Create README.md

README.md

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+# OneOf.Linq
+
+Extensions for https://github.com/mcintyre321/OneOf that expose `XOrResonWhyNot` extension methods for LINQ.
+
+# Demonstration
+
+Without library:
+```C#
+var myList1 = new object[] { 1, null };
+var myList2 = new object[] { };
+
+object last1 = myList1.LastOrDefault();
+object last2 = myList2.LastOrDefault();
+
+// Oh no! This fails because both are null!
+// Even worse when you have value types (like int) and
+// can't tell the difference between 0 and 'no-values'
+Assert.AreNotEqual(last1, last2, "because one had a last and one did not");
+```
+
+With library:
+```C#
+var myList1 = new object[] { 1, null };
+var myList2 = new object[] { };
+
+OneOf<object, NoElements> last1 = myList1.LastOrReasonWhyNot();
+OneOf<object, NoElements> last2 = myList2.LastOrReasonWhyNot();
+
+// Yay! it works!
+Assert.AreNotEqual(last1, last2, "because one had a last and one did not");
+
+Assert.IsTrue(last1.HasValue());
+Assert.IsFalse(last2.HasValue());
+
+Assert.AreEqual(null, last1.Value());
+Assert.AreEqual(default(NoElements), last2.WhyNot());
+```