1) Overloading
What is displayed, and why?
using System;
class Base
{
public virtual void Foo(int x)
{
Console.WriteLine ("Base.Foo(int)");
}
}
class Derived : Base
{
public override void Foo(int x)
{
Console.WriteLine ("Derived.Foo(int)");
}
public void Foo(object o)
{
Console.WriteLine ("Derived.Foo(object)");
}
}
class Test
{
static void Main()
{
Derived d = new Derived();
int i = 10;
d.Foo(i);
}
}
class Base
{
public virtual void Foo(int x)
{
Console.WriteLine ("Base.Foo(int)");
}
}
class Derived : Base
{
public override void Foo(int x)
{
Console.WriteLine ("Derived.Foo(int)");
}
public void Foo(object o)
{
Console.WriteLine ("Derived.Foo(object)");
}
}
class Test
{
static void Main()
{
Derived d = new Derived();
int i = 10;
d.Foo(i);
}
}
2) Order! Order!
What will be displayed, why?
using System;
class Foo
{
static Foo()
{
Console.WriteLine ("Foo");
}
}
class Bar
{
static int i = Init();
static int Init()
{
Console.WriteLine("Bar");
return 0;
}
}
class Test
{
static void Main()
{
Foo f = new Foo();
Bar b = new Bar();
}
}
class Foo
{
static Foo()
{
Console.WriteLine ("Foo");
}
}
class Bar
{
static int i = Init();
static int Init()
{
Console.WriteLine("Bar");
return 0;
}
}
class Test
{
static void Main()
{
Foo f = new Foo();
Bar b = new Bar();
}
}
3) Silly arithmetic
Computers are meant to be good at arithmetic, aren't they? Why does this print "False"?
double d1 = 1.000001;
double d2 = 0.000001;
Console.WriteLine((d1-d2)==1.0);
double d2 = 0.000001;
Console.WriteLine((d1-d2)==1.0);
4) Print, print, print...
Here's some code using the anonymous method feature of C# 2. What does it do?
using System;
using System.Collections.Generic;
class Test
{
delegate void Printer();
static void Main()
{
List printers = new List();
for (int i=0; i < 10; i++) { printers.Add(delegate { Console.WriteLine(i); });
}
foreach (Printer printer in printers)
{
printer();
}
}
}
using System.Collections.Generic;
class Test
{
delegate void Printer();
static void Main()
{
List
for (int i=0; i < 10; i++) { printers.Add(delegate { Console.WriteLine(i); });
}
foreach (Printer printer in printers)
{
printer();
}
}
}
5) Literally nothing wrong with the compiler here...
Should this code compile? Does it? What does it mean?
using System;
class Test
{
enum Foo { Bar, Baz };
static void Main()
{
Foo f = 0.0;
Console.WriteLine(f);
}
}
class Test
{
enum Foo { Bar, Baz };
static void Main()
{
Foo f = 0.0;
Console.WriteLine(f);
}
}
More along the same lines...
using System;
class Test
{
enum Foo { Bar, Baz };
const int One = 1;
const int Une = 1;
static void Main()
{
Foo f = One-Une;
Console.WriteLine(f);
}
}
class Test
{
enum Foo { Bar, Baz };
const int One = 1;
const int Une = 1;
static void Main()
{
Foo f = One-Une;
Console.WriteLine(f);
}
}
6) Type inference a-go-go
Once again, work out what will be printed, and why?
using System;
class Test
{
static void Main()
{
Foo("Hello");
}
static void Foo(object x)
{
Console.WriteLine("object");
}
static void Foo(params T[] x)
{
Console.WriteLine("params T[]");
}
}
class Test
{
static void Main()
{
Foo("Hello");
}
static void Foo(object x)
{
Console.WriteLine("object");
}
static void Foo
{
Console.WriteLine("params T[]");
}
}
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