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));
}