diff --git a/BallanceTasEditor/BallanceTasEditor/BallanceTasEditor.csproj b/BallanceTasEditor/BallanceTasEditor/BallanceTasEditor.csproj
index efcd7cb..53f668b 100644
--- a/BallanceTasEditor/BallanceTasEditor/BallanceTasEditor.csproj
+++ b/BallanceTasEditor/BallanceTasEditor/BallanceTasEditor.csproj
@@ -17,7 +17,7 @@
     <PackageReference Include="CommunityToolkit.HighPerformance" Version="8.4.0" />
     <PackageReference Include="CommunityToolkit.Mvvm" Version="8.2.1" />
     <PackageReference Include="DotNetZip" Version="1.9.1.8" />
-    <PackageReference Include="LanguageExt.Core" Version="4.4.9" />
+    <PackageReference Include="OneOf" Version="3.0.271" />
     <PackageReference Include="System.Configuration.ConfigurationManager" Version="10.0.5" />
   </ItemGroup>
 
diff --git a/BallanceTasEditor/BallanceTasEditor/Frontend/Validator/ValidatorAdapter.cs b/BallanceTasEditor/BallanceTasEditor/Frontend/Validator/ValidatorAdapter.cs
index 555f1c0..98ae9d6 100644
--- a/BallanceTasEditor/BallanceTasEditor/Frontend/Validator/ValidatorAdapter.cs
+++ b/BallanceTasEditor/BallanceTasEditor/Frontend/Validator/ValidatorAdapter.cs
@@ -17,20 +17,16 @@ namespace BallanceTasEditor.Frontend.Validator {
         private readonly IValidator<TIn, TOut> m_Validator;
 
         public ValidationResult? Validate(TIn value, ValidationContext validationContext) {
-            // YYC MARK:
-            // Due to the shitty behavior of LanguageExt
-            // which do not allow I return nullable class from Match,
-            // I was forcely use MatchUnsafe.
-            return m_Validator.Validate(value).MatchUnsafe(
-                Left: v => ValidationResult.Success,
-                Right: err => new ValidationResult(err)
+            return m_Validator.Validate(value).Match(
+                v => ValidationResult.Success,
+                err => new ValidationResult(err)
             );
         }
 
         public TOut Conclude(TIn value) {
             return m_Validator.Validate(value).Match(
-                Left: v => v,
-                Right: _ => throw new InvalidOperationException("Can not unwrap an error casting.")
+                v => v,
+                _ => throw new InvalidOperationException("Can not unwrap an error casting.")
             );
         }
 
diff --git a/BallanceTasEditor/BallanceTasEditor/Frontend/Validator/Validators.cs b/BallanceTasEditor/BallanceTasEditor/Frontend/Validator/Validators.cs
index deb387e..4e59ef4 100644
--- a/BallanceTasEditor/BallanceTasEditor/Frontend/Validator/Validators.cs
+++ b/BallanceTasEditor/BallanceTasEditor/Frontend/Validator/Validators.cs
@@ -1,4 +1,4 @@
-using LanguageExt;
+using OneOf;
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -8,11 +8,11 @@ using System.Threading.Tasks;
 namespace BallanceTasEditor.Frontend.Validator {
 
     public interface IValidator<TIn, TOut> {
-         Either<TOut, string> Validate(TIn value);
+         OneOf<TOut, string> Validate(TIn value);
     }
 
     public sealed class FpsValidator : IValidator<string, uint> {
-        public Either<uint, string> Validate(string value) {
+        public OneOf<uint, string> Validate(string value) {
             if (uint.TryParse(value, System.Globalization.CultureInfo.InvariantCulture, out uint fps)) {
                 if (Backend.FpsConverter.IsValidFps(fps)) {
                     return fps;
@@ -26,7 +26,7 @@ namespace BallanceTasEditor.Frontend.Validator {
     }
 
     public sealed class CountValidator : IValidator<string, int> {
-        public Either<int, string> Validate(string value) {
+        public OneOf<int, string> Validate(string value) {
             if (int.TryParse(value, System.Globalization.CultureInfo.InvariantCulture, out int count)) {
                 if (count > 0) {
                     return count;