static void Main(string[] args)
{
//37
//decorate property
WriteLine("Question #37: Decorate property (Attribute)");
//36
//registry
//32
WriteLine("Question #32: Delegates");
//e) delegates are ideal for callback functions
//30
WriteLine("Question #30: string variable manipulations");
String s = "NY";
s.ToUpper();
s.ToLowerInvariant();
s.Clone();
s += "er";
WriteLine(s);
//ReadKey();
s.GetType(); //ctrl + e, h (inheritance hierarchy resharper)
//29
WriteLine("Question #29: casting, stack & heap, struts & class");
Rectangle r = new Rectangle();
WriteLine(r.Area);
//ReadKey();
//25
//which will compile successfully?
//24 generics C#
//23 expando object
WriteLine("Question #23: Expando object");
//22
WriteLine("Question #22: Generics, lambda op (=>), passing methods as parameters, implicit delegate");
//https://stackoverflow.com/questions/4015451/pass-a-method-as-a-parameter
Main22();
//ReadKey();
//21 again, HTTP 404 error occurred -- later as //27
WriteLine("Question #21 umm #27...: inheritance execution order");
MyTest.Main21Again();
//ReadKey();
//21
WriteLine("Question #21: nullables??");
City city = new City();
city.name = "Los Angeles";
string labelCity = city.name;
//string labelCountry = city.country.abbrev;
//a)
//string labelCountry = null;
//if(!city.country.abbrev.HasValue)
//b)
string labelCountryB = null;
if (city != null)
{
if (city.country == null)
{
labelCountryB = "US";
}
}
////ReadKey();
//c
string labelCountryC = city.country != null ? (city.country.abbrev != null ? city.country.abbrev : "US") : "US";
//d
//exception
//string labelCountryD = city.country.abbrev != null ? city.country.abbrev : "US";
//e
string labelCountryE = city?.country?.abbrev ?? "US";
WriteLine($"Name: {labelCity}");
WriteLine($"Country: {labelCountryB} {labelCountryC} {labelCountryE}");
ReadLine();
//e ?? double question mark is null-coalescing
//20
WriteLine("Question #20: More LINQ!");
int[] values = new int[] { 5, 4, 3, 4, 2, 5, 9, 4, 2, 4 };
var results = (from c in values orderby c select c * c).Distinct().Take(5);
foreach (var resultt in results)
{
WriteLine(resultt);
}
WriteLine("--");
//a
results = values.Distinct().OrderBy(f => f * f).Take(5).Select(c => c * c);
foreach (var resultt in results)
{
WriteLine(resultt);
}
WriteLine("--");
//b
IEnumerable <int> resultss = values.Select(c => c * c).Take(5).Distinct().OrderBy(f => f);
foreach (var resultt in resultss)
{
WriteLine(resultt);
}
WriteLine("--");
//c
IEnumerable <int> resultc = values.Select(c => c * c).OrderBy(f => f).Distinct().Take(5);
foreach (var resultt in resultc)
{
WriteLine(resultt);
}
WriteLine("--");
//d
IEnumerable <int> resultd = values.Distinct().OrderBy(f => f).Take(5).Select(c => c * c);
foreach (var resultt in resultd)
{
WriteLine(resultt);
}
WriteLine("--");
//cannot implicitly convert type...
//e
// int[] resulte = values.Select(c => c * c).Take(5).OrderBy(f => f);
// foreach (var resultt in resulte)
// {
// WriteLine(resultt);
// }
// WriteLine("--");
//ReadKey();
//19
ClassTester.Main19();
//ReadKey();
//17 -- skipped
WriteLine("Question #17: System Event Log");
//EventLogEntry.WriteEvent -- nope
//EventLog.WriteEntry("asdf");
//EventInstance.WriteEntry();
//EventLog.WriteEntry();
//16 - 1/2
WriteLine("Question #16: Bitwise Operators");
//https://stackoverflow.com/questions/4757447/understanding-the-behavior-of-a-single-ampersand-operator-on-integers
bool?a = null, b = null;
writeOutput(a & b);
writeOutput(a | b);
a = true;
writeOutput(a & b);
writeOutput(a | b);
b = false;
writeOutput(a & b);
writeOutput(a | b);
ReadLine();
//13
WriteLine("Question #13: (byte) casting");
int intValue = 250;
byte byteValue = (byte)intValue;
WriteLine(byteValue);
//ReadLine();
//12
WriteLine("Question #12: LINQ stuff");
//https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/linq/introduction-to-linq-queries
// The Three Parts of a LINQ Query:
// 1. Data source.
int[] numbers = new int[7] {
0, 1, 2, 3, 4, 5, 6
};
// 2. Query creation.
// numQuery is an IEnumerable<int>
var numQuery =
from num in numbers
where (num % 2) == 0
select num;
// 3. Query execution.
foreach (int num in numQuery)
{
Console.Write("{0,1} ", num);
}
// https://stackoverflow.com/questions/16012380/merge-2-arrays-using-linq
//join two arrays
int[] num1 = new int[] { 1, 55, 89, 43, 67, -3 };
int[] num2 = new int[] { 11, 35, 79, 23, 7, -10 };
//var result = from n1 in num1
// from n2 in num2
//select result;
var res = num1.Concat(num2).ToArray();
var result = num1.Union(num2).ToArray();
//var ress = num1.GroupJoin(num2).ToArray();
//12
WriteLine("Question #12: LINQ: OrderBy Group CrossJoin Intersect");
int[] array1 = { 1, 2, 3, 4 };
int[] array2 = { 3, 5, 5, 8 };
WriteLine(array1);
var resss = array1.Intersect(array2).ToArray();
//var res2 = array1.OrderBy() --- no
//var res3 = array1.Group??? --- incrorrect usage
//var res4 = array1.CrossJoin
foreach (var item in resss)
{
WriteLine(item.ToString());
}
//WriteLine(resss);
//ReadKey();
//11 2/2
WriteLine("Question #11: `ref` parameter");
StuffDoer.Main11(new string[6]);
//ReadKey();
//10 - part 2
WriteLine("Question #10: Derived Classes & Inheritance");
//B b = new B();
//A a = new C();
//E e = new A();
//C c = new E();
A aa = new E();
//7
WriteLine("Question #7: Queues");
//Queue<String>() q = new Queue();
/*
* tried applying this: https://www.tutorialspoint.com/csharp/csharp_queue.htm
* wouldn't compile
*
* Queue q = new Queue();
* q.Enqueue('A');
* q.Enqueue('M');
* q.Enqueue('G');
* q.Enqueue('W');
*
* WriteLine("Current queue: ");
* foreach (char c in q) Console.Write(c + " ");
*
* WriteLine();
* q.Enqueue('V');
* q.Enqueue('H');
* WriteLine("Current queue: ");
* foreach (char c in q) Console.Write(c + " ");
*
* WriteLine();
* WriteLine("Removing some values ");
* char ch = (char)q.Dequeue();
* WriteLine("The removed value: {0}", ch);
* ch = (char) q.Dequeue();
* WriteLine("The removed value: {0}", ch);
*
* //ReadKey();
*/
//5
var firstName = "";
WriteLine("Question #5: Exceptions");
try
{
}
catch (Exception ex) when(firstName == null)
{
WriteLine($"{firstName} cannot be null");
}
catch (Exception ex)
{
if (firstName == null)
{
WriteLine($"{nameof(firstName)} cannot be null");
}
}
// catch (Exception ex) when (firstName == null)
// {
// WriteLine($"{nameof(firstName)} cannot be null");
// }
// finally (Exception ex)
// {
//
// }
//ReadKey();
//1
WriteLine("Question #1: Overriding");
//which of the following are required to override Equals() method in C#?
Obj obj = new Obj();
WriteLine(obj.Equals(obj));
WriteLine(obj.Equals(null));
Obj obj1 = new Obj();
Obj obj2 = new Obj();
WriteLine(obj1.Equals(obj2));
ReadKey();
}