[Hosts]Indicate when an entry input field is invalid (#31407)

* [Hosts]Indicate when an entry input field is invalid

* Minor styling fix

* Update src/modules/Hosts/Hosts/Strings/en-us/Resources.resw

Co-authored-by: Davide Giacometti <davide.giacometti@outlook.it>

* Update src/modules/Hosts/Hosts/Strings/en-us/Resources.resw

Co-authored-by: Davide Giacometti <davide.giacometti@outlook.it>

* Change messages to "Has to be"

---------

Co-authored-by: Niels Laute <niels.laute@live.nl>
Co-authored-by: Davide Giacometti <davide.giacometti@outlook.it>

src/modules/Hosts/Hosts/HostsXAML/Views/MainPage.xaml

@@ -450,7 +450,23 @@
                     <TextBox
                         x:Uid="Address"
                         IsSpellCheckEnabled="False"
-                        Text="{Binding Address, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
+                        Text="{Binding Address, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
+                        <TextBox.Description>
+                            <StackPanel
+                                Margin="0,4"
+                                Orientation="Horizontal"
+                                Spacing="4"
+                                Visibility="{Binding IsAddressValid, Converter={StaticResource BoolToInvertedVisibilityConverter}}">
+                                <FontIcon
+                                    Margin="0,0,0,0"
+                                    AutomationProperties.AccessibilityView="Raw"
+                                    FontSize="14"
+                                    Foreground="{ThemeResource SystemFillColorCautionBrush}"
+                                    Glyph="&#xE7BA;" />
+                                <TextBlock x:Uid="EntryAddressIsInvalidWarning" />
+                            </StackPanel>
+                        </TextBox.Description>
+                    </TextBox>
                     <TextBox
                         x:Uid="Hosts"
                         AcceptsReturn="False"
@@ -459,7 +475,22 @@
                         ScrollViewer.VerticalScrollBarVisibility="Visible"
                         ScrollViewer.VerticalScrollMode="Enabled"
                         Text="{Binding Hosts, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
-                        TextWrapping="Wrap" />
+                        TextWrapping="Wrap">
+                        <TextBox.Description>
+                            <StackPanel
+                                Margin="0,4"
+                                Orientation="Horizontal"
+                                Spacing="4"
+                                Visibility="{Binding IsHostsValid, Converter={StaticResource BoolToInvertedVisibilityConverter}}">
+                                <FontIcon
+                                    AutomationProperties.AccessibilityView="Raw"
+                                    FontSize="14"
+                                    Foreground="{ThemeResource SystemFillColorCautionBrush}"
+                                    Glyph="&#xE7BA;" />
+                                <TextBlock x:Uid="EntryHostsIsInvalidWarning" />
+                            </StackPanel>
+                        </TextBox.Description>
+                    </TextBox>
                     <TextBox
                         x:Uid="Comment"
                         AcceptsReturn="False"

src/modules/Hosts/Hosts/Models/Entry.cs

@@ -16,6 +16,7 @@ namespace Hosts.Models
 
         [ObservableProperty]
         [NotifyPropertyChangedFor(nameof(Valid))]
+        [NotifyPropertyChangedFor(nameof(IsAddressValid))]
         private string _address;
 
         partial void OnAddressChanged(string value)
@@ -36,6 +37,7 @@ namespace Hosts.Models
 
         [ObservableProperty]
         [NotifyPropertyChangedFor(nameof(Valid))]
+        [NotifyPropertyChangedFor(nameof(IsHostsValid))]
         private string _hosts;
 
         partial void OnHostsChanged(string value)
@@ -61,6 +63,10 @@ namespace Hosts.Models
 
         public bool Valid => Validate(true);
 
+        public bool IsAddressValid => ValidateAddressField();
+
+        public bool IsHostsValid => ValidateHostsField(true);
+
         public string Line { get; private set; }
 
         public AddressType Type { get; private set; }
@@ -152,6 +158,16 @@ namespace Hosts.Models
             };
         }
 
+        private bool ValidateAddressField()
+        {
+            return Type != AddressType.Invalid;
+        }
+
+        private bool ValidateHostsField(bool validateHostsLength)
+        {
+            return ValidationHelper.ValidHosts(Hosts, validateHostsLength);
+        }
+
         public bool Validate(bool validateHostsLength)
         {
             if (Equals("102.54.94.97", "rhino.acme.com", "source server") || Equals("38.25.63.10", "x.acme.com", "x client host"))
@@ -159,7 +175,7 @@ namespace Hosts.Models
                 return false;
             }
 
-            return Type != AddressType.Invalid && ValidationHelper.ValidHosts(Hosts, validateHostsLength);
+            return ValidateAddressField() && ValidateHostsField(validateHostsLength);
         }
 
         private bool Equals(string address, string hosts, string comment)

src/modules/Hosts/Hosts/Strings/en-us/Resources.resw

@@ -299,6 +299,12 @@
     <value>Entries contain too many hosts</value>
     <comment>"Hosts" refers to the system hosts file, do not loc</comment>
   </data>
+  <data name="EntryAddressIsInvalidWarning.Text" xml:space="preserve">
+    <value>Has to be a valid IPv4 or IPv6 address</value>
+  </data>
+  <data name="EntryHostsIsInvalidWarning.Text" xml:space="preserve">
+    <value>Has to be one or more valid host names separated by spaces</value>
+  </data>
   <data name="UpdateBtn" xml:space="preserve">
     <value>Update</value>
   </data>