1 files changed, 40 insertions, 0 deletions
diff --git a/dsa/FireBase/ObservableExtensions.cs b/dsa/FireBase/ObservableExtensions.cs
new file mode 100644
index 0000000..bc46261
--- /dev/null
+++ b/dsa/FireBase/ObservableExtensions.cs
@@ -0,0 +1,40 @@
+using System;
+using System.Collections.ObjectModel;
+using Firebase.Database.Streaming;
+
+namespace Firebase.Database
+{
+    /// <summary>
+    ///     Extensions for <see cref="IObservable{T}" />.
+    /// </summary>
+    public static class ObservableExtensions
+    {
+        /// <summary>
+        ///     Starts observing on given firebase observable and propagates event into an <see cref="ObservableCollection{T}" />.
+        /// </summary>
+        /// <param name="observable"> The observable. </param>
+        /// <typeparam name="T"> Type of entity. </typeparam>
+        /// <returns> The <see cref="ObservableCollection{T}" />. </returns>
+        public static ObservableCollection<T> AsObservableCollection<T>(this IObservable<FirebaseEvent<T>> observable)
+        {
+            var collection = new ObservableCollection<T>();
+
+            observable.Subscribe(f =>
+            {
+                if (f.EventType == FirebaseEventType.InsertOrUpdate)
+                {
+                    var i = collection.IndexOf(f.Object);
+                    if (i >= 0) collection.RemoveAt(i);
+
+                    collection.Add(f.Object);
+                }
+                else
+                {
+                    collection.Remove(f.Object);
+                }
+            });
+
+            return collection;
+        }
+    }
+}
+\ No newline at end of file