Fixed: Migrate to FluentValidation 9

src/Lidarr.Api.V1/Artist/ArtistController.cs

@@ -78,7 +78,7 @@ namespace Lidarr.Api.V1.Artist
             Http.Validation.RuleBuilderExtensions.ValidId(SharedValidator.RuleFor(s => s.MetadataProfileId));
 
             SharedValidator.RuleFor(s => s.Path)
-                           .Cascade(CascadeMode.StopOnFirstFailure)
+                           .Cascade(CascadeMode.Stop)
                            .IsValidPath()
                            .SetValidator(rootFolderValidator)
                            .SetValidator(mappedNetworkDriveValidator)

src/Lidarr.Api.V1/Config/HostConfigController.cs

@@ -51,7 +51,7 @@ namespace Lidarr.Api.V1.Config
             SharedValidator.RuleFor(c => c.SslPort).NotEqual(c => c.Port).When(c => c.EnableSsl);
 
             SharedValidator.RuleFor(c => c.SslCertPath)
-                .Cascade(CascadeMode.StopOnFirstFailure)
+                .Cascade(CascadeMode.Stop)
                 .NotEmpty()
                 .IsValidPath()
                 .SetValidator(fileExistsValidator)

src/Lidarr.Api.V1/Lidarr.Api.V1.csproj

@@ -10,7 +10,7 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="System.Reflection.TypeExtensions" Version="4.7.0" />
-    <PackageReference Include="FluentValidation" Version="8.6.2" />
+    <PackageReference Include="FluentValidation" Version="9.5.4" />
     <PackageReference Include="Ical.Net" Version="4.2.0" />
     <PackageReference Include="NLog" Version="5.0.4" />
     <PackageReference Include="System.IO.Abstractions" Version="17.0.24" />

src/Lidarr.Api.V1/Profiles/Metadata/MetadataValidator.cs

@@ -31,76 +31,34 @@ namespace Lidarr.Api.V1.Profiles.Metadata
 
     public class PrimaryTypeValidator<T> : PropertyValidator
     {
-        public PrimaryTypeValidator()
-            : base("Must have at least one allowed primary type")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Must have at least one allowed primary type";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
-            var list = context.PropertyValue as IList<ProfilePrimaryAlbumTypeItemResource>;
-
-            if (list == null)
-            {
-                return false;
-            }
-
-            if (!list.Any(c => c.Allowed))
-            {
-                return false;
-            }
-
-            return true;
+            return context.PropertyValue is IList<ProfilePrimaryAlbumTypeItemResource> list &&
+                   list.Any(c => c.Allowed);
         }
     }
 
     public class SecondaryTypeValidator<T> : PropertyValidator
     {
-        public SecondaryTypeValidator()
-            : base("Must have at least one allowed secondary type")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Must have at least one allowed secondary type";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
-            var list = context.PropertyValue as IList<ProfileSecondaryAlbumTypeItemResource>;
-
-            if (list == null)
-            {
-                return false;
-            }
-
-            if (!list.Any(c => c.Allowed))
-            {
-                return false;
-            }
-
-            return true;
+            return context.PropertyValue is IList<ProfileSecondaryAlbumTypeItemResource> list &&
+                   list.Any(c => c.Allowed);
         }
     }
 
     public class ReleaseStatusValidator<T> : PropertyValidator
     {
-        public ReleaseStatusValidator()
-            : base("Must have at least one allowed release status")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Must have at least one allowed release status";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
-            var list = context.PropertyValue as IList<ProfileReleaseStatusItemResource>;
-
-            if (list == null)
-            {
-                return false;
-            }
-
-            if (!list.Any(c => c.Allowed))
-            {
-                return false;
-            }
-
-            return true;
+            return context.PropertyValue is IList<ProfileReleaseStatusItemResource> list &&
+                   list.Any(c => c.Allowed);
         }
     }
 }

src/Lidarr.Api.V1/Profiles/Quality/QualityCutoffValidator.cs

@@ -15,30 +15,17 @@ namespace Lidarr.Api.V1.Profiles.Quality
 
     public class ValidCutoffValidator<T> : PropertyValidator
     {
-        public ValidCutoffValidator()
-            : base("Cutoff must be an allowed quality or group")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Cutoff must be an allowed quality or group";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
-            int cutoff = (int)context.PropertyValue;
+            var cutoff = (int)context.PropertyValue;
             dynamic instance = context.ParentContext.InstanceToValidate;
             var items = instance.Items as IList<QualityProfileQualityItemResource>;
 
-            QualityProfileQualityItemResource cutoffItem = items.SingleOrDefault(i => (i.Quality == null && i.Id == cutoff) || i.Quality?.Id == cutoff);
-
-            if (cutoffItem == null)
-            {
-                return false;
-            }
-
-            if (!cutoffItem.Allowed)
-            {
-                return false;
-            }
+            var cutoffItem = items?.SingleOrDefault(i => (i.Quality == null && i.Id == cutoff) || i.Quality?.Id == cutoff);
 
-            return true;
+            return cutoffItem is { Allowed: true };
         }
     }
 }

src/Lidarr.Api.V1/Profiles/Quality/QualityItemsValidator.cs

@@ -23,139 +23,104 @@ namespace Lidarr.Api.V1.Profiles.Quality
 
     public class AllowedValidator<T> : PropertyValidator
     {
-        public AllowedValidator()
-            : base("Must contain at least one allowed quality")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Must contain at least one allowed quality";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
-            var list = context.PropertyValue as IList<QualityProfileQualityItemResource>;
-
-            if (list == null)
-            {
-                return false;
-            }
-
-            if (!list.Any(c => c.Allowed))
-            {
-                return false;
-            }
-
-            return true;
+            return context.PropertyValue is IList<QualityProfileQualityItemResource> list &&
+                   list.Any(c => c.Allowed);
         }
     }
 
     public class GroupItemValidator<T> : PropertyValidator
     {
-        public GroupItemValidator()
-            : base("Groups must contain multiple qualities")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Groups must contain multiple qualities";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
-            var items = context.PropertyValue as IList<QualityProfileQualityItemResource>;
-
-            if (items.Any(i => i.Name.IsNotNullOrWhiteSpace() && i.Items.Count <= 1))
+            if (context.PropertyValue is not IList<QualityProfileQualityItemResource> items)
             {
                 return false;
             }
 
-            return true;
+            return !items.Any(i => i.Name.IsNotNullOrWhiteSpace() && i.Items.Count <= 1);
         }
     }
 
     public class QualityNameValidator<T> : PropertyValidator
     {
-        public QualityNameValidator()
-            : base("Individual qualities should not be named")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Individual qualities should not be named";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
-            var items = context.PropertyValue as IList<QualityProfileQualityItemResource>;
-
-            if (items.Any(i => i.Name.IsNotNullOrWhiteSpace() && i.Quality != null))
+            if (context.PropertyValue is not IList<QualityProfileQualityItemResource> items)
             {
                 return false;
             }
 
-            return true;
+            return !items.Any(i => i.Name.IsNotNullOrWhiteSpace() && i.Quality != null);
         }
     }
 
     public class ItemGroupNameValidator<T> : PropertyValidator
     {
-        public ItemGroupNameValidator()
-            : base("Groups must have a name")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Groups must have a name";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
-            var items = context.PropertyValue as IList<QualityProfileQualityItemResource>;
-
-            if (items.Any(i => i.Quality == null && i.Name.IsNullOrWhiteSpace()))
+            if (context.PropertyValue is not IList<QualityProfileQualityItemResource> items)
             {
                 return false;
             }
 
-            return true;
+            return !items.Any(i => i.Quality == null && i.Name.IsNullOrWhiteSpace());
         }
     }
 
     public class ItemGroupIdValidator<T> : PropertyValidator
     {
-        public ItemGroupIdValidator()
-            : base("Groups must have an ID")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Groups must have an ID";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
-            var items = context.PropertyValue as IList<QualityProfileQualityItemResource>;
-
-            if (items.Any(i => i.Quality == null && i.Id == 0))
+            if (context.PropertyValue is not IList<QualityProfileQualityItemResource> items)
             {
                 return false;
             }
 
-            return true;
+            return !items.Any(i => i.Quality == null && i.Id == 0);
         }
     }
 
     public class UniqueIdValidator<T> : PropertyValidator
     {
-        public UniqueIdValidator()
-            : base("Groups must have a unique ID")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Groups must have a unique ID";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
-            var items = context.PropertyValue as IList<QualityProfileQualityItemResource>;
-
-            if (items.Where(i => i.Id > 0).Select(i => i.Id).GroupBy(i => i).Any(g => g.Count() > 1))
+            if (context.PropertyValue is not IList<QualityProfileQualityItemResource> items)
             {
                 return false;
             }
 
-            return true;
+            var ids = items.Where(i => i.Id > 0).Select(i => i.Id);
+            var groupedIds = ids.GroupBy(i => i);
+
+            return groupedIds.All(g => g.Count() == 1);
         }
     }
 
     public class UniqueQualityIdValidator<T> : PropertyValidator
     {
-        public UniqueQualityIdValidator()
-            : base("Qualities can only be used once")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Qualities can only be used once";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
-            var items = context.PropertyValue as IList<QualityProfileQualityItemResource>;
+            if (context.PropertyValue is not IList<QualityProfileQualityItemResource> items)
+            {
+                return false;
+            }
+
             var qualityIds = new HashSet<int>();
 
             foreach (var item in items)

src/Lidarr.Api.V1/RemotePathMappings/RemotePathMappingController.cs

@@ -28,7 +28,7 @@ namespace Lidarr.Api.V1.RemotePathMappings
                            .NotEmpty();
 
             SharedValidator.RuleFor(c => c.LocalPath)
-                           .Cascade(CascadeMode.StopOnFirstFailure)
+                           .Cascade(CascadeMode.Stop)
                            .IsValidPath()
                            .SetValidator(mappedNetworkDriveValidator)
                            .SetValidator(pathExistsValidator);

src/Lidarr.Api.V1/RootFolders/RootFolderController.cs

@@ -32,7 +32,7 @@ namespace Lidarr.Api.V1.RootFolders
             _rootFolderService = rootFolderService;
 
             SharedValidator.RuleFor(c => c.Path)
-                .Cascade(CascadeMode.StopOnFirstFailure)
+                .Cascade(CascadeMode.Stop)
                 .IsValidPath()
                 .SetValidator(mappedNetworkDriveValidator)
                 .SetValidator(startupFolderValidator)

src/Lidarr.Http/Lidarr.Http.csproj

@@ -3,7 +3,7 @@
     <TargetFrameworks>net6.0</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="FluentValidation" Version="8.6.2" />
+    <PackageReference Include="FluentValidation" Version="9.5.4" />
     <PackageReference Include="ImpromptuInterface" Version="7.0.1" />
     <PackageReference Include="NLog" Version="5.0.4" />
   </ItemGroup>

src/Lidarr.Http/REST/ResourceValidator.cs

@@ -4,7 +4,6 @@ using System.Linq;
 using System.Linq.Expressions;
 using FluentValidation;
 using FluentValidation.Internal;
-using FluentValidation.Resources;
 using Lidarr.Http.ClientSchema;
 
 namespace Lidarr.Http.REST
@@ -15,7 +14,7 @@ namespace Lidarr.Http.REST
         {
             var rule = new PropertyRule(fieldListAccessor.GetMember(), c => GetValue(c, fieldListAccessor.Compile(), fieldName), null, () => CascadeMode.Continue, typeof(TProperty), typeof(TResource));
             rule.PropertyName = fieldName;
-            rule.DisplayName = new StaticStringSource(fieldName);
+            rule.SetDisplayName(fieldName);
 
             AddRule(rule);
             return new RuleBuilder<TResource, TProperty>(rule, this);
@@ -25,12 +24,7 @@ namespace Lidarr.Http.REST
         {
             var resource = fieldListAccessor((TResource)container).SingleOrDefault(c => c.Name == fieldName);
 
-            if (resource == null)
-            {
-                return null;
-            }
-
-            return resource.Value;
+            return resource?.Value;
         }
     }
 }

src/Lidarr.Http/Validation/EmptyCollectionValidator.cs

@@ -6,10 +6,7 @@ namespace Lidarr.Http.Validation
 {
     public class EmptyCollectionValidator<T> : PropertyValidator
     {
-        public EmptyCollectionValidator()
-            : base("Collection Must Be Empty")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Collection Must Be Empty";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {

src/Lidarr.Http/Validation/RssSyncIntervalValidator.cs

@@ -4,10 +4,7 @@ namespace Lidarr.Http.Validation
 {
     public class RssSyncIntervalValidator : PropertyValidator
     {
-        public RssSyncIntervalValidator()
-            : base("Must be between 10 and 120 or 0 to disable")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Must be between 10 and 120 or 0 to disable";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
@@ -23,12 +20,7 @@ namespace Lidarr.Http.Validation
                 return true;
             }
 
-            if (value >= 10 && value <= 120)
-            {
-                return true;
-            }
-
-            return false;
+            return value is >= 10 and <= 120;
         }
     }
 }

src/NzbDrone.Common/Extensions/UrlExtensions.cs

@@ -16,18 +16,7 @@ namespace NzbDrone.Common.Extensions
                 return false;
             }
 
-            Uri uri;
-            if (!Uri.TryCreate(path, UriKind.Absolute, out uri))
-            {
-                return false;
-            }
-
-            if (!uri.IsWellFormedOriginalString())
-            {
-                return false;
-            }
-
-            return true;
+            return Uri.TryCreate(path, UriKind.Absolute, out var uri) && uri.IsWellFormedOriginalString();
         }
     }
 }

src/NzbDrone.Core.Test/NotificationTests/EmailTests/EmailSettingsValidatorFixture.cs

@@ -40,7 +40,6 @@ namespace NzbDrone.Core.Test.NotificationTests.EmailTests
         public void should_not_be_valid_if_port_is_out_of_range()
         {
             _emailSettings.Port = 900000;
-
             _validator.Validate(_emailSettings).IsValid.Should().BeFalse();
         }
 
@@ -48,7 +47,6 @@ namespace NzbDrone.Core.Test.NotificationTests.EmailTests
         public void should_not_be_valid_if_server_is_empty()
         {
             _emailSettings.Server = "";
-
             _validator.Validate(_emailSettings).IsValid.Should().BeFalse();
         }
 
@@ -61,7 +59,6 @@ namespace NzbDrone.Core.Test.NotificationTests.EmailTests
         }
 
         [TestCase("lidarr")]
-        [TestCase("lidarr@lidarr")]
         [TestCase("lidarr.audio")]
         public void should_not_be_valid_if_to_is_invalid(string email)
         {
@@ -71,7 +68,6 @@ namespace NzbDrone.Core.Test.NotificationTests.EmailTests
         }
 
         [TestCase("lidarr")]
-        [TestCase("lidarr@lidarr")]
         [TestCase("lidarr.audio")]
         public void should_not_be_valid_if_cc_is_invalid(string email)
         {
@@ -81,7 +77,6 @@ namespace NzbDrone.Core.Test.NotificationTests.EmailTests
         }
 
         [TestCase("lidarr")]
-        [TestCase("lidarr@lidarr")]
         [TestCase("lidarr.audio")]
         public void should_not_be_valid_if_bcc_is_invalid(string email)
         {

src/NzbDrone.Core/Download/Clients/rTorrent/RTorrentDirectoryValidator.cs

@@ -17,13 +17,13 @@ namespace NzbDrone.Core.Download.Clients.rTorrent
                                           PathExistsValidator pathExistsValidator,
                                           MappedNetworkDriveValidator mappedNetworkDriveValidator)
         {
-            RuleFor(c => c.MusicDirectory).Cascade(CascadeMode.StopOnFirstFailure)
-                                       .IsValidPath()
-                                       .SetValidator(rootFolderValidator)
-                                       .SetValidator(mappedNetworkDriveValidator)
-                                       .SetValidator(pathExistsValidator)
-                                       .When(c => c.MusicDirectory.IsNotNullOrWhiteSpace())
-                                       .When(c => c.Host == "localhost" || c.Host == "127.0.0.1");
+            RuleFor(c => c.MusicDirectory).Cascade(CascadeMode.Stop)
+                .IsValidPath()
+                .SetValidator(rootFolderValidator)
+                .SetValidator(mappedNetworkDriveValidator)
+                .SetValidator(pathExistsValidator)
+                .When(c => c.MusicDirectory.IsNotNullOrWhiteSpace())
+                .When(c => c.Host == "localhost" || c.Host == "127.0.0.1");
         }
     }
 }

src/NzbDrone.Core/ImportLists/Exclusions/ImportListExclusionExistsValidator.cs

@@ -7,11 +7,12 @@ namespace NzbDrone.Core.ImportLists.Exclusions
         private readonly IImportListExclusionService _importListExclusionService;
 
         public ImportListExclusionExistsValidator(IImportListExclusionService importListExclusionService)
-            : base("This exclusion has already been added.")
         {
             _importListExclusionService = importListExclusionService;
         }
 
+        protected override string GetDefaultMessageTemplate() => "This exclusion has already been added.";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)

src/NzbDrone.Core/Lidarr.Core.csproj

@@ -12,7 +12,7 @@
     <PackageReference Include="Servarr.FluentMigrator.Runner" Version="3.3.2.9" />
     <PackageReference Include="Servarr.FluentMigrator.Runner.SQLite" Version="3.3.2.9" />
     <PackageReference Include="Servarr.FluentMigrator.Runner.Postgres" Version="3.3.2.9" />
-    <PackageReference Include="FluentValidation" Version="8.6.2" />
+    <PackageReference Include="FluentValidation" Version="9.5.4" />
     <PackageReference Include="MailKit" Version="2.15.0" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.2" />
     <PackageReference Include="NLog" Version="5.0.4" />

src/NzbDrone.Core/Music/Utilities/AddArtistValidator.cs

@@ -19,7 +19,7 @@ namespace NzbDrone.Core.Music
                                   QualityProfileExistsValidator qualityProfileExistsValidator,
                                   MetadataProfileExistsValidator metadataProfileExistsValidator)
         {
-            RuleFor(c => c.Path).Cascade(CascadeMode.StopOnFirstFailure)
+            RuleFor(c => c.Path).Cascade(CascadeMode.Stop)
                                 .IsValidPath()
                                 .SetValidator(rootFolderValidator)
                                 .SetValidator(recycleBinValidator)

src/NzbDrone.Core/Organizer/FileNameValidation.cs

@@ -41,53 +41,36 @@ namespace NzbDrone.Core.Organizer
 
     public class ValidStandardTrackFormatValidator : PropertyValidator
     {
-        public ValidStandardTrackFormatValidator()
-            : base("Must contain Track Title and Track numbers OR Original Title")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Must contain Track Title and Track numbers OR Original Title";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
-            var value = context.PropertyValue as string;
-
-            if (!(FileNameBuilder.TrackTitleRegex.IsMatch(value) &&
-                FileNameBuilder.TrackRegex.IsMatch(value)) &&
-                !FileNameValidation.OriginalTokenRegex.IsMatch(value))
+            if (context.PropertyValue is not string value)
             {
                 return false;
             }
 
-            return true;
+            return (FileNameBuilder.TrackTitleRegex.IsMatch(value) && FileNameBuilder.TrackRegex.IsMatch(value)) ||
+                   FileNameValidation.OriginalTokenRegex.IsMatch(value);
         }
     }
 
     public class IllegalCharactersValidator : PropertyValidator
     {
-        private readonly char[] _invalidPathChars = Path.GetInvalidPathChars();
+        private static readonly char[] InvalidPathChars = Path.GetInvalidPathChars();
 
-        public IllegalCharactersValidator()
-            : base("Contains illegal characters: {InvalidCharacters}")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Contains illegal characters: {InvalidCharacters}";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {
             var value = context.PropertyValue as string;
-            var invalidCharacters = new List<char>();
 
             if (value.IsNullOrWhiteSpace())
             {
                 return true;
             }
 
-            foreach (var i in _invalidPathChars)
-            {
-                if (value.IndexOf(i) >= 0)
-                {
-                    invalidCharacters.Add(i);
-                }
-            }
-
+            var invalidCharacters = InvalidPathChars.Where(i => value!.IndexOf(i) >= 0).ToList();
             if (invalidCharacters.Any())
             {
                 context.MessageFormatter.AppendArgument("InvalidCharacters", string.Join("", invalidCharacters));

src/NzbDrone.Core/Profiles/Delay/DelayProfileTagInUseValidator.cs

@@ -10,11 +10,12 @@ namespace NzbDrone.Core.Profiles.Delay
         private readonly IDelayProfileService _delayProfileService;
 
         public DelayProfileTagInUseValidator(IDelayProfileService delayProfileService)
-            : base("One or more tags is used in another profile")
         {
             _delayProfileService = delayProfileService;
         }
 
+        protected override string GetDefaultMessageTemplate() => "One or more tags is used in another profile";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)
@@ -25,9 +26,7 @@ namespace NzbDrone.Core.Profiles.Delay
             dynamic instance = context.ParentContext.InstanceToValidate;
             var instanceId = (int)instance.Id;
 
-            var collection = context.PropertyValue as HashSet<int>;
-
-            if (collection == null || collection.Empty())
+            if (context.PropertyValue is not HashSet<int> collection || collection.Empty())
             {
                 return true;
             }

src/NzbDrone.Core/Validation/FileChmodValidator.cs

@@ -8,11 +8,12 @@ namespace NzbDrone.Core.Validation
         private readonly IDiskProvider _diskProvider;
 
         public FolderChmodValidator(IDiskProvider diskProvider)
-            : base("Must contain a valid Unix permissions octal")
         {
             _diskProvider = diskProvider;
         }
 
+        protected override string GetDefaultMessageTemplate() => "Must contain a valid Unix permissions octal";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)

src/NzbDrone.Core/Validation/FolderValidator.cs

@@ -5,10 +5,7 @@ namespace NzbDrone.Core.Validation
 {
     public class FolderValidator : PropertyValidator
     {
-        public FolderValidator()
-            : base("Invalid Path")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Invalid Path";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {

src/NzbDrone.Core/Validation/GuidValidator.cs

@@ -5,10 +5,7 @@ namespace NzbDrone.Core.Validation
 {
     public class GuidValidator : PropertyValidator
     {
-        public GuidValidator()
-            : base("String is not a valid Guid")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "String is not a valid Guid";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {

src/NzbDrone.Core/Validation/MetadataProfileExistsValidator.cs

@@ -8,11 +8,12 @@ namespace NzbDrone.Core.Validation
         private readonly IMetadataProfileService _profileService;
 
         public MetadataProfileExistsValidator(IMetadataProfileService profileService)
-            : base("Metadata profile does not exist")
         {
             _profileService = profileService;
         }
 
+        protected override string GetDefaultMessageTemplate() => "Metadata profile does not exist";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)

src/NzbDrone.Core/Validation/Paths/ArtistAncestorValidator.cs

@@ -10,11 +10,12 @@ namespace NzbDrone.Core.Validation.Paths
         private readonly IArtistService _artistService;
 
         public ArtistAncestorValidator(IArtistService artistService)
-            : base("Path is an ancestor of an existing artist")
         {
             _artistService = artistService;
         }
 
+        protected override string GetDefaultMessageTemplate() => "Path is an ancestor of an existing artist";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)

src/NzbDrone.Core/Validation/Paths/ArtistExistsValidator.cs

@@ -8,11 +8,12 @@ namespace NzbDrone.Core.Validation.Paths
         private readonly IArtistService _artistService;
 
         public ArtistExistsValidator(IArtistService artistService)
-            : base("This artist has already been added.")
         {
             _artistService = artistService;
         }
 
+        protected override string GetDefaultMessageTemplate() => "This artist has already been added.";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)

src/NzbDrone.Core/Validation/Paths/ArtistPathValidator.cs

@@ -10,11 +10,12 @@ namespace NzbDrone.Core.Validation.Paths
         private readonly IArtistService _artistService;
 
         public ArtistPathValidator(IArtistService artistService)
-            : base("Path is already configured for an existing artist")
         {
             _artistService = artistService;
         }
 
+        protected override string GetDefaultMessageTemplate() => "Path is already configured for an existing artist";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)

src/NzbDrone.Core/Validation/Paths/FileExistsValidator.cs

@@ -8,11 +8,12 @@ namespace NzbDrone.Core.Validation.Paths
         private readonly IDiskProvider _diskProvider;
 
         public FileExistsValidator(IDiskProvider diskProvider)
-            : base("File does not exist")
         {
             _diskProvider = diskProvider;
         }
 
+        protected override string GetDefaultMessageTemplate() => "File does not exist";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)

src/NzbDrone.Core/Validation/Paths/FolderWritableValidator.cs

@@ -9,11 +9,12 @@ namespace NzbDrone.Core.Validation.Paths
         private readonly IDiskProvider _diskProvider;
 
         public FolderWritableValidator(IDiskProvider diskProvider)
-            : base($"Folder is not writable by user {Environment.UserName}")
         {
             _diskProvider = diskProvider;
         }
 
+        protected override string GetDefaultMessageTemplate() => $"Folder is not writable by user {Environment.UserName}";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)

src/NzbDrone.Core/Validation/Paths/MappedNetworkDriveValidator.cs

@@ -14,12 +14,13 @@ namespace NzbDrone.Core.Validation.Paths
         private static readonly Regex DriveRegex = new Regex(@"[a-z]\:\\", RegexOptions.Compiled | RegexOptions.IgnoreCase);
 
         public MappedNetworkDriveValidator(IRuntimeInfo runtimeInfo, IDiskProvider diskProvider)
-            : base("Mapped Network Drive and Windows Service")
         {
             _runtimeInfo = runtimeInfo;
             _diskProvider = diskProvider;
         }
 
+        protected override string GetDefaultMessageTemplate() => "Mapped Network Drive and Windows Service";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)
@@ -46,12 +47,7 @@ namespace NzbDrone.Core.Validation.Paths
 
             var mount = _diskProvider.GetMount(path);
 
-            if (mount != null && mount.DriveType == DriveType.Network)
-            {
-                return false;
-            }
-
-            return true;
+            return mount is not { DriveType: DriveType.Network };
         }
     }
 }

src/NzbDrone.Core/Validation/Paths/PathExistsValidator.cs

@@ -8,11 +8,12 @@ namespace NzbDrone.Core.Validation.Paths
         private readonly IDiskProvider _diskProvider;
 
         public PathExistsValidator(IDiskProvider diskProvider)
-            : base("Path does not exist")
         {
             _diskProvider = diskProvider;
         }
 
+        protected override string GetDefaultMessageTemplate() => "Path does not exist";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)

src/NzbDrone.Core/Validation/Paths/PathValidator.cs

@@ -14,10 +14,7 @@ namespace NzbDrone.Core.Validation.Paths
 
     public class PathValidator : PropertyValidator
     {
-        public PathValidator()
-            : base("Invalid Path")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Invalid Path";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {

src/NzbDrone.Core/Validation/Paths/RecycleBinValidator.cs

@@ -9,11 +9,12 @@ namespace NzbDrone.Core.Validation.Paths
         private readonly IConfigService _configService;
 
         public RecycleBinValidator(IConfigService configService)
-            : base("Path is {relationship} configured recycle bin folder")
         {
             _configService = configService;
         }
 
+        protected override string GetDefaultMessageTemplate() => "Path is {relationship} configured recycle bin folder";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             var recycleBin = _configService.RecycleBin;

src/NzbDrone.Core/Validation/Paths/RootFolderAncestorValidator.cs

@@ -10,11 +10,12 @@ namespace NzbDrone.Core.Validation.Paths
         private readonly IRootFolderService _rootFolderService;
 
         public RootFolderAncestorValidator(IRootFolderService rootFolderService)
-            : base("Path is an ancestor of an existing root folder")
         {
             _rootFolderService = rootFolderService;
         }
 
+        protected override string GetDefaultMessageTemplate() => "Path is an ancestor of an existing root folder";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)

src/NzbDrone.Core/Validation/Paths/RootFolderValidator.cs

@@ -9,11 +9,12 @@ namespace NzbDrone.Core.Validation.Paths
         private readonly IRootFolderService _rootFolderService;
 
         public RootFolderValidator(IRootFolderService rootFolderService)
-            : base("Path is already configured as a root folder")
         {
             _rootFolderService = rootFolderService;
         }
 
+        protected override string GetDefaultMessageTemplate() => "Path is already configured as a root folder";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)

src/NzbDrone.Core/Validation/Paths/StartupFolderValidator.cs

@@ -9,11 +9,12 @@ namespace NzbDrone.Core.Validation.Paths
         private readonly IAppFolderInfo _appFolderInfo;
 
         public StartupFolderValidator(IAppFolderInfo appFolderInfo)
-            : base("Path cannot be {relationship} the start up folder")
         {
             _appFolderInfo = appFolderInfo;
         }
 
+        protected override string GetDefaultMessageTemplate() => "Path cannot be {relationship} the start up folder";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)

src/NzbDrone.Core/Validation/Paths/SystemFolderValidator.cs

@@ -6,10 +6,7 @@ namespace NzbDrone.Core.Validation.Paths
 {
     public class SystemFolderValidator : PropertyValidator
     {
-        public SystemFolderValidator()
-            : base("Is {relationship} system folder {systemFolder}")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Is {relationship} system folder {systemFolder}";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {

src/NzbDrone.Core/Validation/QualityProfileExistsValidator.cs

@@ -8,11 +8,12 @@ namespace NzbDrone.Core.Validation
         private readonly IQualityProfileService _profileService;
 
         public QualityProfileExistsValidator(IQualityProfileService profileService)
-            : base("Quality Profile does not exist")
         {
             _profileService = profileService;
         }
 
+        protected override string GetDefaultMessageTemplate() => "Quality Profile does not exist";
+
         protected override bool IsValid(PropertyValidatorContext context)
         {
             if (context.PropertyValue == null)

src/NzbDrone.Core/Validation/UrlValidator.cs

@@ -14,10 +14,7 @@ namespace NzbDrone.Core.Validation
 
     public class UrlValidator : PropertyValidator
     {
-        public UrlValidator()
-            : base("Invalid Url")
-        {
-        }
+        protected override string GetDefaultMessageTemplate() => "Invalid Url";
 
         protected override bool IsValid(PropertyValidatorContext context)
         {

src/NzbDrone.Test.Common/Lidarr.Test.Common.csproj

@@ -4,7 +4,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="FluentAssertions" Version="5.10.3" />
-    <PackageReference Include="FluentValidation" Version="8.6.2" />
+    <PackageReference Include="FluentValidation" Version="9.5.4" />
     <PackageReference Include="Moq" Version="4.16.1" />
     <PackageReference Include="NLog" Version="5.0.4" />
     <PackageReference Include="NUnit" Version="3.13.3" />