Reordering ToDictionary overloads.

Ix.NET/Source/System.Interactive.Async/ToDictionary.cs

@@ -10,30 +10,24 @@ namespace System.Linq
 {
     public static partial class AsyncEnumerable
     {
-        public static Task<Dictionary<TKey, TElement>> ToDictionary<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer)
+        public static Task<Dictionary<TKey, TSource>> ToDictionary<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (keySelector == null)
                 throw new ArgumentNullException(nameof(keySelector));
-            if (elementSelector == null)
-                throw new ArgumentNullException(nameof(elementSelector));
-            if (comparer == null)
-                throw new ArgumentNullException(nameof(comparer));
 
-            return ToDictionary(source, keySelector, elementSelector, comparer, CancellationToken.None);
+            return ToDictionary(source, keySelector, CancellationToken.None);
         }
 
-        public static Task<Dictionary<TKey, TElement>> ToDictionary<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector)
+        public static Task<Dictionary<TKey, TSource>> ToDictionary<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, CancellationToken cancellationToken)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (keySelector == null)
                 throw new ArgumentNullException(nameof(keySelector));
-            if (elementSelector == null)
-                throw new ArgumentNullException(nameof(elementSelector));
 
-            return ToDictionary(source, keySelector, elementSelector, CancellationToken.None);
+            return source.ToDictionary(keySelector, x => x, EqualityComparer<TKey>.Default, cancellationToken);
         }
 
         public static Task<Dictionary<TKey, TSource>> ToDictionary<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
@@ -48,17 +42,19 @@ namespace System.Linq
             return ToDictionary(source, keySelector, comparer, CancellationToken.None);
         }
 
-        public static Task<Dictionary<TKey, TSource>> ToDictionary<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector)
+        public static Task<Dictionary<TKey, TSource>> ToDictionary<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (keySelector == null)
                 throw new ArgumentNullException(nameof(keySelector));
+            if (comparer == null)
+                throw new ArgumentNullException(nameof(comparer));
 
-            return ToDictionary(source, keySelector, CancellationToken.None);
+            return source.ToDictionary(keySelector, x => x, comparer, cancellationToken);
         }
 
-        public static Task<Dictionary<TKey, TElement>> ToDictionary<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
+        public static Task<Dictionary<TKey, TElement>> ToDictionary<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
@@ -66,18 +62,8 @@ namespace System.Linq
                 throw new ArgumentNullException(nameof(keySelector));
             if (elementSelector == null)
                 throw new ArgumentNullException(nameof(elementSelector));
-            if (comparer == null)
-                throw new ArgumentNullException(nameof(comparer));
 
-            return source.Aggregate(
-                new Dictionary<TKey, TElement>(comparer),
-                (d, x) =>
-                {
-                    d.Add(keySelector(x), elementSelector(x));
-                    return d;
-                },
-                cancellationToken
-            );
+            return ToDictionary(source, keySelector, elementSelector, CancellationToken.None);
         }
 
         public static Task<Dictionary<TKey, TElement>> ToDictionary<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, CancellationToken cancellationToken)
@@ -92,26 +78,40 @@ namespace System.Linq
             return source.ToDictionary(keySelector, elementSelector, EqualityComparer<TKey>.Default, cancellationToken);
         }
 
-        public static Task<Dictionary<TKey, TSource>> ToDictionary<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
+        public static Task<Dictionary<TKey, TElement>> ToDictionary<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (keySelector == null)
                 throw new ArgumentNullException(nameof(keySelector));
+            if (elementSelector == null)
+                throw new ArgumentNullException(nameof(elementSelector));
             if (comparer == null)
                 throw new ArgumentNullException(nameof(comparer));
 
-            return source.ToDictionary(keySelector, x => x, comparer, cancellationToken);
+            return ToDictionary(source, keySelector, elementSelector, comparer, CancellationToken.None);
         }
 
-        public static Task<Dictionary<TKey, TSource>> ToDictionary<TSource, TKey>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, CancellationToken cancellationToken)
+        public static Task<Dictionary<TKey, TElement>> ToDictionary<TSource, TKey, TElement>(this IAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
         {
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
             if (keySelector == null)
                 throw new ArgumentNullException(nameof(keySelector));
+            if (elementSelector == null)
+                throw new ArgumentNullException(nameof(elementSelector));
+            if (comparer == null)
+                throw new ArgumentNullException(nameof(comparer));
 
-            return source.ToDictionary(keySelector, x => x, EqualityComparer<TKey>.Default, cancellationToken);
+            return source.Aggregate(
+                new Dictionary<TKey, TElement>(comparer),
+                (d, x) =>
+                {
+                    d.Add(keySelector(x), elementSelector(x));
+                    return d;
+                },
+                cancellationToken
+            );
         }
     }
 }