chapter 13 exception handling: a deeper look
DESCRIPTION
Chapter 13 Exception Handling: A Deeper Look. Things Happen. Terminology. Exception Keywords. Running example. using System; using System.Collections.Generic ; using System.Linq ; using System.Text ; namespace UsingExceptions { class Program { - PowerPoint PPT PresentationTRANSCRIPT
Chapter 13Exception Handling:
A Deeper Look
1
Things Happen
2
Terminology
3
Exception Keywords
4
Running exampleusing System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace UsingExceptions
{
class Program
{
static void Main(string[] args)
{
int x = 10;
int y = 5;
int result;
try
{
result = x / y;
Console.WriteLine("The result is: {0}", result);
}
catch
{
Console.WriteLine("An error occurred! Better check the code!");
}
finally
{
Console.WriteLine("Just proving that this code always runs.");
}
Console.ReadLine();
}}}
5
Catching Specific Exceptions
6
Hierarchy
try
{
result = x / y;
Console.WriteLine("The result is: {0}", result);
}
catch (System.DivideByZeroException e)
{
Console.WriteLine("Whoops! You tried to divide by zero!");
Console.WriteLine(e.Message);
}
catch (System.ArithmeticException e)
{
Console.WriteLine("Whoops! You tried to divide by zero!");
Console.WriteLine(e.Message);
}
7
More Specific First try
{
result = x / y;
Console.WriteLine("The result is: {0}", result);
}
catch (System.ArithmeticException e)
{
Console.WriteLine("Whoops! You tried to divide by zero!");
Console.WriteLine(e.Message);
}
catch (System.DivideByZeroException e)
{
Console.WriteLine("Whoops! You tried to divide by zero!");
Console.WriteLine(e.Message);
}
finally
{
Console.WriteLine("Just proving that this code always runs.");
}
Console.ReadLine();
8
Exceptions are Objects
System.Exception Constructors Properties Hierarchy
http://msdn.microsoft.com/en-us/library/system.systemexception.aspx
System.Exception◦ System.ApplicationException (non fatal exceptions)◦ http://msdn.microsoft.com/en-us/library/system.applicationexception.aspx
9
Custom Exceptions
10
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace CustomExceptions
{
public class MyOwnException : Exception
{
public MyOwnException()
: base("Sergey is not welcomed here!") //Exception(string)
{
//this.HelpLink = "http://msdn.microsoft.com/en-us/library/system.exception.aspx";
}
}
class Program
{
static string GetName()
{
string s = Console.ReadLine();
if (s.Equals("Sergey"))
throw new MyOwnException();
return s;
}
11
static void Main(string[] args)
{
string theName;
try
{
theName = GetName();
Console.WriteLine("Hello {0}", theName);
}
catch (MyOwnException nje)
{
Console.WriteLine(nje.Message);
Console.WriteLine("For help, visit: {0}", nje.HelpLink);
}
finally
{
Console.WriteLine("Have a nice day!");
}
Console.ReadLine();
}
}
}
12
13.2 Example: Divide by Zero without Exception Handling
13
Re-throwing Exceptions
class Program
{
static void DoSomeMath()
{
int x = 10, y = 0;
int result;
try
{
result = x / y;
Console.WriteLine("Result is {0}", result);
}
catch
{
Console.WriteLine("Error in DoSomeMath()");
throw new ArithmeticException();
}
}
static void Main(string[] args)
{
try
{
DoSomeMath();
}
catch (ArithmeticException e)
{
Console.WriteLine("Hmm, there was an error in there, be careful!");
}
Console.ReadLine();
}
}14
15
13.3 Example: Handling DivideByZeroExceptions and FormatExceptions
16
17
18
19
20
13.4 .NET Exception Hierarchy
21
13.5 finally Block
22
23
24
25
26
27
28
29
30
31
13.7 Exception Properties
32
33
34
35
36
37
13.8 User-Defined Exception Classes
38
39
40
41
42
43