Using Core pattern for First, Last, Single.

Ix.NET/Source/System.Linq.Async/System/Linq/Operators/First.cs

@@ -15,7 +15,7 @@ namespace System.Linq
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
 
-            return First(source, CancellationToken.None);
+            return FirstCore(source, CancellationToken.None);
         }
 
         public static Task<TSource> First<TSource>(this IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
@@ -33,7 +33,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return First(source, predicate, CancellationToken.None);
+            return FirstCore(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> First<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
@@ -43,7 +43,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return source.Where(predicate).First(cancellationToken);
+            return FirstCore(source, predicate, cancellationToken);
         }
 
         public static Task<TSource> First<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate)
@@ -53,7 +53,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return First(source, predicate, CancellationToken.None);
+            return FirstCore(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> First<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)
@@ -63,7 +63,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return source.Where(predicate).First(cancellationToken);
+            return FirstCore(source, predicate, cancellationToken);
         }
 
         private static async Task<TSource> FirstCore<TSource>(IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
@@ -103,5 +103,15 @@ namespace System.Linq
 
             throw new InvalidOperationException(Strings.NO_ELEMENTS);
         }
+
+        private static Task<TSource> FirstCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
+        {
+            return source.Where(predicate).First(cancellationToken);
+        }
+
+        private static Task<TSource> FirstCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)
+        {
+            return source.Where(predicate).First(cancellationToken);
+        }
     }
 }

Ix.NET/Source/System.Linq.Async/System/Linq/Operators/FirstOrDefault.cs

@@ -15,7 +15,7 @@ namespace System.Linq
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
 
-            return FirstOrDefault(source, CancellationToken.None);
+            return FirstOrDefaultCore(source, CancellationToken.None);
         }
 
         public static Task<TSource> FirstOrDefault<TSource>(this IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
@@ -33,7 +33,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return FirstOrDefault(source, predicate, CancellationToken.None);
+            return FirstOrDefaultCore(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> FirstOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
@@ -43,7 +43,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return source.Where(predicate).FirstOrDefault(cancellationToken);
+            return FirstOrDefaultCore(source, predicate, cancellationToken);
         }
 
         public static Task<TSource> FirstOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate)
@@ -53,7 +53,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return FirstOrDefault(source, predicate, CancellationToken.None);
+            return FirstOrDefaultCore(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> FirstOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)
@@ -63,7 +63,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return source.Where(predicate).FirstOrDefault(cancellationToken);
+            return FirstOrDefaultCore(source, predicate, cancellationToken);
         }
 
         private static async Task<TSource> FirstOrDefaultCore<TSource>(IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
@@ -103,5 +103,15 @@ namespace System.Linq
 
             return default;
         }
+
+        private static Task<TSource> FirstOrDefaultCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
+        {
+            return source.Where(predicate).FirstOrDefault(cancellationToken);
+        }
+
+        private static Task<TSource> FirstOrDefaultCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)
+        {
+            return source.Where(predicate).FirstOrDefault(cancellationToken);
+        }
     }
 }

Ix.NET/Source/System.Linq.Async/System/Linq/Operators/Last.cs

@@ -15,7 +15,7 @@ namespace System.Linq
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
 
-            return Last(source, CancellationToken.None);
+            return LastCore(source, CancellationToken.None);
         }
 
         public static Task<TSource> Last<TSource>(this IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
@@ -33,7 +33,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return Last(source, predicate, CancellationToken.None);
+            return LastCore(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> Last<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
@@ -43,7 +43,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return source.Where(predicate).Last(cancellationToken);
+            return LastCore(source, predicate, cancellationToken);
         }
 
         public static Task<TSource> Last<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate)
@@ -53,7 +53,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return Last(source, predicate, CancellationToken.None);
+            return LastCore(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> Last<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)
@@ -63,7 +63,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return source.Where(predicate).Last(cancellationToken);
+            return LastCore(source, predicate, cancellationToken);
         }
 
         private static async Task<TSource> LastCore<TSource>(IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
@@ -113,5 +113,15 @@ namespace System.Linq
 
             throw new InvalidOperationException(Strings.NO_ELEMENTS);
         }
+
+        private static Task<TSource> LastCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
+        {
+            return source.Where(predicate).Last(cancellationToken);
+        }
+
+        private static Task<TSource> LastCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)
+        {
+            return source.Where(predicate).Last(cancellationToken);
+        }
     }
 }

Ix.NET/Source/System.Linq.Async/System/Linq/Operators/LastOrDefault.cs

@@ -15,7 +15,7 @@ namespace System.Linq
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
 
-            return LastOrDefault(source, CancellationToken.None);
+            return LastOrDefaultCore(source, CancellationToken.None);
         }
 
         public static Task<TSource> LastOrDefault<TSource>(this IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
@@ -33,7 +33,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return LastOrDefault(source, predicate, CancellationToken.None);
+            return LastOrDefaultCore(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> LastOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
@@ -53,7 +53,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return LastOrDefault(source, predicate, CancellationToken.None);
+            return LastOrDefaultCore(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> LastOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)
@@ -113,5 +113,15 @@ namespace System.Linq
 
             return default;
         }
+
+        private static Task<TSource> LastOrDefaultCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
+        {
+            return source.Where(predicate).LastOrDefault(cancellationToken);
+        }
+
+        private static Task<TSource> LastOrDefaultCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)
+        {
+            return source.Where(predicate).LastOrDefault(cancellationToken);
+        }
     }
 }

Ix.NET/Source/System.Linq.Async/System/Linq/Operators/Single.cs

@@ -15,7 +15,7 @@ namespace System.Linq
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
 
-            return Single(source, CancellationToken.None);
+            return SingleCore(source, CancellationToken.None);
         }
 
         public static Task<TSource> Single<TSource>(this IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
@@ -33,7 +33,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return Single(source, predicate, CancellationToken.None);
+            return SingleCore(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> Single<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
@@ -43,7 +43,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return source.Where(predicate).Single(cancellationToken);
+            return SingleCore(source, predicate, cancellationToken);
         }
 
         public static Task<TSource> Single<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate)
@@ -53,7 +53,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return Single(source, predicate, CancellationToken.None);
+            return SingleCore(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> Single<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)
@@ -63,7 +63,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return source.Where(predicate).Single(cancellationToken);
+            return SingleCore(source, predicate, cancellationToken);
         }
 
         private static async Task<TSource> SingleCore<TSource>(IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
@@ -101,5 +101,15 @@ namespace System.Linq
                 await e.DisposeAsync().ConfigureAwait(false);
             }
         }
+
+        private static Task<TSource> SingleCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
+        {
+            return source.Where(predicate).Single(cancellationToken);
+        }
+
+        private static Task<TSource> SingleCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)
+        {
+            return source.Where(predicate).Single(cancellationToken);
+        }
     }
 }

Ix.NET/Source/System.Linq.Async/System/Linq/Operators/SingleOrDefault.cs

@@ -15,7 +15,7 @@ namespace System.Linq
             if (source == null)
                 throw new ArgumentNullException(nameof(source));
 
-            return SingleOrDefault(source, CancellationToken.None);
+            return SingleOrDefaultCore(source, CancellationToken.None);
         }
 
         public static Task<TSource> SingleOrDefault<TSource>(this IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
@@ -33,7 +33,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return SingleOrDefault(source, predicate, CancellationToken.None);
+            return SingleOrDefaultCore(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> SingleOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
@@ -43,7 +43,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return source.Where(predicate).SingleOrDefault(cancellationToken);
+            return SingleOrDefaultCore(source, predicate, cancellationToken);
         }
 
         public static Task<TSource> SingleOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate)
@@ -53,7 +53,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return SingleOrDefault(source, predicate, CancellationToken.None);
+            return SingleOrDefaultCore(source, predicate, CancellationToken.None);
         }
 
         public static Task<TSource> SingleOrDefault<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)
@@ -63,7 +63,7 @@ namespace System.Linq
             if (predicate == null)
                 throw new ArgumentNullException(nameof(predicate));
 
-            return source.Where(predicate).SingleOrDefault(cancellationToken);
+            return SingleOrDefaultCore(source, predicate, cancellationToken);
         }
 
         private static async Task<TSource> SingleOrDefaultCore<TSource>(IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
@@ -101,5 +101,15 @@ namespace System.Linq
 
             throw new InvalidOperationException(Strings.MORE_THAN_ONE_ELEMENT);
         }
+
+        private static Task<TSource> SingleOrDefaultCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
+        {
+            return source.Where(predicate).SingleOrDefault(cancellationToken);
+        }
+
+        private static Task<TSource> SingleOrDefaultCore<TSource>(IAsyncEnumerable<TSource> source, Func<TSource, Task<bool>> predicate, CancellationToken cancellationToken)
+        {
+            return source.Where(predicate).SingleOrDefault(cancellationToken);
+        }
     }
 }