; set; } = Visibility.Visible;
+
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            return value == null ? NullValue : NotNullValue;
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            return Binding.DoNothing;
+        }
+    }
+}
diff --git a/AIStudio.Wpf.Mind/AIStudio.Wpf.Mind.csproj b/AIStudio.Wpf.Mind/AIStudio.Wpf.Mind.csproj
index 3a8d4f8..a978cf4 100644
--- a/AIStudio.Wpf.Mind/AIStudio.Wpf.Mind.csproj
+++ b/AIStudio.Wpf.Mind/AIStudio.Wpf.Mind.csproj
@@ -9,7 +9,7 @@
     <PackageIconUrl />
     <NeutralLanguage />
     <Version>1.0.6</Version>
-    <Description>一个Wpf的流程图控件</Description>
+    <Description>一个Wpf的思维导图控件</Description>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/AIStudio.Wpf.Mind/Controls/PriorityControl.xaml.cs b/AIStudio.Wpf.Mind/Controls/PriorityControl.xaml.cs
index 61717f8..a0637f9 100644
--- a/AIStudio.Wpf.Mind/Controls/PriorityControl.xaml.cs
+++ b/AIStudio.Wpf.Mind/Controls/PriorityControl.xaml.cs
@@ -27,15 +27,15 @@ namespace AIStudio.Wpf.Mind.Controls
 
         /// <summary>Identifies the <see cref="Priority"/> dependency property.</summary>
         public static readonly DependencyProperty PriorityProperty
-            = DependencyProperty.Register(nameof(Priority), typeof(double), typeof(PriorityControl));
+            = DependencyProperty.Register(nameof(Priority), typeof(double?), typeof(PriorityControl));
 
         /// <summary> 
         /// Whether or not the "popup" menu for this control is currently open
         /// </summary>
-        public double Priority
+        public double? Priority
         {
-            get => (double)this.GetValue(PriorityProperty);
-            set => this.SetValue(PriorityProperty, (double)value);
+            get => (double?)this.GetValue(PriorityProperty);
+            set => this.SetValue(PriorityProperty, (double?)value);
         }
     }
 }
diff --git a/AIStudio.Wpf.Mind/Controls/RateControl.xaml b/AIStudio.Wpf.Mind/Controls/RateControl.xaml
index 8494db3..26b9ee1 100644
--- a/AIStudio.Wpf.Mind/Controls/RateControl.xaml
+++ b/AIStudio.Wpf.Mind/Controls/RateControl.xaml
@@ -4,11 +4,66 @@
 
 
     <Style x:Key="RateControlStyle" TargetType="{x:Type controls:RateControl}">
+        <Setter Property="Background" Value="Yellow" />
+        <Setter Property="Foreground" Value="Green" />
+        <Setter Property="BorderBrush" Value="Transparent"/>
+        <Setter Property="BorderThickness" Value="1"/>
+        <Setter Property="Padding" Value="3" />
         <Setter Property="Template">
             <Setter.Value>
                 <ControlTemplate TargetType="{x:Type controls:RateControl}">
-                    <Grid>
+                    <Grid x:Name="RootGrid">
+                        <Ellipse Fill="{TemplateBinding Background}" 
+                                 Stroke="{TemplateBinding BorderBrush}" 
+                                 StrokeThickness="{TemplateBinding BorderThickness}"
+                                 x:Name="border">
+                        </Ellipse>
+                        <Path x:Name="Path" Stretch="Uniform" Fill="{TemplateBinding Foreground}" 
+                                  RenderTransformOrigin="0.5,0.5" 
+                                  Data="">
+                            <Path.RenderTransform>
+                                <ScaleTransform ScaleY="-1"/>
+                            </Path.RenderTransform>
+                        </Path>
                     </Grid>
+                    <ControlTemplate.Triggers>
+                        <Trigger Property="Rate" Value="0">
+                            <Setter TargetName="Path" Property="Data" Value="M256 8C119 8 8 119 8 256s111 248 248 248 248-111 248-248S393 8 256 8zm0 448c-110.5 0-200-89.5-200-200S145.5 56 256 56s200 89.5 200 200-89.5 200-200 200z"/>
+                            <Setter Property="Background" Value="Red"/>
+                        </Trigger>
+                        <Trigger Property="Rate" Value="0.125">
+                            <Setter TargetName="Path" Property="Data" Value="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C13.93 5 15.68 5.78 16.95 7.05L12 12V5Z"/>
+                            <Setter Property="Background" Value="Blue"/>
+                        </Trigger>
+                        <Trigger Property="Rate" Value="0.25">
+                            <Setter TargetName="Path" Property="Data" Value="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C15.87 5 19 8.13 19 12H12V5Z"/>
+                            <Setter Property="Background" Value="Green"/>
+                        </Trigger>
+                        <Trigger Property="Rate" Value="0.375">
+                            <Setter TargetName="Path" Property="Data" Value="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C15.87 5 19 8.13 19 12C19 13.93 18.22 15.68 16.95 16.95L12 12V5Z"/>
+                            <Setter Property="Background" Value="Orange"/>
+                        </Trigger>
+                        <Trigger Property="Rate" Value="0.5">
+                            <Setter TargetName="Path" Property="Data" Value="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C15.87 5 19 8.13 19 12C19 15.87 15.87 19 12 19V5Z"/>
+                            <Setter Property="Background" Value="Purple"/>
+                        </Trigger>
+                        <Trigger Property="Rate" Value="0.625">
+                            <Setter TargetName="Path" Property="Data" Value="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C15.87 5 19 8.13 19 12C19 15.87 15.87 19 12 19C10.07 19 8.32 18.22 7.05 16.95L12 12V5Z"/>
+                            <Setter Property="Background" Value="Gray"/>
+                        </Trigger>
+                        <Trigger Property="Rate" Value="0.75">
+                            <Setter TargetName="Path" Property="Data" Value="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C15.87 5 19 8.13 19 12C19 15.87 15.87 19 12 19C8.13 19 5 15.87 5 12H12V5Z"/>
+                            <Setter Property="Background" Value="Gray"/>
+                        </Trigger>
+                        <Trigger Property="Rate" Value="0.875">
+                            <Setter TargetName="Path" Property="Data" Value="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C15.87 5 19 8.13 19 12C19 15.87 15.87 19 12 19C8.13 19 5 15.87 5 12C5 10.07 5.78 8.32 7.05 7.05L12 12V5Z"/>
+                            <Setter Property="Background" Value="Gray"/>
+                        </Trigger>
+                        <Trigger Property="Rate" Value="1">
+                            <Setter TargetName="Path" Property="Data" Value="m 256,76 c 48.1,0 93.3,18.7 127.3,52.7 34,34 52.7,79.2 52.7,127.3 0,48.1 -18.7,93.3 -52.7,127.3 -34,34 -79.2,52.7 -127.3,52.7 -48.1,0 -93.3,-18.7 -127.3,-52.7 C 94.7,349.3 76,304.1 76,256 76,207.9 94.7,162.7 128.7,128.7 162.7,94.7 207.9,76 256,76 m 0,-28 C 141.1,48 48,141.1 48,256 48,370.9 141.1,464 256,464 370.9,464 464,370.9 464,256 464,141.1 370.9,48 256,48 Z M 362.6,192.9 345,174.8 c -0.7,-0.8 -1.8,-1.2 -2.8,-1.2 -1.1,0 -2.1,0.4 -2.8,1.2 L 217.4,297.7 173,253.3 c -0.8,-0.8 -1.8,-1.2 -2.8,-1.2 -1,0 -2,0.4 -2.8,1.2 l -17.8,17.8 c -1.6,1.6 -1.6,4.1 0,5.7 l 56,56 c 3.6,3.6 8,5.7 11.7,5.7 5.3,0 9.9,-3.9 11.6,-5.5 H 229 L 362.7,198.6 c 1.4,-1.7 1.4,-4.2 -0.1,-5.7 z"/>
+                            <Setter Property="Background" Value="Gray"/>
+                        </Trigger>
+                    </ControlTemplate.Triggers>
                 </ControlTemplate>
             </Setter.Value>
         </Setter>
diff --git a/AIStudio.Wpf.Mind/Controls/RateControl.xaml.cs b/AIStudio.Wpf.Mind/Controls/RateControl.xaml.cs
index f0dc29a..1f34fd5 100644
--- a/AIStudio.Wpf.Mind/Controls/RateControl.xaml.cs
+++ b/AIStudio.Wpf.Mind/Controls/RateControl.xaml.cs
@@ -27,15 +27,15 @@ namespace AIStudio.Wpf.Mind.Controls
 
         /// <summary>Identifies the <see cref="Rate"/> dependency property.</summary>
         public static readonly DependencyProperty RateProperty
-            = DependencyProperty.Register(nameof(Rate),  typeof(double), typeof(RateControl));
+            = DependencyProperty.Register(nameof(Rate),  typeof(double?), typeof(RateControl));
 
         /// <summary> 
         /// Whether or not the "popup" menu for this control is currently open
         /// </summary>
-        public double Rate
+        public double? Rate
         {
-            get => (double)this.GetValue(RateProperty);
-            set => this.SetValue(RateProperty, (double)value);
+            get => (double?)this.GetValue(RateProperty);
+            set => this.SetValue(RateProperty, (double?)value);
         }
     }
 }
diff --git a/AIStudio.Wpf.Mind/Controls/ToolBoxControl.xaml b/AIStudio.Wpf.Mind/Controls/ToolBoxControl.xaml
index eda249f..15854a9 100644
--- a/AIStudio.Wpf.Mind/Controls/ToolBoxControl.xaml
+++ b/AIStudio.Wpf.Mind/Controls/ToolBoxControl.xaml
@@ -155,7 +155,7 @@
                                 Width="20"
                                 Height="20"                                
                                 Command="{Binding AddPriorityCommand}"
-                                CommandParameter="0">
+                                CommandParameter="Null">
                             <Path Stretch="Uniform" Fill="DarkRed" Data="M966.4 761.6l-140.8 140.8-313.6-320-313.6 320-140.8-140.8 320-313.6-320-313.6 140.8-140.8 313.6 320 313.6-320 140.8 140.8-320 313.6z"></Path>
                         </Button>
 
@@ -278,59 +278,70 @@
                         <Button Style="{StaticResource FlatCircleButtonStyle}"
                                 Background="Yellow"
                                 Margin="1"
-                                Command="{Binding EditCommand}">
+                                Command="{Binding AddRatioCommand}"
+                                CommandParameter="Null">
                             <Path  Stretch="Uniform" Fill="DarkRed" Data="m 256,76 c 48.1,0 93.3,18.7 127.3,52.7 34,34 52.7,79.2 52.7,127.3 0,48.1 -18.7,93.3 -52.7,127.3 -34,34 -79.2,52.7 -127.3,52.7 -48.1,0 -93.3,-18.7 -127.3,-52.7 C 94.7,349.3 76,304.1 76,256 76,207.9 94.7,162.7 128.7,128.7 162.7,94.7 207.9,76 256,76 m 0,-28 C 141.1,48 48,141.1 48,256 48,370.9 141.1,464 256,464 370.9,464 464,370.9 464,256 464,141.1 370.9,48 256,48 Z m 75.3,260.7 -52.7,-52.7 52.7,-52.7 c 6.2,-6.2 6.2,-16.4 0,-22.6 -6.2,-6.2 -16.4,-6.2 -22.6,0 L 256,233.4 203.3,180.7 c -6.2,-6.2 -15.6,-7.1 -22.6,0 -7.1,7.1 -6,16.6 0,22.6 l 52.7,52.7 -52.7,52.7 c -6.7,6.7 -6.4,16.3 0,22.6 6.4,6.4 16.4,6.2 22.6,0 l 52.7,-52.7 52.7,52.7 c 6.2,6.2 16.4,6.2 22.6,0 6.3,-6.2 6.3,-16.4 0,-22.6 z"></Path>
                         </Button>
                         <Button Style="{StaticResource FlatCircleButtonStyle}"                 
                                 Background="Yellow"
                                 Margin="1"
-                                Command="{Binding EditCommand}">
+                                Command="{Binding AddRatioCommand}"
+                                CommandParameter="0">
                             <Path Stretch="Uniform" Fill="Green" Data="M256 8C119 8 8 119 8 256s111 248 248 248 248-111 248-248S393 8 256 8zm0 448c-110.5 0-200-89.5-200-200S145.5 56 256 56s200 89.5 200 200-89.5 200-200 200z"></Path>
                         </Button>
                         <Button Style="{StaticResource FlatCircleButtonStyle}"                 
                                 Background="Yellow"
                                 Margin="1"
-                                Command="{Binding EditCommand}">
+                                Command="{Binding AddRatioCommand}"
+                                CommandParameter="0.125">
                             <Path Stretch="Uniform" Fill="Green" Data="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C13.93 5 15.68 5.78 16.95 7.05L12 12V5Z"></Path>
                         </Button>
                         <Button Style="{StaticResource FlatCircleButtonStyle}"                 
                                 Background="Yellow"
-                                Command="{Binding EditCommand}">
+                                Command="{Binding AddRatioCommand}"
+                                CommandParameter="0.25">
                             <Path Stretch="Uniform" Fill="Green" Data="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C15.87 5 19 8.13 19 12H12V5Z"></Path>
                         </Button>
                         <Button Style="{StaticResource FlatCircleButtonStyle}"                 
                                 Background="Yellow" 
                                 Margin="1"
-                                Command="{Binding EditCommand}">
+                                Command="{Binding AddRatioCommand}"
+                                CommandParameter="0.375">
                             <Path Stretch="Uniform" Fill="Green" Data="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C15.87 5 19 8.13 19 12C19 13.93 18.22 15.68 16.95 16.95L12 12V5Z"></Path>
                         </Button>
                         <Button Style="{StaticResource FlatCircleButtonStyle}"                 
                                 Background="Yellow"
                                 Margin="1"
-                                Command="{Binding EditCommand}">
+                                Command="{Binding AddRatioCommand}"
+                                CommandParameter="0.5">
                             <Path Stretch="Uniform" Fill="Green" Data="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C15.87 5 19 8.13 19 12C19 15.87 15.87 19 12 19V5Z"></Path>
                         </Button>
                         <Button Style="{StaticResource FlatCircleButtonStyle}"                 
                                 Background="Yellow" 
-                                Command="{Binding EditCommand}">
+                                Margin="1"
+                                Command="{Binding AddRatioCommand}"
+                                CommandParameter="0.625">
                             <Path Stretch="Uniform" Fill="Green" Data="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C15.87 5 19 8.13 19 12C19 15.87 15.87 19 12 19C10.07 19 8.32 18.22 7.05 16.95L12 12V5Z"></Path>
                         </Button>
                         <Button Style="{StaticResource FlatCircleButtonStyle}"                 
                                 Background="Yellow"
                                 Margin="1"
-                                Command="{Binding EditCommand}">
+                                Command="{Binding AddRatioCommand}"
+                                CommandParameter="0.75">
                             <Path Stretch="Uniform" Fill="Green" Data="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C15.87 5 19 8.13 19 12C19 15.87 15.87 19 12 19C8.13 19 5 15.87 5 12H12V5Z"></Path>
                         </Button>
                         <Button Style="{StaticResource FlatCircleButtonStyle}"                 
                                 Background="Yellow"
                                 Margin="1"
-                                Command="{Binding EditCommand}">
+                                Command="{Binding AddRatioCommand}"
+                                CommandParameter="0.875">
                             <Path Stretch="Uniform" Fill="Green" Data="M12 2C17.5 2 22 6.5 22 12C22 17.5 17.5 22 12 22C6.5 22 2 17.5 2 12C2 6.5 6.5 2 12 2M12 4C7.58 4 4 7.58 4 12C4 16.42 7.58 20 12 20C16.42 20 20 16.42 20 12C20 7.58 16.42 4 12 4M12 5C15.87 5 19 8.13 19 12C19 15.87 15.87 19 12 19C8.13 19 5 15.87 5 12C5 10.07 5.78 8.32 7.05 7.05L12 12V5Z"></Path>
                         </Button>
                         <Button Style="{StaticResource FlatCircleButtonStyle}"                 
                                 Background="Yellow"
                                 Margin="1"
-                                Command="{Binding EditCommand}">
+                                Command="{Binding AddRatioCommand}"
+                                CommandParameter="1">
                             <Path Stretch="Uniform" Fill="Green" Data="m 256,76 c 48.1,0 93.3,18.7 127.3,52.7 34,34 52.7,79.2 52.7,127.3 0,48.1 -18.7,93.3 -52.7,127.3 -34,34 -79.2,52.7 -127.3,52.7 -48.1,0 -93.3,-18.7 -127.3,-52.7 C 94.7,349.3 76,304.1 76,256 76,207.9 94.7,162.7 128.7,128.7 162.7,94.7 207.9,76 256,76 m 0,-28 C 141.1,48 48,141.1 48,256 48,370.9 141.1,464 256,464 370.9,464 464,370.9 464,256 464,141.1 370.9,48 256,48 Z M 362.6,192.9 345,174.8 c -0.7,-0.8 -1.8,-1.2 -2.8,-1.2 -1.1,0 -2.1,0.4 -2.8,1.2 L 217.4,297.7 173,253.3 c -0.8,-0.8 -1.8,-1.2 -2.8,-1.2 -1,0 -2,0.4 -2.8,1.2 l -17.8,17.8 c -1.6,1.6 -1.6,4.1 0,5.7 l 56,56 c 3.6,3.6 8,5.7 11.7,5.7 5.3,0 9.9,-3.9 11.6,-5.5 H 229 L 362.7,198.6 c 1.4,-1.7 1.4,-4.2 -0.1,-5.7 z"></Path>
                         </Button>
                     </UniformGrid>
diff --git a/AIStudio.Wpf.Mind/Themes/MindNode.xaml b/AIStudio.Wpf.Mind/Themes/MindNode.xaml
index c11685d..bb2fd84 100644
--- a/AIStudio.Wpf.Mind/Themes/MindNode.xaml
+++ b/AIStudio.Wpf.Mind/Themes/MindNode.xaml
@@ -8,6 +8,7 @@
     <dd:DoubleToCornerRadius x:Key="DoubleToCornerRadius"/>
     <dd:IntToVisibilityConverter x:Key="IntToVisibilityConverter"/>
     <dd:DoubleToThickness x:Key="DoubleToThickness"/>
+    <dd:NullableToVisibilityConverter x:Key="NullableToVisibilityConverter"/>
 
     <!-- Toggle Button -->
     <Style x:Key="ExpandCollapseToggleStyle" TargetType="ToggleButton">
@@ -76,8 +77,8 @@
                                 <ColumnDefinition Width="Auto"/>
                                 <ColumnDefinition Width="Auto"/>
                             </Grid.ColumnDefinitions>
-                            <controls:RateControl Grid.Column="0" />
-                            <controls:PriorityControl Grid.Column="1" Width="20" Height="20" Priority="{Binding Priority}" Visibility="{Binding Priority,Converter={dd:ConverterValueSetToOppositeVisibility},ConverterParameter=0}"/>
+                            <controls:RateControl Grid.Column="0" Width="18" Height="18" Rate="{Binding Rate}" Visibility="{Binding Rate,Converter={StaticResource NullableToVisibilityConverter}}"/>
+                            <controls:PriorityControl Grid.Column="1" Width="18" Height="18" Priority="{Binding Priority}" Visibility="{Binding Priority,Converter={StaticResource NullableToVisibilityConverter}}"/>
                             <dd:TextControl Grid.Column="2" />
                             <controls:LinkControl Grid.Column="3"/>
                             <controls:RemarkControl Grid.Column="4"/>
diff --git a/AIStudio.Wpf.Mind/ViewModels/MindDiagramViewModel.cs b/AIStudio.Wpf.Mind/ViewModels/MindDiagramViewModel.cs
index d12b41f..0acb79c 100644
--- a/AIStudio.Wpf.Mind/ViewModels/MindDiagramViewModel.cs
+++ b/AIStudio.Wpf.Mind/ViewModels/MindDiagramViewModel.cs
@@ -659,6 +659,10 @@ namespace AIStudio.Wpf.Mind.ViewModels
             {
                 SelectedItems.OfType<MindNode>().ToList().ForEach(p => p.Priority = priority);
             }
+            else
+            {
+                SelectedItems.OfType<MindNode>().ToList().ForEach(p => p.Priority = null);
+            }
         }
 
         private void ExecuteAddRatioCommand(object obj)
diff --git a/AIStudio.Wpf.Mind/ViewModels/MindNode.cs b/AIStudio.Wpf.Mind/ViewModels/MindNode.cs
index bc9ca0a..c34c2c0 100644
--- a/AIStudio.Wpf.Mind/ViewModels/MindNode.cs
+++ b/AIStudio.Wpf.Mind/ViewModels/MindNode.cs
@@ -265,8 +265,8 @@ namespace AIStudio.Wpf.Mind.ViewModels
             }
         }
 
-        private double _priority;
-        public double Priority
+        private double? _priority;
+        public double? Priority
         {
             get
             {
@@ -278,8 +278,8 @@ namespace AIStudio.Wpf.Mind.ViewModels
             }
         }
 
-        private double _rate;
-        public double Rate
+        private double? _rate;
+        public double? Rate
         {
             get
             {
diff --git a/Directory.Build.Props b/Directory.Build.Props
index b3d0e9d..4d652c4 100644
--- a/Directory.Build.Props
+++ b/Directory.Build.Props
@@ -1,7 +1,7 @@
 <Project>
   <!-- Project properties -->
   <PropertyGroup>
-    <TargetFrameworks>net461;netcoreapp3.1;net5.0-windows</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.1;net5.0-windows</TargetFrameworks>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">