public void GetOrUpdateTest()
{
var dict = new Dictionary <string, int> {
{ "a", 1 }, { "b", 2 }
};
var rs = dict.GetOrUpdate("c", 3);
Assert.AreEqual(3, rs);
Assert.AreEqual(3, dict["c"]);
var rs2 = dict.GetOrUpdate("a", 0);
Assert.AreEqual(1, rs2);
Assert.AreEqual(1, dict["a"]);
var readOnlyDict = new ReadOnlyDictionary <string, int>(new Dictionary <string, int> {
{ "a", 1 }, { "b", 2 }
});
Assert.ThrowsException <NotSupportedException>(() => readOnlyDict.GetOrUpdate("c", 3));
Assert.ThrowsException <ArgumentNullException>(() => readOnlyDict.AddOrUpdate(null, 3));
}