Merge pull request #77 from Azure/75-trigger-publisher-on-configurati…

…on-file-change

75 trigger publisher on configuration file change

tools/code/common/Enumerable.cs

@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace common;
+
+public static class IEnumerableModule
+{
+    /// <summary>
+    /// Applies <paramref name="f"/> to <paramref name="enumerable"/> items and filters out
+    /// null results.
+    /// </summary>
+    public static IEnumerable<T2> Choose<T, T2>(this IEnumerable<T> enumerable, Func<T, T2?> f) where T2 : class
+    {
+        return from t in enumerable
+               let t2 = f(t)
+               where t2 is not null
+               select t2;
+    }
+
+    /// <summary>
+    /// Applies <paramref name="f"/> to <paramref name="enumerable"/> items and filters out
+    /// null results.
+    /// </summary>
+    public static IEnumerable<T2> Choose<T, T2>(this IEnumerable<T> enumerable, Func<T, T2?> f) where T2 : struct
+    {
+        return from t in enumerable
+               let t2 = f(t)
+               where t2 is not null
+               select t2.Value;
+    }
+}