refactor: add removeAll method to observable collection

Client/Application/Extensions/ObservableCollectionExtensions.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Client.Application.Extensions
+{
+    public static class ObservableCollectionExtensions
+    {
+        public static void RemoveAll<T>(this ObservableCollection<T> collection,
+                                                           Func<T, bool> condition)
+        {
+            for (int i = collection.Count - 1; i >= 0; i--)
+            {
+                if (condition(collection[i]))
+                {
+                    collection.RemoveAt(i);
+                }
+            }
+        }
+    }
+}