Set BorderBrush and Underline to ValidationErrorBrush in ComboBox

Author: duniubartek

MainDemo.Wpf/Domain/NotNullValidationRule.cs

@@ -0,0 +1,13 @@
+using System.Globalization;
+using System.Windows.Controls;
+
+namespace MaterialDesignDemo.Domain
+{
+    public class NotNullValidationRule : ValidationRule
+    {
+        public override ValidationResult Validate(object value, CultureInfo cultureInfo)
+        {
+            return value == null ? new ValidationResult(false, "Field is required.") : ValidationResult.ValidResult;
+        }
+    }
+}

MainDemo.Wpf/Domain/TextFieldsViewModel.cs

@@ -14,12 +14,14 @@ public class TextFieldsViewModel : INotifyPropertyChanged
     {
         private string _name;
         private int _selectedValueOne;
+        private int? _selectedValueTwo;
 
         public TextFieldsViewModel()
         {
             LongListToTestComboVirtualization = new List<int>(Enumerable.Range(0, 1000));
 
             SelectedValueOne = LongListToTestComboVirtualization.Skip(2).First();
+            SelectedValueTwo = null;
         }
 
         public string Name
@@ -40,6 +42,15 @@ public int SelectedValueOne
             }
         }
 
+        public int? SelectedValueTwo
+        {
+            get { return _selectedValueTwo; }
+            set
+            {
+                this.MutateVerbose(ref _selectedValueTwo, value, RaisePropertyChanged());
+            }
+        }
+
         public IList<int> LongListToTestComboVirtualization { get; }
 
         public DemoItem DemoItem => new DemoItem { Name = "Mr. Test"};

MainDemo.Wpf/MaterialDesignDemo.csproj

@@ -93,6 +93,7 @@
     <Compile Include="Domain\DemoItem.cs" />
     <Compile Include="Domain\DialogsViewModel.cs" />
     <Compile Include="Domain\ListFieldsViewModel.cs" />
+    <Compile Include="Domain\NotNullValidationRule.cs" />
     <Compile Include="Domain\Sample4Dialog.xaml.cs">
       <DependentUpon>Sample4Dialog.xaml</DependentUpon>
     </Compile>

MainDemo.Wpf/TextFields.xaml

@@ -130,6 +130,13 @@
                           VerticalAlignment="Bottom"                           
                           ItemsSource="{Binding LongListToTestComboVirtualization}"                          
                           SelectedValue="{Binding SelectedValueOne}">
+                    <ComboBox.SelectedItem>
+                        <Binding Path="SelectedValueOne" Mode="TwoWay" UpdateSourceTrigger="PropertyChanged">
+                            <Binding.ValidationRules>
+                                <domain1:NotNullValidationRule ValidatesOnTargetUpdated="True"/>
+                            </Binding.ValidationRules>
+                        </Binding>
+                    </ComboBox.SelectedItem>
                     <ComboBox.ItemsPanel>
                         <ItemsPanelTemplate>
                             <VirtualizingStackPanel />
@@ -142,6 +149,13 @@
                           VerticalAlignment="Bottom" 
                           IsEditable="True"                          
                           ItemsSource="{Binding LongListToTestComboVirtualization}">
+                    <ComboBox.SelectedItem>
+                        <Binding Path="SelectedValueTwo" Mode="TwoWay" UpdateSourceTrigger="PropertyChanged">
+                            <Binding.ValidationRules>
+                                <domain1:NotNullValidationRule ValidatesOnTargetUpdated="True"/>
+                            </Binding.ValidationRules>
+                        </Binding>
+                    </ComboBox.SelectedItem>
                     <ComboBox.ItemsPanel>
                         <ItemsPanelTemplate>
                             <VirtualizingStackPanel />

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.ComboBox.xaml

@@ -12,7 +12,7 @@
     <converters:TextFieldHintVisibilityConverter x:Key="TextFieldHintVisibilityConverter" IsNotEmptyValue="Collapsed" />
     <converters:MathConverter x:Key="MathAddConverter" Operation="Add" />
     <converters:BrushRoundConverter x:Key="BrushRoundConverter" />
-    
+
     <system:Double x:Key="PopupContentPresenterExtend">4</system:Double>
     <system:Double x:Key="PopupTopBottomMargin">8</system:Double>
     <system:Double x:Key="PopupLeftRightMargin">16</system:Double>
@@ -86,7 +86,7 @@
             </Grid>
         </Grid>
     </ControlTemplate>
-    
+
     <ControlTemplate x:Key="PopupContentDownTemplate" TargetType="ContentControl">
         <Grid MinWidth="{Binding ElementName=templateRoot, Path=ActualWidth, Converter={StaticResource MathAddConverter}, ConverterParameter=32}"
               Margin="6">
@@ -114,7 +114,7 @@
                         CornerRadius="2 2 0 0"
                         Background="{Binding ElementName=PART_Popup, Path=Background}"
                         Height="{StaticResource PopupTopBottomMargin}"/>
-                
+
                 <Grid Grid.Row="1">
                     <Grid.ColumnDefinitions>
                         <ColumnDefinition Width="Auto"/>
@@ -147,7 +147,7 @@
             </Grid>
         </Grid>
     </ControlTemplate>
-    
+
     <ControlTemplate x:Key="PopupContentDefaultTemplate" TargetType="ContentControl">
         <Grid MinWidth="{Binding ElementName=templateRoot, Path=ActualWidth, Converter={StaticResource MathAddConverter}, ConverterParameter=32}"
               Margin="6">
@@ -424,7 +424,7 @@
                                  IsReadOnly="{Binding IsReadOnly, RelativeSource={RelativeSource TemplatedParent}}"
                                  Style="{StaticResource MaterialDesignComboBoxEditableTextBox}"
                                  Visibility="Collapsed" />
-                        
+
                         <wpf:SmartHint x:Name="Hint"
                                        HintProxy="{Binding RelativeSource={RelativeSource TemplatedParent}, Converter={x:Static converters:HintProxyFabricConverter.Instance}}"
                                        FontSize="{TemplateBinding FontSize}"
@@ -520,6 +520,26 @@
             <Trigger Property="IsKeyboardFocused" Value="true">
                 <Setter TargetName="Underline" Property="IsActive" Value="True"/>
             </Trigger>
+            <Trigger Property="Validation.HasError" Value="true">
+                <Setter Property="BorderBrush" Value="{DynamicResource ValidationErrorBrush}"/>
+                <Setter TargetName="Underline" Property="Background" Value="{DynamicResource ValidationErrorBrush}"/>
+            </Trigger>
+            <MultiTrigger>
+                <MultiTrigger.Conditions>
+                    <Condition Property="IsMouseOver" Value="true" />
+                    <Condition Property="Validation.HasError" Value="true" />
+                </MultiTrigger.Conditions>
+                <Setter Property="BorderBrush" Value="{DynamicResource ValidationErrorBrush}"/>
+                <Setter TargetName="Underline" Property="Background" Value="{DynamicResource ValidationErrorBrush}"/>
+            </MultiTrigger>
+            <MultiTrigger>
+                <MultiTrigger.Conditions>
+                    <Condition Property="IsMouseOver" Value="true" />
+                    <Condition Property="Validation.HasError" Value="false" />
+                </MultiTrigger.Conditions>
+                <Setter Property="BorderBrush" Value="{DynamicResource PrimaryHueMidBrush}"/>
+                <Setter TargetName="Underline" Property="Background" Value="{DynamicResource PrimaryHueMidBrush}"/>
+            </MultiTrigger>
         </ControlTemplate.Triggers>
     </ControlTemplate>
 
@@ -543,9 +563,6 @@
         <Setter Property="Validation.ErrorTemplate" Value="{StaticResource MaterialDesignValidationErrorTemplate}"/>
         <Setter Property="Template" Value="{StaticResource MaterialDesignFloatingHintComboBoxTemplate}" />
         <Style.Triggers>
-            <Trigger Property="IsMouseOver" Value="true">
-                <Setter Property="BorderBrush" Value="{DynamicResource PrimaryHueMidBrush}" />
-            </Trigger>
             <Trigger Property="IsKeyboardFocused" Value="true">
                 <Setter Property="BorderBrush" Value="{DynamicResource PrimaryHueMidBrush}" />
             </Trigger>