public void Chaining_Dictionary() { var dict = new System.Collections.Generic.Dictionary <int, int> { [1] = 2, [3] = 4 }; var sortedDict = new System.Collections.Generic.SortedDictionary <int, int> { [1] = 2, [3] = 4 }; Assert.IsTrue(dict.Contains(dict.First())); Assert.IsTrue(dict.Contains(dict.First(), null)); Assert.IsTrue(sortedDict.Contains(sortedDict.First())); Assert.IsTrue(sortedDict.Contains(sortedDict.First(), null)); }