面试题与答案

Private

No

Only one of them is run, that is the one marked (public) static, e.g:
public static void Main(string[] args)
{
//
// TODO: Add code to start application here
//
}
private void Main(string[] args, int i)
{
}

void and int

An out parameter allows an instance of a parameter object to be made inside a method.
Reference parameters must be initialised but out gives a reference to an uninstanciated
object.

using System;
namespace Console1
{
class Class1
{
static void Main(string[] args)
{
ParamsMethod(1,"example");
ParamsMethod(1,2,3,4);
Console.ReadLine();
}
static void ParamsMethod(params object[] list)
{
foreach (object o in list)
{
Console.WriteLine(o.ToString());
}
}
}
}

No

The main reason we use delegates is for use in event driven programming.

Asynchronous

Objects publish events to which other applications subscribe. When the publisher raises
an event all subscribers to that event are notified.

Yes, also - here's some code for a publisher with multiple subscribers.
using System;
namespace Console1
{
class Class1
{
delegate void myDelegate(int parameter1);
static event myDelegate myEvent;
static void AStaticMethod(int param1)
{
Console.WriteLine(param1);
}
static void Main(string[] args)
{
MyClass myInstance = new MyClass();
myEvent += new myDelegate(myInstance.AMethod);
myEvent += new myDelegate(AStaticMethod);
myEvent(1); //both functions will be run.
Console.ReadLine();
}
}
class MyClass
{
public void AMethod(int param1)
{
Console.WriteLine(param1);
}
}
}
Another example:
using System;
using System.Threading;
namespace EventExample
{
public class Clock
{
public delegate void TwoSecondsPassedHandler(object clockInstance,
TimeEventArgs time);
//The clock publishes an event that others subscribe to
public event TwoSecondsPassedHandler TwoSecondsPassed;
public void Start()
{
while(true)
{
Thread.Sleep(2000);
//Raise event
TwoSecondsPassed(this, new TimeEventArgs(1));
}
}
}
public class TimeEventArgs : EventArgs
{
public TimeEventArgs(int second)
{
seconds += second;
instanceSeconds = seconds;
}
private static int seconds;
public int instanceSeconds;
}
public class MainClass
{
static void Main(string[] args)
{
Clock cl = new Clock();
// add some subscribers
cl.TwoSecondsPassed += new
Clock.TwoSecondsPassedHandler(Subscriber1);
cl.TwoSecondsPassed += new
Clock.TwoSecondsPassedHandler(Subscriber2);
cl.Start();
Console.ReadLine();
}
public static void Subscriber1(object clockInstance, TimeEventArgs time)
{
Console.WriteLine("Subscriber1:" + time.instanceSeconds);
}
public static void Subscriber2(object clockInstance, TimeEventArgs time)
{
Console.WriteLine("Subscriber2:" + time.instanceSeconds);
}
}
}

Stack

Yes

When converting from a smaller numeric type into a larger one the cast is implicit. An
example of when an explicit cast is needed is when a value may be truncated.

Allocate a block of memory on the stack (used in unsafe mode).