1 files changed, 32 insertions, 0 deletions
diff --git a/src/csharp/GrpcApi/RecordingObserver.cs b/src/csharp/GrpcApi/RecordingObserver.cs
new file mode 100644
index 0000000000..8ba3787905
--- /dev/null
+++ b/src/csharp/GrpcApi/RecordingObserver.cs
@@ -0,0 +1,32 @@
+using System;
+using System.Threading.Tasks;
+using System.Collections.Generic;
+
+namespace math
+{
+    public class RecordingObserver<T> : IObserver<T>
+    {
+        TaskCompletionSource<List<T>> tcs = new TaskCompletionSource<List<T>>();
+        List<T> data = new List<T>();
+
+        public void OnCompleted()
+        {
+            tcs.SetResult(data);
+        }
+
+        public void OnError(Exception error)
+        {
+            tcs.SetException(error);
+        }
+
+        public void OnNext(T value)
+        {
+            data.Add(value);
+        }
+
+        public Task<List<T>> ToList() {
+            return tcs.Task;
+        }
+    }
+}
+