MonthlyInventory report

InventoryTraker.Web/Utilities/IEnumerableExtensions.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace InventoryTraker.Web.Utilities
+{
+	public static class IEnumerableExtensions
+	{
+		public static IEnumerable<TResult> FullOuterGroupJoin<TA, TB, TKey, TResult>(
+			this IEnumerable<TA> a,
+			IEnumerable<TB> b,
+			Func<TA, TKey> selectKeyA,
+			Func<TB, TKey> selectKeyB,
+			Func<IEnumerable<TA>, IEnumerable<TB>, TKey, TResult> projection,
+			IEqualityComparer<TKey> cmp = null)
+		{
+			cmp = cmp ?? EqualityComparer<TKey>.Default;
+			var alookup = a.ToLookup(selectKeyA, cmp);
+			var blookup = b.ToLookup(selectKeyB, cmp);
+
+			var keys = new HashSet<TKey>(alookup.Select(p => p.Key), cmp);
+			keys.UnionWith(blookup.Select(p => p.Key));
+
+			var join = from key in keys
+				let xa = alookup[key]
+				let xb = blookup[key]
+				select projection(xa, xb, key);
+
+			return join;
+		}
+
+		public static IEnumerable<TResult> FullOuterJoin<TA, TB, TKey, TResult>(
+			this IEnumerable<TA> a,
+			IEnumerable<TB> b,
+			Func<TA, TKey> selectKeyA,
+			Func<TB, TKey> selectKeyB,
+			Func<TA, TB, TKey, TResult> projection,
+			TA defaultA = default(TA),
+			TB defaultB = default(TB),
+			IEqualityComparer<TKey> cmp = null)
+		{
+			cmp = cmp ?? EqualityComparer<TKey>.Default;
+			var alookup = a.ToLookup(selectKeyA, cmp);
+			var blookup = b.ToLookup(selectKeyB, cmp);
+
+			var keys = new HashSet<TKey>(alookup.Select(p => p.Key), cmp);
+			keys.UnionWith(blookup.Select(p => p.Key));
+
+			var join = from key in keys
+				from xa in alookup[key].DefaultIfEmpty(defaultA)
+				from xb in blookup[key].DefaultIfEmpty(defaultB)
+				select projection(xa, xb, key);
+
+			return join;
+		}
+	}
+}