diff --git a/CSharp/C-xC-c.cs b/CSharp/C-xC-c.cs
new file mode 100644
index 0000000..721ff6e
--- /dev/null
+++ b/CSharp/C-xC-c.cs
@@ -0,0 +1,50 @@
+using System;
+using System.Runtime.CompilerServices;
+using System.Threading.Tasks;
+
+await foreach (var _ in await await await await await await await 0_0) ;
+
+static class Ext
+{
+    public static FizzBuzzEnumerator GetAsyncEnumerator(this int i) => new(i);
+
+    public static FizzBuzzAwaiter GetAwaiter(this int depth) => new(depth);
+
+    public static void FizzBuzz(int i) => Console.WriteLine((i % 15) switch
+    {
+        0 => "FizzBuzz",
+        5 or 10 => "Buzz",
+        3 or 6 or 9 or 12 => "Fizz",
+        _ => i.ToString()
+    });
+}
+
+record FizzBuzzAwaiter(int Depth) : INotifyCompletion
+{
+    public bool IsCompleted => true;
+
+    public int GetResult()
+    {
+        Ext.FizzBuzz(Depth);
+
+        return Depth + 1;
+    }
+
+    public void OnCompleted(Action continuation)
+    {
+    }
+}
+
+sealed class FizzBuzzEnumerator
+{
+    public int Current { get; private set; }
+
+    public FizzBuzzEnumerator(int current) => Current = current;
+
+    public ValueTask<bool> MoveNextAsync()
+    {
+        Ext.FizzBuzz(Current);
+
+        return new(Current++ < 100);
+    }
+}