diff --git a/src/UniTask.NetCore/Linq/AsyncEnumeratorBase.cs b/src/UniTask.NetCore/Linq/AsyncEnumeratorBase.cs
index b4b4493..3f3ba2f 100644
--- a/src/UniTask.NetCore/Linq/AsyncEnumeratorBase.cs
+++ b/src/UniTask.NetCore/Linq/AsyncEnumeratorBase.cs
@@ -212,7 +212,7 @@ namespace Cysharp.Threading.Tasks.Linq
         protected abstract bool TrySetCurrentCore(TAwait awaitResult, out bool terminateIteration);
 
         // Util
-        protected TSource SourceCurrent => enumerator.Current;
+        protected TSource SourceCurrent { get; private set; }
 
         protected (bool waitCallback, bool requireNextIteration) ActionCompleted(bool trySetCurrentResult, out bool moveNextResult)
         {
@@ -287,7 +287,8 @@ namespace Cysharp.Threading.Tasks.Linq
         {
             if (sourceHasCurrent)
             {
-                var task = TransformAsync(enumerator.Current);
+                SourceCurrent = enumerator.Current;
+                var task = TransformAsync(SourceCurrent);
                 if (UnwarapTask(task, out var taskResult))
                 {
                     var currentResult = TrySetCurrentCore(taskResult, out var terminateIteration);
diff --git a/src/UniTask.NetCore/Linq/Distinct.cs b/src/UniTask.NetCore/Linq/Distinct.cs
index fc4aa48..2868fcd 100644
--- a/src/UniTask.NetCore/Linq/Distinct.cs
+++ b/src/UniTask.NetCore/Linq/Distinct.cs
@@ -9,8 +9,6 @@ namespace Cysharp.Threading.Tasks.Linq
     {
         public static IUniTaskAsyncEnumerable<TSource> Distinct<TSource>(this IUniTaskAsyncEnumerable<TSource> source)
         {
-            Error.ThrowArgumentNullException(source, nameof(source));
-
             return Distinct(source, EqualityComparer<TSource>.Default);
         }
 
@@ -21,6 +19,48 @@ namespace Cysharp.Threading.Tasks.Linq
 
             return new Distinct<TSource>(source, comparer);
         }
+
+        public static IUniTaskAsyncEnumerable<TSource> Distinct<TSource, TKey>(this IUniTaskAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector)
+        {
+            return Distinct(source, keySelector, EqualityComparer<TKey>.Default);
+        }
+
+        public static IUniTaskAsyncEnumerable<TSource> Distinct<TSource, TKey>(this IUniTaskAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            Error.ThrowArgumentNullException(source, nameof(source));
+            Error.ThrowArgumentNullException(keySelector, nameof(keySelector));
+            Error.ThrowArgumentNullException(comparer, nameof(comparer));
+
+            return new Distinct<TSource, TKey>(source, keySelector, comparer);
+        }
+
+        public static IUniTaskAsyncEnumerable<TSource> DistinctAwait<TSource, TKey>(this IUniTaskAsyncEnumerable<TSource> source, Func<TSource, UniTask<TKey>> keySelector)
+        {
+            return DistinctAwait(source, keySelector, EqualityComparer<TKey>.Default);
+        }
+
+        public static IUniTaskAsyncEnumerable<TSource> DistinctAwait<TSource, TKey>(this IUniTaskAsyncEnumerable<TSource> source, Func<TSource, UniTask<TKey>> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            Error.ThrowArgumentNullException(source, nameof(source));
+            Error.ThrowArgumentNullException(keySelector, nameof(keySelector));
+            Error.ThrowArgumentNullException(comparer, nameof(comparer));
+
+            return new DistinctAwait<TSource, TKey>(source, keySelector, comparer);
+        }
+
+        public static IUniTaskAsyncEnumerable<TSource> DistinctAwaitWithCancellation<TSource, TKey>(this IUniTaskAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, UniTask<TKey>> keySelector)
+        {
+            return DistinctAwaitWithCancellation(source, keySelector, EqualityComparer<TKey>.Default);
+        }
+
+        public static IUniTaskAsyncEnumerable<TSource> DistinctAwaitWithCancellation<TSource, TKey>(this IUniTaskAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, UniTask<TKey>> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            Error.ThrowArgumentNullException(source, nameof(source));
+            Error.ThrowArgumentNullException(keySelector, nameof(keySelector));
+            Error.ThrowArgumentNullException(comparer, nameof(comparer));
+
+            return new DistinctAwaitCancellation<TSource, TKey>(source, keySelector, comparer);
+        }
     }
 
     internal sealed class Distinct<TSource> : IUniTaskAsyncEnumerable<TSource>
@@ -73,4 +113,165 @@ namespace Cysharp.Threading.Tasks.Linq
             }
         }
     }
+
+    internal sealed class Distinct<TSource, TKey> : IUniTaskAsyncEnumerable<TSource>
+    {
+        readonly IUniTaskAsyncEnumerable<TSource> source;
+        readonly Func<TSource, TKey> keySelector;
+        readonly IEqualityComparer<TKey> comparer;
+
+        public Distinct(IUniTaskAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            this.source = source;
+            this.keySelector = keySelector;
+            this.comparer = comparer;
+        }
+
+        public IUniTaskAsyncEnumerator<TSource> GetAsyncEnumerator(CancellationToken cancellationToken = default)
+        {
+            return new Enumerator(source, keySelector, comparer, cancellationToken);
+        }
+
+        class Enumerator : AsyncEnumeratorBase<TSource, TSource>
+        {
+            readonly HashSet<TKey> set;
+            readonly Func<TSource, TKey> keySelector;
+
+            public Enumerator(IUniTaskAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
+
+                : base(source, cancellationToken)
+            {
+                this.set = new HashSet<TKey>(comparer);
+                this.keySelector = keySelector;
+            }
+
+            protected override bool TryMoveNextCore(bool sourceHasCurrent, out bool result)
+            {
+                if (sourceHasCurrent)
+                {
+                    var v = SourceCurrent;
+                    if (set.Add(keySelector(v)))
+                    {
+                        Current = v;
+                        result = true;
+                        return true;
+                    }
+                    else
+                    {
+                        result = default;
+                        return false;
+                    }
+                }
+
+                result = false;
+                return true;
+            }
+        }
+    }
+
+    internal sealed class DistinctAwait<TSource, TKey> : IUniTaskAsyncEnumerable<TSource>
+    {
+        readonly IUniTaskAsyncEnumerable<TSource> source;
+        readonly Func<TSource, UniTask<TKey>> keySelector;
+        readonly IEqualityComparer<TKey> comparer;
+
+        public DistinctAwait(IUniTaskAsyncEnumerable<TSource> source, Func<TSource, UniTask<TKey>> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            this.source = source;
+            this.keySelector = keySelector;
+            this.comparer = comparer;
+        }
+
+        public IUniTaskAsyncEnumerator<TSource> GetAsyncEnumerator(CancellationToken cancellationToken = default)
+        {
+            return new Enumerator(source, keySelector, comparer, cancellationToken);
+        }
+
+        class Enumerator : AsyncEnumeratorAwaitSelectorBase<TSource, TSource, TKey>
+        {
+            readonly HashSet<TKey> set;
+            readonly Func<TSource, UniTask<TKey>> keySelector;
+
+            public Enumerator(IUniTaskAsyncEnumerable<TSource> source, Func<TSource, UniTask<TKey>> keySelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
+
+                : base(source, cancellationToken)
+            {
+                this.set = new HashSet<TKey>(comparer);
+                this.keySelector = keySelector;
+            }
+
+            protected override UniTask<TKey> TransformAsync(TSource sourceCurrent)
+            {
+                return keySelector(sourceCurrent);
+            }
+
+            protected override bool TrySetCurrentCore(TKey awaitResult, out bool terminateIteration)
+            {
+                if (set.Add(awaitResult))
+                {
+                    Current = SourceCurrent;
+                    terminateIteration = false;
+                    return true;
+                }
+                else
+                {
+                    terminateIteration = false;
+                    return false;
+                }
+            }
+        }
+    }
+
+    internal sealed class DistinctAwaitCancellation<TSource, TKey> : IUniTaskAsyncEnumerable<TSource>
+    {
+        readonly IUniTaskAsyncEnumerable<TSource> source;
+        readonly Func<TSource, CancellationToken, UniTask<TKey>> keySelector;
+        readonly IEqualityComparer<TKey> comparer;
+
+        public DistinctAwaitCancellation(IUniTaskAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, UniTask<TKey>> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            this.source = source;
+            this.keySelector = keySelector;
+            this.comparer = comparer;
+        }
+
+        public IUniTaskAsyncEnumerator<TSource> GetAsyncEnumerator(CancellationToken cancellationToken = default)
+        {
+            return new Enumerator(source, keySelector, comparer, cancellationToken);
+        }
+
+        class Enumerator : AsyncEnumeratorAwaitSelectorBase<TSource, TSource, TKey>
+        {
+            readonly HashSet<TKey> set;
+            readonly Func<TSource, CancellationToken, UniTask<TKey>> keySelector;
+
+            public Enumerator(IUniTaskAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, UniTask<TKey>> keySelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
+
+                : base(source, cancellationToken)
+            {
+                this.set = new HashSet<TKey>(comparer);
+                this.keySelector = keySelector;
+            }
+
+            protected override UniTask<TKey> TransformAsync(TSource sourceCurrent)
+            {
+                return keySelector(sourceCurrent, cancellationToken);
+            }
+
+            protected override bool TrySetCurrentCore(TKey awaitResult, out bool terminateIteration)
+            {
+                if (set.Add(awaitResult))
+                {
+                    Current = SourceCurrent;
+                    terminateIteration = false;
+                    return true;
+                }
+                else
+                {
+                    terminateIteration = false;
+                    return false;
+                }
+            }
+        }
+    }
 }
\ No newline at end of file
diff --git a/src/UniTask.NetCore/Linq/_FileMaker.cs b/src/UniTask.NetCore/Linq/_FileMaker.cs
deleted file mode 100644
index 4f1b224..0000000
--- a/src/UniTask.NetCore/Linq/_FileMaker.cs
+++ /dev/null
@@ -1,51 +0,0 @@
-using Cysharp.Threading.Tasks;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Threading;
-using System.Threading.Tasks;
-
-namespace ___Dummy
-{
-
-    public interface IAsyncGrouping<TKey, TValue>
-    {
-    }
-
-
-    public interface IOrderedAsyncEnumerable<T>
-    {
-
-    }
-    public static partial class _FileMaker
-    {
-        // Buffer,Distinct, DistinctUntilChanged, Do, MaxBy, MinBy, Never,Return, Throw
-
-        
-
-
-
-
-
-
-
-
-
-
-
-        
-
-
-     
-
- 
-
-
-        
-
-
-    }
-
-
-}
-
diff --git a/src/UniTask.NetCoreTests/Linq/Sets.cs b/src/UniTask.NetCoreTests/Linq/Sets.cs
index 627c578..e730f61 100644
--- a/src/UniTask.NetCoreTests/Linq/Sets.cs
+++ b/src/UniTask.NetCoreTests/Linq/Sets.cs
@@ -32,10 +32,13 @@ namespace NetCoreTests.Linq
         [MemberData(nameof(array1))]
         public async Task Distinct(int[] array)
         {
-            var xs = await array.ToUniTaskAsyncEnumerable().Distinct().ToArrayAsync();
             var ys = array.Distinct().ToArray();
-
-            xs.Should().BeEquivalentTo(ys);
+            {
+                (await array.ToUniTaskAsyncEnumerable().Distinct().ToArrayAsync()).Should().BeEquivalentTo(ys);
+                (await array.ToUniTaskAsyncEnumerable().Distinct(x => x).ToArrayAsync()).Should().BeEquivalentTo(ys);
+                (await array.ToUniTaskAsyncEnumerable().DistinctAwait(x => UniTask.Run(() => x)).ToArrayAsync()).Should().BeEquivalentTo(ys);
+                (await array.ToUniTaskAsyncEnumerable().DistinctAwaitWithCancellation((x, _) => UniTask.Run(() => x)).ToArrayAsync()).Should().BeEquivalentTo(ys);
+            }
         }
 
         [Fact]
@@ -43,8 +46,22 @@ namespace NetCoreTests.Linq
         {
             foreach (var item in UniTaskTestException.Throws())
             {
-                var xs = item.Distinct().ToArrayAsync();
-                await Assert.ThrowsAsync<UniTaskTestException>(async () => await xs);
+                {
+                    var xs = item.Distinct().ToArrayAsync();
+                    await Assert.ThrowsAsync<UniTaskTestException>(async () => await xs);
+                }
+                {
+                    var xs = item.Distinct(x => x).ToArrayAsync();
+                    await Assert.ThrowsAsync<UniTaskTestException>(async () => await xs);
+                }
+                {
+                    var xs = item.DistinctAwait(x => UniTask.Run(() => x)).ToArrayAsync();
+                    await Assert.ThrowsAsync<UniTaskTestException>(async () => await xs);
+                }
+                {
+                    var xs = item.DistinctAwaitWithCancellation((x, _) => UniTask.Run(() => x)).ToArrayAsync();
+                    await Assert.ThrowsAsync<UniTaskTestException>(async () => await xs);
+                }
             }
         }